Dynamic conditions for large shallow intraslab earthquakes

Dynamic conditions for large shallow intraslab earthquakes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Dynamic conditions for large shallow intraslab earthquakes Masaki Yoshida This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4598015/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 09 Oct, 2024 Read the published version in Geoscience Letters → Version 1 posted 9 You are reading this latest preprint version Abstract Large shallow intraslab earthquakes (LSIEs) of over magnitude-7 rarely occur at shallower depths (≤ 60 km) in the subducting plates of the circum-Pacific and northern margin of the Australian Plate off Indonesia. Research has suggested that most LSIEs occur under surface tectonic conditions with a lateral stress gradient across the back-arc to the fore-arc on the overriding plate based on seismological and geological evidence from trenches. In this study, dynamic conditions for the occurrence of LSIEs were studied using the intraslab stress state, stress state of the overriding plate, motion speed of overriding and subducting plates, and trench migration speed determined by geodesic plate motion models. LSIEs prefer tectonic conditions under (1) a nearly neutral stress state in the back-arc, (2) a compressional stress state in the fore-arc, and (3) down-dip tension in the shallower part of the subducting plate. In particular, the trenches of major subduction zones where LSIEs occur have a neutral back-arc stress state as deduced from analyses of plate motion geodetic data. The results suggest that the Earth’s subduction zones can be classified into four categories. This categorization is informed by the behavior of underlying mantle flow, i.e., the magnitude of slab suction flow in the mantle under the subducting plates and the scale of return flow in the mantle wedge under the overriding plates, which varies the combination of stress states in the fore-arc, back-arc, and intraslab. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Large shallow intraslab earthquakes (LSIEs) of over magnitude-7 rarely occur at depths of ≤ 60 km (Preston et al., 2002 ; Seno and Yoshida, 2004 ). A M w 8.2 intraslab earthquake occurred in Chiapas, Mexico, on September 8, 2017 (Ye et al., 2017 ), which caused severe damage. Since LSIEs cause severe damage owing to the shallower depths of their epicenters, deep understanding of the mechanism of LSIEs can aid hazard assessments in areas near related subduction zones. Furthermore, the occurrence of LSIEs possibly depends on dynamic interactions between not only the subducting and overriding plates but also between these plates and underlying mantle flow. Therefore, the study of the dynamic conditions for LSIEs is key to understanding the relationship between the Earth’s surface activity, which is directly observable, and the Earth’s deep activity, which is not directly observable and indirectly studied by, for example, numerical simulations, seismic tomography, and geochemical analyses of mantle rocks. Based on the focal mechanisms of earthquakes, slab stress, and the stress state of overriding plates near the 20 events listed by the Global CMT catalog (Dziewonski et al., 1981 ; Ekström et al., 2012 ) and individual studies, Seno and Yoshida ( 2004 ) concluded that LSIEs occur in tectonic environments with down-dip tension (DDT) in the shallower part of the subducting plate and tensional back-arc stress, except for a few events. However, their analyses were based on a dataset from seismological and geological evidence and not on geodetic observation of plate motion, and they did not clearly discuss the phenomenon in terms of the relationship between surface observation and underlying mantle dynamics. Geodetic information of plate motion is useful for estimating not only absolute velocity and motion but also the deformation rate of the plate interior near a trench. In particular, such geodetic information produces a quantitative estimation of the stress state of the subducting and overlying plates and complements information from geological observations and focal mechanisms (e.g., Lallemand et al., 2005 ; Lallemand et al., 2008 ). In this study, I investigated dynamic conditions for LSIEs using a dataset for the intraslab stress state, stress state of the overriding plate, motion speed of the overriding and subducting plates, and trench migration speed (i.e., trench advance or retreat) determined by geodesic observation. Dynamic conditions for large shallow intraslab earthquakes Seno and Yoshida ( 2004 ) studied events with depths of 20–60 km, because events at depths shallower than 20 km cannot be distinguished from outer-rise events, and those deeper than 60 km are caused by unbending processes in the elastic core of the plate (Engdahl and Scholz, 1977 ) and thermal stress constrained by slab morphology (Hamaguchi et al., 1977 ). Table 1 is a modified list of LSIEs based on the study by Seno and Yoshida ( 2004 ) and updated information. This list was constructed mostly from the studies by Preston et al. ( 2002 ) and Wong ( 2005 ) for the Cascadia Trench, Ye et al. ( 2017 ) for the Mexico Trench, Mallick et al. ( 2017 ) for the Sumatra–Andaman Trench, and Harada and Ishibashi ( 2008 ) for the Mariana Trench, in addition to information from the Global CMT catalog and other individual studies. Table 1 List of large shallow intraslab earthquakes. No. Event Trench Origin (year/month/day) Epicenter M W d Faulting parameter Slab age References Lat. Lon. ϕ δ λ 1 Sumatra Sumatra 2000/06/04 −4.73 101.94 7.8 44 92 55 152 60–72 Seno and Yoshida ( 2004 ) 2 Sumatra Andaman 2010/06/12 7.85 91.65 7.5 33 115 63 149 69–86 Mallick et al. ( 2017 ) 3 Manila Luzon (Manila) 1999/12/11 15.87 119.64 7.2 35 112 13 −169 18–32 Seno and Yoshida ( 2004 ) 4 Kii-Yamato Nankai 1899/03/07 34.1 136.1 7.0 45 – – – 17–21 Utsu ( 1982 ) 5 Geiyo 2001/03/24 34.13 132.71 6.8 47 181 57 −67 Preston et al. ( 2002 ); Seno and Yoshida ( 2004 ) 6 Geiyo 1905/01/02 34.1 132.5 7.2 50 – – – Utsu ( 1982 ) 7 Yoshino 1952/07/18 34.5 135.8 6.8 60 – – – Utsu ( 1982 ) 8 Hyuganda 1931/11/02 32.2 132.1 7.1 40 – – – Utsu ( 1982 ) 9 Guam Mariana 1993/08/08 12.98 144.80 7.7 45 238 24 82 156 Harada and Ishibashi ( 2008 ) 10 Hokkaido-Toho-Oki Kuril 1994/10/04 43.42 146.81 8.3 33 158 41 24 118–128 Utsu ( 1982 ) 11 Etorofu-Oki 1958/11/07 44.38 148.58 8.3 32 – – – Harada and Ishibashi ( 2000 ) 12 Kodiak Is. W. and E. Alaska 1999/12/06 57.35 −154.35 7.0 36 357 63 −180 40–52 Utsu ( 1982 ) 13 Nisqually Cascadia 2001/02/28 47.14 −122.53 6.8 47 176 17 −96 10–11 Preston et al. ( 2002 ); Wong ( 2005 ) 14 Seattle-Tacoma 1965/04/29 47.38 −122.31 6.7 60 344 70 −75 Preston et al. ( 2002 ); Wong ( 2005 ) 15 Olympia 1949/04/13 47.17 −122.62 7.1 54 14 82 −135 Baker and Langston ( 1987 ); Preston et al. ( 2002 ); Wong ( 2005 ) 16 Chiapas Mexico 2017/09/08 15.34 -94.62 8.2 50 148 13 -83 8–15 Ye et al. ( 2017 ) 17 Oaxaca 1999/09/30 15.70 −96.96 7.4 47 102 42 −103 Ye et al. ( 2017 ) 18 Oaxaca 1931/01/15 16.4 −96.3 7.7 40 90 34 −90 Ye et al. ( 2017 ) 19 Oaxaca 1907/04/15 16.51 −97.30 7.6 30 – – – Ye et al. ( 2017 ), USGS 20 Michoacán 1997/01/11 18.34 −102.58 7.1 40 175 18 −28 Seno and Yoshida ( 2004 ) 21 Guerrero 1957/07/28 17.06 −99.09 7.6 38 – – – Ye et al. ( 2017 ), USGS 22 El Salvador Costa-Rica 1982/06/19 12.65 −88.97 7.3 52 102 25 −106 22–28 Seno and Yoshida ( 2004 ) 23 El Salvador 2001/01/13 12.97 −89.13 7.7 56 121 35 −95 Preston et al. ( 2002 ) 24 Peru Peru 1970/05/31 −9.18 −78.82 7.9 43 160 37 −90 31–46 Abe ( 1972 ) 25 Taltal N. Chile 1965/02/23 −25.67 −70.79 7.0 60 16 86 −78 52–53 Utsu ( 1982 ) 26 Vanuatu S. and. N. New Hebrides 1994/07/13 −16.50 167.35 7.1 25 272 42 2 45–60 Utsu ( 1982 ) 27 Vanuatu 1981/07/06 −22.31 170.90 7.5 58 345 30 −179 Utsu ( 1982 ) Symbols: d : depth; δ : dip; λ : rake; ϕ : strike. Abbreviations: USGS: United States Geological Survey webpage: https://earthquake.usgs.gov/earthquakes/ . The largest LSIEs were the 1994 Hokkaido–Toho–Oki Earthquake and the 1958 Etrofu–Oki Earthquake, which occurred in the Kuril Trench, with a magnitude of 8.3. Although the latter was considered to be an interplate earthquake (Utsu, 1972 ), more recent seismic analyses have suggested that this was an intraslab earthquake (Harada and Ishibashi, 2000 ). Lallemand et al. ( 2008 ) presented the absolute velocity of the subducting plates, overriding plates, and trench migration ( V sub , V up , and V t , respectively) on 166 transects at every 2° along subduction zones based on the three plate motion reference frames, i.e., HS3 (Gripp and Gordon, 2002 ), SB04 (Becker, 2006 ; Steinberger et al., 2004 ), and NNR (DeMets et al., 1994 ; Gripp and Gordon, 2002 ). In their definition, the relative value of back-arc deformation is defined by v d ≡ V t − V up , where negative and positive v d values indicate back-arc compression (i.e., shortening) and extension (i.e., spreading), respectively (Fig. 2 ). In this paper, the relative value of fore-arc deformation is defined by v c ≡ V sub − V up , where negative and positive v c values indicate fore-arc compression (i.e., shortening) and extension (i.e., spreading) respectively (Fig. 2 ). To determine the relationship between the back- and fore-arc stress states, I plotted v d -versus- v c diagrams of the 166 trenches in the three reference frames (Fig. 3 c and Figs. S1c and S2c in the supplementary material). On the other hand, Fig. 3 d and Figs. S1d and S2d in the supplementary material show the v d -versus- v c diagram of trenches where LSIEs occur; I identified 48 trenches relating to LSIEs, including the Sumatra, Andaman, Luzon (Manila), Mariana, Kuril, Alaska, Cascadia, Mexico, Costa Rica, Peru, Northern Chile, and New Hebrides Trenches as well as the Nankai Trough (Table 1 ). These 48 trenches include 13, 26, and 9 trenches of compressional, neutral, and extensional regimes in the back-arc, respectively, as deduced from research on the focal mechanisms of earthquakes (Lallemand et al., 2005 ; Lallemand et al., 2008 ). It was found that the distribution of these plots did not depend on the reference frames, although the V sub -versus- V up diagrams (Fig. 3 a and Figs. S1a and S2a in the supplementary material) and the V sub -versus- V t diagram (note that V up ~ V t in many trenches (Lallemand et al., 2008 )) (Fig. 3 b and Figs. S1b and S2b in the supplementary material) show variations in the three reference frames. Because the velocities of the subducting and overriding plates and the speed of trench migration in each trench depend on the reference frame (e.g., Heuret and Lallemand, 2005 ; Schellart et al., 2008 ), it was difficult to quantitatively determine the effects of the relative plate motion of the subducting and overriding plates on the stress states of the back- and fore-arcs. Therefore, I focused only on the dynamic conditions for LSIEs in terms of the relationship between the back- and fore-arc stress states from the geodetic data and intraslab stress from the focal mechanisms. Figure 3 d demonstrates that LSIEs are found for a wide range of v d values, varying from −4.44 cm yr − 1 to + 2.06 cm yr − 1 , and many trenches (29 of 48) are neutral, i.e., v d = 0.0 cm yr − 1 . However, the 10 trenches with v d < 0 are a part of the southern and northern New Hebrides, southern Mariana, and Andaman Trenches, which are minor compared to other trenches in the Western Pacific and northern Australian Plate off Indonesia. The five trenches with v d > 0 are a part of the Luzon (Manila) and Northern Chile Trenches, which are relatively minor compared to other major trenches. Therefore, I concluded that LSIEs prefer tectonic conditions under (1) a nearly neutral stress state in the back-arc and (2) a compressional stress state in the fore-arc from the present analyses, and (3) DDT in the shallower part of the subducting plate, as previously suggested by Seno and Yoshida ( 2004 ). Four categories of subduction zones Subduction zone systems have geological, seismological, and geodynamic characteristics. For example, Conrad et al. ( 2004 ) classified trenches in subduction zone systems into two types in terms of the mechanical coupling between the surface and subducting plates. One type includes trenches under conditions with a strong mechanical coupling between these plates, such as the South Chile, Aleutian, and Japan, and Kuril–Kamchatka Trenches (Fig. 6a of Conrad et al. ( 2004 )). In this type of subduction zone system, the slab pull force is decoupled or weakly coupled with the surface plate, because the convergent continent–ocean margin is considered to be mechanically damaged in the shallower part of the subducting slab. The other type includes trenches under conditions with a weak mechanical coupling between them, such as the Tonga–Kermadec, Java–Andaman, and Izu–Bonin (Ogasawara)–Mariana Trenches (Fig. 6b of Conrad et al. ( 2004 )). In this type, the slab pull force is strongly coupled with the surface plate because there is no mechanical damage in the shallower part of subducting slab when the continental plate moves backward from the trench (see Yoshida ( 2017 ) for details). The above classification is used in Fig. 4 to demonstrate the proposed four categories of subduction zone systems in terms of the back- and fore-arc stress states, magnitudes of slab suction flow under the subducting plates and mantle wedge flow under the overriding plates, and intraslab stress state in the subducting plate. The latter from the focal mechanism has been discussed in previous studies (Alpert et al., 2010 ; Bailey et al., 2012 ; Goes et al., 2017 ; Isacks and Molnar, 1971 ). The categories in Figs. 4 c and 4 d are similar to those in Figs. 6b and 6a of Conrad et al. ( 2004 ), respectively, but are slightly different, for example, the back-arc in the Japan Trench shows a compressional stress state, whereas that in the Aleutian Trench has a neutral stress state; the back-arc stress in Fig. 4 d is indicated by “C ~ N”. LSIEs are expected to occur in the subduction zone systems of categories I and II and not to (or to hardly) occur in those of categories III and IV. In category III (Fig. 4 c), a magnitude-9 mega-trench earthquake has not occurred in the Izu–Bonin (Ogasawara)–Mariana and Tonga Trenches since at least 1700 CE (McCaffrey, 2008 ). The intraslab stress is related to the morphology of the subducting plate in the mantle. According to the seismic tomography model focused on the Cascadia Trench (e.g., Hawley et al., 2016 ; Obrebski et al., 2010 ), the Mexico and Costa Rica Trenches (e.g., Li et al., 2008 ), and the Nankai Trough (e.g., Huang et al., 2013 ), high seismic velocity regions in the shallower lower mantle—indicating the morphology of the subducting plate—do not directly reach the highly viscous lower mantle and are not subject to resistance forces from the lower mantle, which generates DDT in the shallower part of the subducting plate. LSIEs seem to occur frequently in these trenches (Table 1 ). An LSIE occurred near the southernmost part of the Sumatra Trench in 2000. High-resolution seismic tomography demonstrated that the subducting Indian Plate penetrates the shallower lower mantle at a depth of approximately 1,000 km (Li et al., 2008 ; Zahirovic et al., 2014 ) and does not appear to stagnate in the mantle transition zone, which is consistent with the fact that the intraslab stress shows DDT because the slab is not subjected to resistance forces from the lower mantle. Therefore, the dynamic condition in the southernmost part of the Sumatra Trench was classified as Category I in this paper (Fig. 4 a). On the other hand, in 2004, a megathrust earthquake occurred in the Andaman Trench, ( M w 9.3 Sumatra Earthquake), and an LSIE seemed to occur (Table 1 ). This trench shows back-arc spreading in the Andaman Sea (Diehl et al., 2013 ). High-resolution seismic tomography images showed that the subducting Indian Plate penetrated the lower mantle at a depth of approximately 1,000 km (Li et al., 2008 ; Zahirovic et al., 2014 ), which is consistent with the fact that the intraslab stress showed DDT. Because the largest part of the Andaman Trench has fore- and back-arc extension (Fig. 3 d), the Andaman Trench was grouped into Category II in this study (Fig. 4 b). For the Japan Trench, a magnitude-9 class megathrust earthquake should not occur from a classical “comparative subductology” perspective (Uyeda and Kanamori, 1979 ), but in 2011 a M w 9.0 earthquake occurred off the Pacific coast of Tohoku. An LSIE has not been confirmed in the Japan Trench in recorded history. Therefore, this trench was grouped into Category IV (Fig. 4 d). Following this categorization, an LSIE should not occur in the Japan Trench where moderate lateral mantle flow is expected due to the formation of the stagnant slab with a lateral width of over 1,000 km around the base of the mantle transition zone (e.g., Zhao, 2015 ). Figure 5 shows the result of a three-dimensional numerical simulation of mantle convection with plate subduction based on a model of Yoshida ( 2013 ) and Tajima et al. ( 2015 ), whose dynamic situation is assumed to be the Japan Trench. Strong slab suction flow under the subducting plate and strong lateral mantle flow in the mantle wedge are generated because the subducting plate stagnates around the base of the mantle transition zone. Furthermore, the calculated surface stress state shows fore- and back-arc compression. This dynamic situation was grouped into Category IV (Fig. 4 d). Discussion In this study, I evaluated dynamic conditions for LSIEs using a dataset for the intraslab stress state, stress state of the overriding plate, motion speed of the overriding and subducting plates, and trench migration speed using geodetic data of plate motion in contrast to the qualitative evaluation based on seismological and geological observations of trenches by Seno and Yoshida ( 2004 ). LSIEs occur in the Cascadia, Mexico, and Costa Rica Trenches as well as the Nankai Trough relatively often. Seno and Yoshida ( 2004 ) suggested that LSIEs occur in trench regions where the overriding plate shows a lateral stress gradient, and the Kuril, Manila, and Sumatra Trenches were considered exceptions. The present study suggests that these trenches have compressional stress states in the fore-arc and nearly-neutral stress state in the back-arc, and were grouped into Category I in this paper (Fig. 4 a). Neither magnitude-9 megathrust earthquakes nor LSIEs have occurred in the Izu–Bonin (Ogasawara) and Tonga Trenches in recorded history. On the other hand, LSIEs have been confirmed near Gaum Island off the Mariana Trench (Table 1 ). In addition, Harada and Ishibashi ( 2008 ) reported that three earthquakes near Gaum Island on August 8, 1993 (depth = 67 km, M w 7.8), October 12, 2001 (depth = 62 km, M w 7.0), and April 26, 2002 (depth = 69 km, M w 7.1) were taken as intraslab earthquakes, which occurred in the subducting Pacific Plate, and not as interplate earthquakes. Although the focal mechanisms of these three earthquakes showed DDT, even though the epicenter depths were slightly deeper than 60 km, the dynamic environments of these earthquakes can be explained by Category II (in Fig. 4 b). The difference between the Izu–Bonin (Ogasawara) and Mariana Trenches was attributed to the behavior of the subducting plate. The former trench stagnates at the base of the mantle transition zone, whereas the latter penetrates the 660 km phase boundary (e.g., Fukao and Obayashi, 2013 ; Fukao et al., 2001 ). Thus, down-dip compression (DDC) appears in the slab under the Izu–Bonin (Ogasawara) Trench, whereas both DDT and DDC appear in the shallower and deeper parts of slabs in the Mariana Trench (Goes et al., 2017 ). In other words, it may be concluded that the morphology of the subducting plate in the mantle transition zone affects the possibility of an LSIE occurring. The Java and Kermadec Trenches, where neither megathrust earthquakes (McCaffrey, 2008 ) nor LSIEs have occurred in recorded history, have DDT in the shallower parts of the slabs (Alpert et al., 2010 ; Bailey et al., 2012 ; Goes et al., 2017 ; Isacks and Molnar, 1971 ), and the focal mechanisms show a neutral back-arc in the Java Trench and back-arc extension in the Kermadec Trench (Lallemand et al., 2008 ). Therefore, these two trenches may be grouped into Category III (Fig. 4 c). The complex behavior of mantle flow under the overriding and subducting plates depends on the morphology of the subducting plate and trench morphology, amongst others. However, the stagnant slab around the base of the mantle transition zone can generate strong lateral flow in the mantle wedge, and the penetration of the subducting plate can generate slab suction flow under the subducting plate. Three-dimensional numerical simulations of mantle convection considering plate subduction may help to resolve these problems regarding deep mantle flow and the effects of mantle flow on the stress states in the subducting slab and overriding plate, but it is nevertheless difficult to simulate subduction dynamics in individual trenches even with modern computational power. For example, the high-resolution numerical model focused on the Japan Trench (Fig. 5 ), the surrounding tectonics of which are relatively simple, has a numerical resolution of ~ 8 km and ~ 9 km in the vertical and horizontal directions, respectively, which are insufficient for treating complex surface tectonics. Nonetheless, LSIEs can be key to a deeper understanding of the relationship between the surface observation and underlying mantle flow from the perspective of slab-plate coupling and interplate coupling and are a unique type of earthquake that can be used to discuss a solid-earth system, linking seismology and mantle dynamics. Declarations Acknowledgements Some figures were produced by using Generic Mapping Tools software (Wessel et al., 2013). Author contributions M.Y. performed all the analyses and wrote the manuscript. Funding The author received no financial support for the research, authorship, and/or publication of this article. 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Int. 141(3):183-206. https://doi.org/10.1016/j-pepi.2003.11.002. Steinberger B, Sutherland R, O'Connell RJ (2004) Prediction of Emperor-Hawaii seamount locations from a revised model of global plate motion and mantle flow. Nature 430:167-173. https://doi.org/10.1038/nature02660. Tajima F, Yoshida M, Ohtani E (2015) Conjecture with water and rheological control for subducting slab in the mantle transition zone. Geosci. Front. 6(1):79-93. https://doi.org/10.1016/j.gsf.2013.12.005. Utsu T (1972) Large earthquakes near Hokkaido and the expectancy of the occurrence of a large earthquake off Nemuro. Rep. Coord. Comm. Earthq. Predict. 7:7-13 (in Japanese). Utsu T (1982) Tables of earthquakes with magnitude 6.0 or larger and earthquakes associated with damage near Japan: 1885–1980. Bull. Earthq. Res. Inst. 57:401–463. Uyeda S, Kanamori H (1979) Back-arc opening and the mode of subduction. J. Geophys. Res. 84(B3):1049-1061. https://doi.org/10.1029/JB084iB03p01049. Wessel P, Smith WHF, Scharroo R, Luis JF, Wobbe F (2013) Generic Mapping Tools: Improved version released. EOS Trans. AGU 94(45):409-410. https://doi.org/10.1002/2013EO450001. Wong IG (2005) Low potential for large intraslab earthquakes in the central Cascadia subduction zone Bull. Seismo. Soc. Am. 95(5):1880-1902. https://doi.org/10.1785/0120040132. Ye L, Lay T, Bai Y, Cheung KF, Kanamori H (2017) The 2017 M w 8.2 Chiapas, Mexico, Earthquake: Energetic Slab Detachment. Geophys. Res. Lett. 44(23):11824-11832. https://doi.org/10.1002/2017GL076085. Yoshida M (2013) The role of harzburgite layers in the morphology of subducting plates and the behavior of oceanic crustal layers. Geophys. Res. Lett. 40(20):5387-5392. https://doi.org/10.1002/2013GL057578. Yoshida M (2017) Trench dynamics: Effects of dynamically migrating trench on subducting slab morphology and characteristics of subduction zones systems. Phys. Earth Planet. Int. 268:35-53. https://doi.org/10.1016/j.pepi.2017.05.004. Zahirovic S, Seton M, Müller RD (2014) The Cretaceous and Cenozoic tectonic evolution of Southeast Asia. Solid Earth 5:227-273. https://doi.org/10.5194/se-5-227-2014. Zhao D (2015) Multiscale Seismic Tomography. Springer Japan, Tokyo, 304 pp. Additional Declarations No competing interests reported. Supplementary Files suppl240621clean.docx Cite Share Download PDF Status: Published Journal Publication published 09 Oct, 2024 Read the published version in Geoscience Letters → Version 1 posted Editorial decision: Revision requested 21 Sep, 2024 Reviews received at journal 16 Sep, 2024 Reviewers agreed at journal 04 Sep, 2024 Reviews received at journal 28 Jul, 2024 Reviewers agreed at journal 14 Jul, 2024 Reviewers invited by journal 14 Jul, 2024 Editor assigned by journal 08 Jul, 2024 Submission checks completed at journal 22 Jun, 2024 First submitted to journal 18 Jun, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4598015","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":326744480,"identity":"b5811231-49bb-4274-8ba5-a396c3526013","order_by":0,"name":"Masaki Yoshida","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABDklEQVRIiWNgGAWjYJACxgYDBjn2BiArAcoHkcyEtBjzHABpSSBaCwNDYg9IC9Qa/EC3/fjDjzMKDqf3sB9g+/DwR13i2vbmBoYfNQzs5ji0mJ3JMZbcYHA4t4cngXlGQsLhxG1nDjYw9hxjYLZswKHlQA6D5AOglv0SQNcnJBxI3HYjsYGBt4GB2eAADi3nnz/+CdSSzgPRUpe47f7DBsa/+LTcSDADOSwBqoUZaAtjAzNeW268MbOcYZBu2MOT2MyQkHbYeNuZxIbDMsckcPvlfPrjmz1/rOV52A8fZvxhUye77fjxhw/f1Ngk4woxKGhmgMUgGACdJJFsgF9LHaaQHQEto2AUjIJRMHIAAIJjYFnHY6k8AAAAAElFTkSuQmCC","orcid":"","institution":"Ritsumeikan University","correspondingAuthor":true,"prefix":"","firstName":"Masaki","middleName":"","lastName":"Yoshida","suffix":""}],"badges":[],"createdAt":"2024-06-18 07:14:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4598015/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4598015/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s40562-024-00361-7","type":"published","date":"2024-10-09T15:56:58+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":60276244,"identity":"d35a3dff-e8af-4643-83a5-203310939113","added_by":"auto","created_at":"2024-07-15 05:18:53","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1316686,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Distributions and focal mechanisms of the large shallow intraslab earthquakes listed in Table 1. (b) Close-up view around the Mexico and Costa-Rica Trenches shown by a small orange rectangle in (a). (c) Close-up view of a part of Washington, United States, shown by an orange rectangle in (a). Blue, green, and red lines indicate the trenches, transform-faults, and ridges, respectively.\u003c/p\u003e","description":"","filename":"Figure01300dpi.png","url":"https://assets-eu.researchsquare.com/files/rs-4598015/v1/4280c0f1952aaebe58e22347.png"},{"id":60276247,"identity":"e9f2a61d-6fda-476d-9074-a64b37ee6d91","added_by":"auto","created_at":"2024-07-15 05:18:53","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":76231,"visible":true,"origin":"","legend":"\u003cp\u003eDefinitions of the velocity of the overriding plate (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eup\u003c/em\u003e\u003c/sub\u003e), subducting plate (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003esub\u003c/em\u003e\u003c/sub\u003e), and speed of trench migration (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e) following the work of Lallemand et al. (2008). Negative and positive values of back-arc (\u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e) and fore-arc (\u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e) deformations show extension (i.e., spreading) and compression (i.e., shortening), respectively.\u0026nbsp;\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4598015/v1/725519bc0ab959db2fd87a0b.png"},{"id":60276246,"identity":"8222e835-8b3d-4057-9611-d3e6c712c4fd","added_by":"auto","created_at":"2024-07-15 05:18:53","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":649337,"visible":true,"origin":"","legend":"\u003cp\u003eDiagrams relating to trenches in HS3 reference frame (Gripp and Gordon, 2002). Velocities of the subducting plate (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003esub\u003c/em\u003e\u003c/sub\u003e) versus the that of overriding plate (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eup\u003c/em\u003e\u003c/sub\u003e) for (a) 166 trenches and (b) trenches where the large shallow intraslab earthquakes (LSIEs) occur. Back-arc deformation (\u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e) versus fore-arc deformation (\u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e) for (c) 166 trenches and (d) trenches where LSIEs occur. Green, gray, and orange circles show the extension, neutral, and compressional stress regimes in the back-arc as deduced from focal mechanisms of earthquakes following the work of Lallemand et al. (2008). Abbreviations in (d): SHEB#: southern New Hebrides Trench; NHEB#: northern New Hebrides Trench; ANDA#: Andaman Trench; SMAR#: southern Mariana Trench; LUZ#: Luzon (Manila) Trench; NCHI#: Northern Chile Trench; CASC#: Cascadia Trench (where “#” is the number indicating each transect across the trenches; see Table 1 of Lallemand et al. (2008)).\u003c/p\u003e","description":"","filename":"Figure03300dpi.png","url":"https://assets-eu.researchsquare.com/files/rs-4598015/v1/32244546f28b5a1930700468.png"},{"id":60276248,"identity":"bc921cd3-ba9a-45dd-ac25-caaaa6b19013","added_by":"auto","created_at":"2024-07-15 05:18:53","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1383498,"visible":true,"origin":"","legend":"\u003cp\u003eCategories showing the relationship between the intraslab and arc stress and the occurrence of large shallow intraslab earthquakes (LSIEs) and magnitude-9 class megathrust earthquakes. (a) Subducting slab shows down-dip tension (DDT) in the shallower part of the subducting slab and the arc shows broadly compressional field, e.g., the Sumatra, Kamchatka–Kuril, Peru, and Chile Trenches. (b) Subducting slab shows DDT and the arc shows a tensional-to-neutral field in the back-arc, e.g., the Alaska, Mariana, Cascadia, Mexico, and Costa Rica Trenches, as well as the Nankai Trough. (c) Subducting slab shows down-dip compression (DDC) and the arc shows broadly tensional-to-neutral stress field, e.g., the Izu–Bonin (Ogasawara) and Tonga Trenches. (d) Subducting slab shows neutral stress, and the arc shows compressional-to-neutral field in the back-arc, and compressional field in the fore-arc, e.g., the Japan and Aleutian Trenches. The outward-pointing arrows with abbreviation “T” indicate the extensional stress field, the inward-pointing arrows with abbreviation “C” indicate the compressional stress field, and the abbreviation “N” indicates the neutral stress state. LSIEs may occur in categories I and II, whereas it is unlikely to occur in categories III and IV.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4598015/v1/7ea4f22948bd4b421483248f.png"},{"id":60276628,"identity":"a51d4bca-0d53-4c51-8a65-32f262ae5bd0","added_by":"auto","created_at":"2024-07-15 05:26:53","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1392121,"visible":true,"origin":"","legend":"\u003cp\u003eSnapshots from the numerical simulation of mantle convection with slab subduction based on the model of Yoshida (2013) (For the model setup, see Yoshida (2013) and Tajima et al. (2015).). The upper color bar indicates the temperature in the model region, and the lower one indicates the surface stress (red and blue means compressional and extensional stress, respectively). The subducting plate stagnates around the base of the mantle transition zone. The model setup and the dynamics situation are similar to Category IV in Fig. 4d. The red and blue circles respectively show strong slab suction flow under the subducting plate and strong horizontal mantle flow in the mantle wedge under the overriding plate. The outward-pointing arrows marked “C” indicate the fore- and back-arc compression.\u003c/p\u003e","description":"","filename":"Figure05300dpi.png","url":"https://assets-eu.researchsquare.com/files/rs-4598015/v1/07d74e584ab227ee64dd73e9.png"},{"id":66597034,"identity":"b20dc19d-7243-481f-bd1b-d8d4b547059a","added_by":"auto","created_at":"2024-10-14 16:05:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5174151,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4598015/v1/ff27149e-f33c-48a0-b5df-e70f95a6425f.pdf"},{"id":60276249,"identity":"8c221216-19a2-4acc-93d5-d5824fbad389","added_by":"auto","created_at":"2024-07-15 05:18:53","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":493070,"visible":true,"origin":"","legend":"","description":"","filename":"suppl240621clean.docx","url":"https://assets-eu.researchsquare.com/files/rs-4598015/v1/b2e3fa1f85985e4f56c0cf6f.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Dynamic conditions for large shallow intraslab earthquakes","fulltext":[{"header":"Introduction","content":"\u003cp\u003eLarge shallow intraslab earthquakes (LSIEs) of over magnitude-7 rarely occur at depths of \u0026le;\u0026thinsp;60 km (Preston et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Seno and Yoshida, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). A \u003cem\u003eM\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e 8.2 intraslab earthquake occurred in Chiapas, Mexico, on September 8, 2017 (Ye et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), which caused severe damage. Since LSIEs cause severe damage owing to the shallower depths of their epicenters, deep understanding of the mechanism of LSIEs can aid hazard assessments in areas near related subduction zones. Furthermore, the occurrence of LSIEs possibly depends on dynamic interactions between not only the subducting and overriding plates but also between these plates and underlying mantle flow. Therefore, the study of the dynamic conditions for LSIEs is key to understanding the relationship between the Earth\u0026rsquo;s surface activity, which is directly observable, and the Earth\u0026rsquo;s deep activity, which is not directly observable and indirectly studied by, for example, numerical simulations, seismic tomography, and geochemical analyses of mantle rocks.\u003c/p\u003e \u003cp\u003eBased on the focal mechanisms of earthquakes, slab stress, and the stress state of overriding plates near the 20 events listed by the Global CMT catalog (Dziewonski et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1981\u003c/span\u003e; Ekstr\u0026ouml;m et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) and individual studies, Seno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) concluded that LSIEs occur in tectonic environments with down-dip tension (DDT) in the shallower part of the subducting plate and tensional back-arc stress, except for a few events. However, their analyses were based on a dataset from seismological and geological evidence and not on geodetic observation of plate motion, and they did not clearly discuss the phenomenon in terms of the relationship between surface observation and underlying mantle dynamics.\u003c/p\u003e \u003cp\u003eGeodetic information of plate motion is useful for estimating not only absolute velocity and motion but also the deformation rate of the plate interior near a trench. In particular, such geodetic information produces a quantitative estimation of the stress state of the subducting and overlying plates and complements information from geological observations and focal mechanisms (e.g., Lallemand et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Lallemand et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). In this study, I investigated dynamic conditions for LSIEs using a dataset for the intraslab stress state, stress state of the overriding plate, motion speed of the overriding and subducting plates, and trench migration speed (i.e., trench advance or retreat) determined by geodesic observation.\u003c/p\u003e \u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003eDynamic conditions for large shallow intraslab earthquakes\u003c/h2\u003e \u003cp\u003eSeno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) studied events with depths of 20\u0026ndash;60 km, because events at depths shallower than 20 km cannot be distinguished from outer-rise events, and those deeper than 60 km are caused by unbending processes in the elastic core of the plate (Engdahl and Scholz, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1977\u003c/span\u003e) and thermal stress constrained by slab morphology (Hamaguchi et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1977\u003c/span\u003e). Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e is a modified list of LSIEs based on the study by Seno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) and updated information. This list was constructed mostly from the studies by Preston et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2002\u003c/span\u003e) and Wong (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) for the Cascadia Trench, Ye et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) for the Mexico Trench, Mallick et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) for the Sumatra\u0026ndash;Andaman Trench, and Harada and Ishibashi (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) for the Mariana Trench, in addition to information from the Global CMT catalog and other individual studies.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eList of large shallow intraslab earthquakes.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"13\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNo.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eEvent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTrench\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eOrigin (year/month/day)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eEpicenter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eM\u003c/em\u003e\u003csub\u003e\u003cem\u003eW\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003ed\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c11\" namest=\"c9\"\u003e \u003cp\u003eFaulting parameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSlab age\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eReferences\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLat.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLon.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cem\u003eϕ\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cem\u003eδ\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cem\u003eλ\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSumatra\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSumatra\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2000/06/04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;4.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e101.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e152\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e60\u0026ndash;72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eSeno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSumatra\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAndaman\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2010/06/12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e91.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e115\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e149\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e69\u0026ndash;86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eMallick et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2017\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eManila\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLuzon (Manila)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1999/12/11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e15.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e119.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e112\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;169\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e18\u0026ndash;32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eSeno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKii-Yamato\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003eNankai\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1899/03/07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e34.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e136.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003e17\u0026ndash;21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eUtsu (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1982\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGeiyo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2001/03/24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e34.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e132.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e6.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e181\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003ePreston et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2002\u003c/span\u003e); Seno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGeiyo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1905/01/02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e34.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e132.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eUtsu (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1982\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYoshino\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1952/07/18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e34.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e135.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e6.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eUtsu (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1982\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHyuganda\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1931/11/02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e32.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e132.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eUtsu (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1982\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGuam\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMariana\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1993/08/08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e12.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e144.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e238\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e156\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eHarada and Ishibashi (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2008\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHokkaido-Toho-Oki\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eKuril\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1994/10/04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e43.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e146.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e8.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e158\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e118\u0026ndash;128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eUtsu (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1982\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEtorofu-Oki\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1958/11/07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e44.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e148.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e8.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eHarada and Ishibashi (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2000\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKodiak Is.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eW. and E. Alaska\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1999/12/06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e57.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;154.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e357\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e40\u0026ndash;52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eUtsu (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1982\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNisqually\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eCascadia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2001/02/28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e47.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;122.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e6.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e176\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e10\u0026ndash;11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003ePreston et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2002\u003c/span\u003e); Wong (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2005\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSeattle-Tacoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1965/04/29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e47.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;122.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e6.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e344\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003ePreston et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2002\u003c/span\u003e); Wong (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2005\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOlympia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1949/04/13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e47.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;122.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;135\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eBaker and Langston (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1987\u003c/span\u003e); Preston et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2002\u003c/span\u003e); Wong (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2005\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChiapas\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eMexico\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2017/09/08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e15.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-94.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e8.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e148\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e-83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003e8\u0026ndash;15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eYe et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOaxaca\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1999/09/30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e15.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;96.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;103\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eYe et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOaxaca\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1931/01/15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e16.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;96.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eYe et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOaxaca\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1907/04/15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e16.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;97.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eYe et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), USGS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMichoac\u0026aacute;n\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1997/01/11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e18.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;102.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e175\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eSeno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGuerrero\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1957/07/28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e17.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;99.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eYe et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), USGS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEl Salvador\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCosta-Rica\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1982/06/19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e12.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;88.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;106\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e22\u0026ndash;28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eSeno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEl Salvador\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2001/01/13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e12.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;89.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e121\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003ePreston et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2002\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePeru\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePeru\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1970/05/31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;9.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;78.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e160\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e31\u0026ndash;46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eAbe (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1972\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTaltal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN. Chile\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1965/02/23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;25.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;70.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e52\u0026ndash;53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eUtsu (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1982\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVanuatu\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eS. and. N. New Hebrides\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1994/07/13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;16.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e167.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e272\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e45\u0026ndash;60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eUtsu (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1982\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVanuatu\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1981/07/06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;22.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e170.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e345\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;179\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eUtsu (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1982\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"13\"\u003eSymbols: \u003cem\u003ed\u003c/em\u003e: depth; \u003cem\u003eδ\u003c/em\u003e: dip; \u003cem\u003eλ\u003c/em\u003e: rake; \u003cem\u003eϕ\u003c/em\u003e: strike. Abbreviations: USGS: United States Geological Survey webpage: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://earthquake.usgs.gov/earthquakes/\u003c/span\u003e\u003cspan address=\"https://earthquake.usgs.gov/earthquakes/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe largest LSIEs were the 1994 Hokkaido\u0026ndash;Toho\u0026ndash;Oki Earthquake and the 1958 Etrofu\u0026ndash;Oki Earthquake, which occurred in the Kuril Trench, with a magnitude of 8.3. Although the latter was considered to be an interplate earthquake (Utsu, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e1972\u003c/span\u003e), more recent seismic analyses have suggested that this was an intraslab earthquake (Harada and Ishibashi, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2000\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eLallemand et al. (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) presented the absolute velocity of the subducting plates, overriding plates, and trench migration (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003esub\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eup\u003c/em\u003e\u003c/sub\u003e, and \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e, respectively) on 166 transects at every 2\u0026deg; along subduction zones based on the three plate motion reference frames, i.e., HS3 (Gripp and Gordon, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2002\u003c/span\u003e), SB04 (Becker, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Steinberger et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2004\u003c/span\u003e), and NNR (DeMets et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Gripp and Gordon, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). In their definition, the relative value of back-arc deformation is defined by \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e \u0026equiv; \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e \u0026minus; \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eup\u003c/em\u003e\u003c/sub\u003e, where negative and positive \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e values indicate back-arc compression (i.e., shortening) and extension (i.e., spreading), respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). In this paper, the relative value of fore-arc deformation is defined by \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e \u0026equiv;\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003esub\u003c/em\u003e\u003c/sub\u003e \u0026minus; \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eup\u003c/em\u003e\u003c/sub\u003e, where negative and positive \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e values indicate fore-arc compression (i.e., shortening) and extension (i.e., spreading) respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo determine the relationship between the back- and fore-arc stress states, I plotted \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e-versus-\u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e diagrams of the 166 trenches in the three reference frames (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec and Figs. S1c and S2c in the supplementary material). On the other hand, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed and Figs. S1d and S2d in the supplementary material show the \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e-versus-\u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sub\u003e diagram of trenches where LSIEs occur; I identified 48 trenches relating to LSIEs, including the Sumatra, Andaman, Luzon (Manila), Mariana, Kuril, Alaska, Cascadia, Mexico, Costa Rica, Peru, Northern Chile, and New Hebrides Trenches as well as the Nankai Trough (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These 48 trenches include 13, 26, and 9 trenches of compressional, neutral, and extensional regimes in the back-arc, respectively, as deduced from research on the focal mechanisms of earthquakes (Lallemand et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Lallemand et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). It was found that the distribution of these plots did not depend on the reference frames, although the \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003esub\u003c/em\u003e\u003c/sub\u003e-versus-\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eup\u003c/em\u003e\u003c/sub\u003e diagrams (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and Figs. S1a and S2a in the supplementary material) and the \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003esub\u003c/em\u003e\u003c/sub\u003e-versus-\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e diagram (note that \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eup\u003c/em\u003e\u003c/sub\u003e ~ \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e in many trenches (Lallemand et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2008\u003c/span\u003e)) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb and Figs. S1b and S2b in the supplementary material) show variations in the three reference frames. Because the velocities of the subducting and overriding plates and the speed of trench migration in each trench depend on the reference frame (e.g., Heuret and Lallemand, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Schellart et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), it was difficult to quantitatively determine the effects of the relative plate motion of the subducting and overriding plates on the stress states of the back- and fore-arcs. Therefore, I focused only on the dynamic conditions for LSIEs in terms of the relationship between the back- and fore-arc stress states from the geodetic data and intraslab stress from the focal mechanisms.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed demonstrates that LSIEs are found for a wide range of \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e values, varying from \u0026minus;4.44 cm yr\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to +\u0026thinsp;2.06 cm yr\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and many trenches (29 of 48) are neutral, i.e., \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e = 0.0 cm yr\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. However, the 10 trenches with \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e \u0026lt; 0 are a part of the southern and northern New Hebrides, southern Mariana, and Andaman Trenches, which are minor compared to other trenches in the Western Pacific and northern Australian Plate off Indonesia. The five trenches with \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e \u0026gt; 0 are a part of the Luzon (Manila) and Northern Chile Trenches, which are relatively minor compared to other major trenches. Therefore, I concluded that LSIEs prefer tectonic conditions under (1) a nearly neutral stress state in the back-arc and (2) a compressional stress state in the fore-arc from the present analyses, and (3) DDT in the shallower part of the subducting plate, as previously suggested by Seno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eFour categories of subduction zones\u003c/h2\u003e \u003cp\u003eSubduction zone systems have geological, seismological, and geodynamic characteristics. For example, Conrad et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) classified trenches in subduction zone systems into two types in terms of the mechanical coupling between the surface and subducting plates. One type includes trenches under conditions with a strong mechanical coupling between these plates, such as the South Chile, Aleutian, and Japan, and Kuril\u0026ndash;Kamchatka Trenches (Fig.\u0026nbsp;6a of Conrad et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2004\u003c/span\u003e)). In this type of subduction zone system, the slab pull force is decoupled or weakly coupled with the surface plate, because the convergent continent\u0026ndash;ocean margin is considered to be mechanically damaged in the shallower part of the subducting slab. The other type includes trenches under conditions with a weak mechanical coupling between them, such as the Tonga\u0026ndash;Kermadec, Java\u0026ndash;Andaman, and Izu\u0026ndash;Bonin (Ogasawara)\u0026ndash;Mariana Trenches (Fig.\u0026nbsp;6b of Conrad et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2004\u003c/span\u003e)). In this type, the slab pull force is strongly coupled with the surface plate because there is no mechanical damage in the shallower part of subducting slab when the continental plate moves backward from the trench (see Yoshida (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) for details).\u003c/p\u003e \u003cp\u003eThe above classification is used in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e to demonstrate the proposed four categories of subduction zone systems in terms of the back- and fore-arc stress states, magnitudes of slab suction flow under the subducting plates and mantle wedge flow under the overriding plates, and intraslab stress state in the subducting plate. The latter from the focal mechanism has been discussed in previous studies (Alpert et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Bailey et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Goes et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Isacks and Molnar, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1971\u003c/span\u003e). The categories in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed are similar to those in Figs.\u0026nbsp;6b and 6a of Conrad et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2004\u003c/span\u003e), respectively, but are slightly different, for example, the back-arc in the Japan Trench shows a compressional stress state, whereas that in the Aleutian Trench has a neutral stress state; the back-arc stress in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed is indicated by \u0026ldquo;C\u0026thinsp;~\u0026thinsp;N\u0026rdquo;. LSIEs are expected to occur in the subduction zone systems of categories I and II and not to (or to hardly) occur in those of categories III and IV. In category III (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec), a magnitude-9 mega-trench earthquake has not occurred in the Izu\u0026ndash;Bonin (Ogasawara)\u0026ndash;Mariana and Tonga Trenches since at least 1700 CE (McCaffrey, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe intraslab stress is related to the morphology of the subducting plate in the mantle. According to the seismic tomography model focused on the Cascadia Trench (e.g., Hawley et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Obrebski et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), the Mexico and Costa Rica Trenches (e.g., Li et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), and the Nankai Trough (e.g., Huang et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), high seismic velocity regions in the shallower lower mantle\u0026mdash;indicating the morphology of the subducting plate\u0026mdash;do not directly reach the highly viscous lower mantle and are not subject to resistance forces from the lower mantle, which generates DDT in the shallower part of the subducting plate. LSIEs seem to occur frequently in these trenches (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAn LSIE occurred near the southernmost part of the Sumatra Trench in 2000. High-resolution seismic tomography demonstrated that the subducting Indian Plate penetrates the shallower lower mantle at a depth of approximately 1,000 km (Li et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Zahirovic et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) and does not appear to stagnate in the mantle transition zone, which is consistent with the fact that the intraslab stress shows DDT because the slab is not subjected to resistance forces from the lower mantle. Therefore, the dynamic condition in the southernmost part of the Sumatra Trench was classified as Category I in this paper (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003eOn the other hand, in 2004, a megathrust earthquake occurred in the Andaman Trench, (\u003cem\u003eM\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e 9.3 Sumatra Earthquake), and an LSIE seemed to occur (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). This trench shows back-arc spreading in the Andaman Sea (Diehl et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). High-resolution seismic tomography images showed that the subducting Indian Plate penetrated the lower mantle at a depth of approximately 1,000 km (Li et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Zahirovic et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), which is consistent with the fact that the intraslab stress showed DDT. Because the largest part of the Andaman Trench has fore- and back-arc extension (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed), the Andaman Trench was grouped into Category II in this study (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003eFor the Japan Trench, a magnitude-9 class megathrust earthquake should not occur from a classical \u0026ldquo;comparative subductology\u0026rdquo; perspective (Uyeda and Kanamori, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1979\u003c/span\u003e), but in 2011 a \u003cem\u003eM\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e 9.0 earthquake occurred off the Pacific coast of Tohoku. An LSIE has not been confirmed in the Japan Trench in recorded history. Therefore, this trench was grouped into Category IV (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). Following this categorization, an LSIE should not occur in the Japan Trench where moderate lateral mantle flow is expected due to the formation of the stagnant slab with a lateral width of over 1,000 km around the base of the mantle transition zone (e.g., Zhao, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the result of a three-dimensional numerical simulation of mantle convection with plate subduction based on a model of Yoshida (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) and Tajima et al. (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), whose dynamic situation is assumed to be the Japan Trench. Strong slab suction flow under the subducting plate and strong lateral mantle flow in the mantle wedge are generated because the subducting plate stagnates around the base of the mantle transition zone. Furthermore, the calculated surface stress state shows fore- and back-arc compression. This dynamic situation was grouped into Category IV (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, I evaluated dynamic conditions for LSIEs using a dataset for the intraslab stress state, stress state of the overriding plate, motion speed of the overriding and subducting plates, and trench migration speed using geodetic data of plate motion in contrast to the qualitative evaluation based on seismological and geological observations of trenches by Seno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). LSIEs occur in the Cascadia, Mexico, and Costa Rica Trenches as well as the Nankai Trough relatively often. Seno and Yoshida (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) suggested that LSIEs occur in trench regions where the overriding plate shows a lateral stress gradient, and the Kuril, Manila, and Sumatra Trenches were considered exceptions. The present study suggests that these trenches have compressional stress states in the fore-arc and nearly-neutral stress state in the back-arc, and were grouped into Category I in this paper (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003eNeither magnitude-9 megathrust earthquakes nor LSIEs have occurred in the Izu\u0026ndash;Bonin (Ogasawara) and Tonga Trenches in recorded history. On the other hand, LSIEs have been confirmed near Gaum Island off the Mariana Trench (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In addition, Harada and Ishibashi (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) reported that three earthquakes near Gaum Island on August 8, 1993 (depth\u0026thinsp;=\u0026thinsp;67 km, \u003cem\u003eM\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e 7.8), October 12, 2001 (depth\u0026thinsp;=\u0026thinsp;62 km, \u003cem\u003eM\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e 7.0), and April 26, 2002 (depth\u0026thinsp;=\u0026thinsp;69 km, \u003cem\u003eM\u003c/em\u003e\u003csub\u003e\u003cem\u003ew\u003c/em\u003e\u003c/sub\u003e 7.1) were taken as intraslab earthquakes, which occurred in the subducting Pacific Plate, and not as interplate earthquakes. Although the focal mechanisms of these three earthquakes showed DDT, even though the epicenter depths were slightly deeper than 60 km, the dynamic environments of these earthquakes can be explained by Category II (in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). The difference between the Izu\u0026ndash;Bonin (Ogasawara) and Mariana Trenches was attributed to the behavior of the subducting plate. The former trench stagnates at the base of the mantle transition zone, whereas the latter penetrates the 660 km phase boundary (e.g., Fukao and Obayashi, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Fukao et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Thus, down-dip compression (DDC) appears in the slab under the Izu\u0026ndash;Bonin (Ogasawara) Trench, whereas both DDT and DDC appear in the shallower and deeper parts of slabs in the Mariana Trench (Goes et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). In other words, it may be concluded that the morphology of the subducting plate in the mantle transition zone affects the possibility of an LSIE occurring.\u003c/p\u003e \u003cp\u003eThe Java and Kermadec Trenches, where neither megathrust earthquakes (McCaffrey, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) nor LSIEs have occurred in recorded history, have DDT in the shallower parts of the slabs (Alpert et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Bailey et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Goes et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Isacks and Molnar, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1971\u003c/span\u003e), and the focal mechanisms show a neutral back-arc in the Java Trench and back-arc extension in the Kermadec Trench (Lallemand et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Therefore, these two trenches may be grouped into Category III (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003eThe complex behavior of mantle flow under the overriding and subducting plates depends on the morphology of the subducting plate and trench morphology, amongst others. However, the stagnant slab around the base of the mantle transition zone can generate strong lateral flow in the mantle wedge, and the penetration of the subducting plate can generate slab suction flow under the subducting plate. Three-dimensional numerical simulations of mantle convection considering plate subduction may help to resolve these problems regarding deep mantle flow and the effects of mantle flow on the stress states in the subducting slab and overriding plate, but it is nevertheless difficult to simulate subduction dynamics in individual trenches even with modern computational power. For example, the high-resolution numerical model focused on the Japan Trench (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e), the surrounding tectonics of which are relatively simple, has a numerical resolution of ~\u0026thinsp;8 km and ~\u0026thinsp;9 km in the vertical and horizontal directions, respectively, which are insufficient for treating complex surface tectonics. Nonetheless, LSIEs can be key to a deeper understanding of the relationship between the surface observation and underlying mantle flow from the perspective of slab-plate coupling and interplate coupling and are a unique type of earthquake that can be used to discuss a solid-earth system, linking seismology and mantle dynamics.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSome figures were produced by using Generic Mapping Tools software (Wessel et al., 2013).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u0026nbsp;\u003c/strong\u003eM.Y. performed all the analyses and wrote the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u0026nbsp;\u003c/strong\u003eThe author received no financial support for the research, authorship, and/or publication of this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author declares that they have no competing interests\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbe K (1972) Mechanics and tectonic implications of the 1966 and 1970 Peru earthquakes. 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Springer Japan, Tokyo, 304 pp.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"geoscience-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"gosl","sideBox":"Learn more about [Geoscience Letters](https://geoscienceletters.springeropen.com/)","snPcode":"40562","submissionUrl":"https://submission.springernature.com/new-submission/40562/3","title":"Geoscience Letters","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4598015/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4598015/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLarge shallow intraslab earthquakes (LSIEs) of over magnitude-7 rarely occur at shallower depths (\u0026le;\u0026thinsp;60 km) in the subducting plates of the circum-Pacific and northern margin of the Australian Plate off Indonesia. Research has suggested that most LSIEs occur under surface tectonic conditions with a lateral stress gradient across the back-arc to the fore-arc on the overriding plate based on seismological and geological evidence from trenches. In this study, dynamic conditions for the occurrence of LSIEs were studied using the intraslab stress state, stress state of the overriding plate, motion speed of overriding and subducting plates, and trench migration speed determined by geodesic plate motion models. LSIEs prefer tectonic conditions under (1) a nearly neutral stress state in the back-arc, (2) a compressional stress state in the fore-arc, and (3) down-dip tension in the shallower part of the subducting plate. In particular, the trenches of major subduction zones where LSIEs occur have a neutral back-arc stress state as deduced from analyses of plate motion geodetic data. The results suggest that the Earth\u0026rsquo;s subduction zones can be classified into four categories. This categorization is informed by the behavior of underlying mantle flow, i.e., the magnitude of slab suction flow in the mantle under the subducting plates and the scale of return flow in the mantle wedge under the overriding plates, which varies the combination of stress states in the fore-arc, back-arc, and intraslab.\u003c/p\u003e","manuscriptTitle":"Dynamic conditions for large shallow intraslab earthquakes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-15 05:18:48","doi":"10.21203/rs.3.rs-4598015/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-09-22T01:56:00+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-09-16T08:34:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"308448852683267161771368401580426087152","date":"2024-09-05T01:23:33+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-28T08:31:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"8750518450753679756605725851013970893","date":"2024-07-15T03:58:38+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-07-14T13:51:10+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-07-09T02:18:15+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-06-22T12:43:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"Geoscience Letters","date":"2024-06-18T07:12:26+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"geoscience-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"gosl","sideBox":"Learn more about [Geoscience Letters](https://geoscienceletters.springeropen.com/)","snPcode":"40562","submissionUrl":"https://submission.springernature.com/new-submission/40562/3","title":"Geoscience Letters","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c136208d-d271-4961-a1cd-9fa1da6430f2","owner":[],"postedDate":"July 15th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-10-14T15:58:53+00:00","versionOfRecord":{"articleIdentity":"rs-4598015","link":"https://doi.org/10.1186/s40562-024-00361-7","journal":{"identity":"geoscience-letters","isVorOnly":false,"title":"Geoscience Letters"},"publishedOn":"2024-10-09 15:56:58","publishedOnDateReadable":"October 9th, 2024"},"versionCreatedAt":"2024-07-15 05:18:48","video":"","vorDoi":"10.1186/s40562-024-00361-7","vorDoiUrl":"https://doi.org/10.1186/s40562-024-00361-7","workflowStages":[]},"version":"v1","identity":"rs-4598015","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4598015","identity":"rs-4598015","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}