The 2022 M w 6.7 Menyuan earthquake: a cascade rupture reveals the high stress accumulation on the west section of Tianzhu seismic gap

The 2022 M w 6.7 Menyuan earthquake: a cascade rupture reveals the high stress accumulation on the west section of Tianzhu seismic gap | 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 The 2022 M w 6.7 Menyuan earthquake: a cascade rupture reveals the high stress accumulation on the west section of Tianzhu seismic gap Wei Chen, Wei Xiong, Bin Zhao, Yangmao Wen, Xuejun Qiao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4212637/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Aug, 2024 Read the published version in Pure and Applied Geophysics → Version 1 posted 9 You are reading this latest preprint version Abstract The January 8th 2022 menyuan earthquake(Mw6.7) occurred along major boundary fault zone in the northeastern Tibetan Plateau.In this study, we derived the co-seismic deformation from pixel offset tracking (POT) and interferometric synthetic aperture radar (InSAR) by using Sentinel-1 data. The inteferograms pattern shows that coseismic deformation is dominated by horizontal movements with the maximum displacement are over 0.5m in both tracks and POT results. Then we inverted the geometry parameters of the causactive fault and the slip distribution of the fault plane based on the finite dislocation model. The result shows the seismogenic fault has an average strike of 108.0 ◦ and a northeast dip angle of 83 ◦ . moreover, the coseismic slip is primarily concentrated on the lenglongling fault with on main asperity of 10 X 23 km and the maximum slip of 3.5m at depth of 4km as well as rupture the eastern of the tuolaishan fault with a small area of 5×5 km at depths of 0–8 km. On the basis of the dCFS results caused by historical earthquakes in tuolaishan fault and geodetic-derived slip rate of the tuolaishan fault, we emphasize the potential seismic risk on western Tianzhu gap is high. Menyuan earthquake Tianzhu seismic gap InSAR stress accumulation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction The left-lateral strike-slip Haiyuan fault system is a major boundary fault zone in the northeastern Tibetan Plateau, which is made by several segments including the Tuolai Shan fault (TLS F.), the Leng Long Ling fault (LLL F.), the Jin Qiang He fault (JQH F.), the Lao Hu Shan fault (LHS F.), the Mao Mao Shan fault (MMS F.), and the Haiyuan fault (HY F.) (Liu et al., 2007 ; Xiong et al., 2018; Fig. 1 ). Earthquakes occur frequently in the Haiyuan fault system and surrounding area, including two M w >7.5 events: the 1920 M w 7.8 Haiyuan earthquake and the 1927 M 7.9 Gulang earthquake, which produced 240 km and 140 km long surface rupture, respectively (Fig. 1 ). To the west of the 1920 Haiyuan earthquake lies the Tianzhu seismic gap, a 260-km-long fault zone, which has not experienced M w >7.0 earthquake in more than 800 years (Gaudemer et al. 1995 ; Jolivet et al., 2012 ). On January 8th, 2022, an M w 6.7 earthquake stuck the west segment of Tianzhu seismic gap, causing ~ 20-km-long surface rupture and significant ground deformation. The Lanzhou-Xinjiang high-speed railway, which passed through the causative fault, is forced to shutdown temporarily. The epicentre of the earthquake is located ∼50 km northwest of the city of Menyuan (USGS, 2022). Source mechanism solutions from teleseismic data (USGS, 2022; GCMT, 2022; Table 1) indicate that the 2022 Menyuan earthquake ruptured a steeply dipping strike-slip fault, which is consistent with the slip behaviour of the Haiyuan fault system. The distribution of the relocated aftershocks (Fan et al., 2022 ) confirms that the mainshock ruptured a bending section of the LLL fault, named Liuhuanggou segment, where the LLL fault intersects with the TLS fault. As the most lately strong event on the Tianzhu seismic gap, the 2022 Menyuan earthquake attracted a lot of attentions. Although the seismogenic fault locates in high altitude area with sparse GPS observations, the coseismic deformations associated with the 2022 Menyuan earthquake are recorded by spaceborne Interferometric Synthetic Aperture Radar (InSAR) and optical images. Consequently, the InSAR-derived coseismic deformation and the coseismic slip model (e.g., Li et al., 2022 ; Liu et al., 2022 ; Yang et al., 2022) are quickly presented. However, the coseismic deformation derived from offset tracking method has not been reported yet. Besides, the seismogenic environment of the earthquake and the potential seismic hazard on Tianzhu seismic gap after the earthquake need further investigation. In this study, we map the coseismic deformation fields of the Menyuan earthquake by the Sentinel-1 SAR interferograms.. Then, we perform simultaneous inversions for coseismic slip model using the InSAR and near-field pixel-offset data. Besides, we discuss about the interactions the 2022 earthquake and historical events, as well as the potential seismic hazard on western Tianzhu gap. 2. Data and Method 2.1. Geodetic observations In this study, we collected Synthetic Aperture Radar (SAR) data from the European Space Agency (ESA) Copernicus Sentinel-1A with Terrain Observation with Progressive Scan (TOPS) mode to measure the displacements caused by the 2022 Menyuan event. Fortunately, there are two ascending (T026A, T128A) and one Descending track (T033D) captured the deformation field caused by this event(Fig. 2 ). All SAR data were processed by GAMMA software (Werner and Wegmüller 2000) flowing the general DInSAR workflow. A 90 m Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) (Farr et al. 2000) was used to remove the effects of topography. To improve the signal-to-noise ratio of the interferogram, the interferogram in both the ascending and descending were then filtered with an adaptive power spectral filter (Goldstein and Werner 1998 ) to suppress phase noise. Because the deformation gradient is too high in near faults will cause the problem in phase unwrapping, we Masked low coherence areas in the interferogram with the coherence threshold is 0.3 before unwrapping.the differential phase is unwrapped using the minimum cost flow algorithm (MCF), and geocoding is performed to obtain the deformation in geographic coordinates. Due to the dry environmental condition in the study area, the interferometric phase in both the descending and ascending track look very clear and undisturbed. Fianlly we modeled residual orbital errors by applied a polynomial function and removed from the interferograms. As the the unwrapped phases were missing near the faults ,we use the pixel offset tracking(POT) method to detect the robust large deformation signals (Tobita et al. 2001 ; Kobayashi et al. 2009; Takada et al. 2009).The processing strategy refer to previous studies, we use the GAMMA software to do fine coregistration of SAR images before the POT analysis and then used autonomous repeat image feature tracking (autoRIFT) algorithm to calculate the POT deformation. we set the matching window size to 256x128 pixels for range and azimuth in order to improve POT accuracy.. There is a 3 m threshold was Selected to remove the Singularities with magnitude above the threshold (Yang et al. 2023 ). Finally the resultant offset maps was filtered by a Gaussian smoothing filter and geocoded in WGS84 coordinates. All three interferograms with high spatial resolution and good covrage in the study area result in millions of measure points ,leading to huge computation burdens.we used a A efficient and reliable quadtree down-sampling method to downsample the InSAR deformation field.We set the search mim windows size, max windows size and Segmentation threshold is 8, 256 and 0.1 respectively. Finally, For the cosesimic deformation, 778, 1030, 812, and 661 data points were retrieved from the T026A, T128A, T033D and T033D range offsettracking, respectively. For the post-seismic deformation, we get 1107 and 1076 data point for the T128A, T033D track, respectively. 2.2. Model configuration We inverted the co-seismic slip distribution of the 2022 menyuan mainshocks(Mw6.7) based on the descending and ascending observation data of Sentinel-1A. We adopted the steepest descend approach (SDM) algorithm based on the multi layered earth model ,which establishes a linear relationship between coseismic surface displacement and fault dislocation distribution after the fault geometry is determined(Wang et al., 2013 ). In order to get a smoothing slip model, it introduced a physical constraint to ensure the stability of the inversion that can be solved by a roughness term that is minimized in terms of data misft. a smooth stress drop is applied on the entire fault in our study. The aftershock refined sequences distribution is 23 Km in the NWW direction, which is generally consistent with the fault trace captured by the range offset-tracking result.The aftershocks were concentrated at depths of 4 to 12 km ( https://www.cea-igp.ac.cn/kydt/278812.html ). we constructed a rectangular fault plane with length and width were extended to 40 km along fault tract and 30 km following the down dip, respectively and the plane was divided into subpatches with sizes of 1km x 1km. According to the to the seismic geological data and the focal mechanism solution given by many institutions, the dip angle of the plane set a range from 60 o to 90 o . a grid search was applied to search for the optimal dip angle is 85 o , which realized through minimizing data misfit. As mentioned above, the smoothing factor is usually estimated by the trade-off curve between the stress roughness of the model and the ftting residuals.We chose the inflection point in the curve line as our appropriate smoothening factor is 0.06. All Green’s functions were calculated with the Crust 2.0 crustal model (Bassin et al.,2000). 3. Results 3.1 Co-seismic displacements The fringe patterns are Continuous and clear except for the decoherence area near the fault caused by high deformation gradient in both ascending and descending track. The fringe patterns in descending interferogram is almost completely symmetrical, covers a butterfly-shape while the number of fringes on both sides of the fault is similar in the ascending and descending orbit indicates that the seismogenic fault is strike-slipping fault with high dip angle. The LOS deformation were − 0.56 ~ 0.51m, -0.36 ~ 0.65m and − 0.30 ~ 0.68m for T033D,T128A and T026A track respectively(Fig. 2 ). In contrast to the LOS deformation accuracy, the offset maps accuracy is very limited and can only reach the decimeter level (Li et al., 2019 ). unfortunately, only the descending T033D Track in range offset map could capture the significant pixel-offset by as much as ~ 1m. It is important that the fault trace can be clearly observed from range offset maps, but is decorrelation caused by the surface ruptures in the LOS deformation map. In this study, the fault trace is used to constrain the fault model orientation. 3.2 Co-seismic slip As shown in Fig. 3 (d), The menyuan earthquake caused a surface rupture. The .The slip distribution is characterized by nearly purely left-lateral strike-slip with an average rake of 4.00◦ and an average slip of 0.13 m.The maximum slip is 3.5m at the depth of 4-5km and the seismic moment is about 1.8×10 19 N m (assuming a rigidity of 3.2×10 10 Pa),which is is equivalent to moment magnitude M W 6.7. As the observation and prediction correlation was 0.968, our model can sufficiently explain InSAR observations with RMS are 0.02m 0.02 and 0.01m for tracks T026A, T128A and T033D. The larger residuals with amplitude up to 4 ~ 5cm was mainly distributed nearby the fault trace in Fig. 3 (c). This RMS may primarily due to the simplified fault plane could not reproduce the high deformation gradients caused by the stepping geometry of real fault. 4. Discussion 4.1. A cascade rupture associated with the 2022 Menyuan earthquake The bulk of the coseismic slip associated with the 2022 Menyuan earthquake is located on LLL fault. The back-projected results suggest a relatively low rupture velocity (1.0-1.2 km/s) (Yang et al., 2022), which is consistent with the bending fault trace (Fig. 1 ), for the curved fault geometry is not conducive to the acceleration of fracture. The rupture involved not only the mapped fault trace, but also an unmapped ~ 6-km-long section which appears as a western extension of the Liuhuanggou segment (Fig. 4 ). The LLL fault, together with the TLS fault and Sunan-Qilian fault, form a brush structure, which convergent SE-wards and divergent NW-wards (Fig. 4 ). The brush structures are widely developed at the end of strike-slip faults, e.g. the Altyn Tagh fault (Li et al., 2020 ), and always present tensional property. The latter could explain the tensional cracks reported by field investigation (Han et al., 2022 ) and the normal-slip component in our coseismic slip model (Fig. 2 ). Although the slip on TLS fault is not as significant as that on LLL fault (Fig. 3 ), the surface rupture (Fig. 4 ) reveals that the eastern section of TLS fault is involved in the coseismic period, resulting a joint rupture associated with the 2022 Menyuan earthquake. Several large earthquakes with cascade rupture are reported near Haiyuan fault zone (e.g. the 1920 M w 7.9 Haiyuan earthquake, Ou et al., 2020 ; the 1927 M7.9 Gulang earthquake, Guo et al., 2020 ). However, the 2022 Menyuan earthquake provided a rare instance, in which an M w 6.7 earthquake induced a complex cascade rupture. It appears that the coseismic rupture did not propagate directly from the LLL fault to the TLS fault, for the ~ 3-km-long surface rupture gap on the TLS fault (Han et al., 2022 ) (Fig. 2 ). The surface rupture gap indicates a probably step-over locates between the LLL fault and TLS fault, which always acts as a barrier in the process of rupture propagation. The rupture on the TLS fault could be partly due to the stress transfer process (Stein, 1997), for the coseismic Coulomb stress change (dCFS) caused by the slip on LLL fault significantly raised the stress level on the region with surface rupture on the eastern TLS fault (Fig. 4 ). In addition, the surface rupture gap is covered by the stress shadow, in which the fault could be temporarily silenced by the stress release (Harris & Simpson, 1998). 4.2. Limited coseismic slip and high stress drop of the mainshock The 2022 M w 6.7 Menyuan earthquake produced a shallow coseismic rupture with peak slip of 3.15 m. Although it is infrequent for an M w 6.7 earthquake to produce ~ 20-km-long surface rupture, shallow ruptures are not uncommon on strike slip faults in the eastern margin of the Qinghai-Tibet Plateau. For instance, the rupture of the 2010 M w 6.8 Yushu earthquake concentrates in a depth range of 0–10 km (Wen et al., 2013 ). Similar shallow rupture is also found in the 2021 M w 7.4 Maduo earthquake (e.g. Zhao et al., 2021 ). The phenomenon is probably attributed to the thin sedimentary cover, whose thickness is 0 ~ 0.5 km in the eastern margin of the Qinghai-Tibet Plateau (Laske et al., 2013 ), for the sediments commonly present “weak” frictional property and behave as barriers for dynamic ruptures (Gabriel et al., 2012 ; Yue et al., 2021 ). However, the rupture dimensions and the magnitude of the coseismic slip associated with the 2022 event are worth mentioning. The bulk of the rupture (with slip larger than 0.5 m) concentrates in a 23 km × 10 km area, which is much smaller than the rupture area predicted by the empirical relationship from Wells & Coppersmith ( 1994 ). The latter suggests a rupture size of 38.4 km × 12 km. Moreover, the value of the peak slip (3.15 m), which is much larger than the predicted value of ∼0.7 m (Wells & Coppersmith, 1994 ), is probably the largest documented coseismic slip induced by M w < 7 events in Chinese mainland. The characteristics of the coseismic slip are comparable with that in the 2016 M w 6.2 Tottori, Japan earthquake (Ross et al., 2018 ) and the 2020 M w 6.4 Petrinja, Croatia earthquake (Xiong et al., 2022 ). The latter ruptured a ~ 45 km 2 patch with a peak slip of 3.5 m. The 2022 Menyuan earthquake occurred on the west end of the bending LLL fault. The causative fault intersects with the Lenglongling North fault on ~ 101.35°E, which is near the eastern end of the surface rupture (Fig. 4 ). The limited length and complex geometry of the causative fault is ideal to confine the rupture propagation, and thus yielding high coseismic slip on a small fault plane (Wang et al., 2017 ). Large coseismic slip limited within a small area always leads to large stress drop on the fault plane (Ross et al., 2017 , 2018 ; Zielke et al., 2017 ; Xiong et al., 2022 ). The stress drop of the 2022 Menyuan earthquake is estimated using the method of Stein & Wysession ( 2003 ). The maximum stress drop is approximately 14 MPa, which is much larger than the empirical values of ∼5 MPa for large earthquakes or 1–2 MPa for moderate earthquakes (Zielke & Arrowsmith 2008 ). The estimated stress accumulation rate on LLL fault is ~ 1.2 MPa/100 year (Li et al., 2017 ). The stress drop of the 2022 earthquake is equivalent to ~ 1100 years of tectonic loading. The large stress drop highlights the high stress accumulation on the west section of the Tianzhu seismic gap, which has not experienced strong earthquakes for centuries. 4.3. Stress transfer and potential seismic hazard on western Tianzhu seismic gap The seismic hazard on Tianzhu seismic gap is widely concerned, although part of the fault (e.g. the eastern segment of the LLL fault) is probably ruptured during the 1927 M7.9 Gulang earthquake (Guo et al., 2020 ). Previous studies suggested that the seismic risk on western Tianzhu seismic gap is higher than the eastern part, for the stress shadow on the latter caused by historical earthquakes (e.g. Xiong et al., 2019 ) and shallow aseismic creep on the LHS fault (e.g. Jolivet et al., 2012 ; Huang et al., 2022 ). This conclusion is partly proved by the occurrence of the 2022 Menyuan earthquake, which caused a joint rupture on western LLL fault and the TLS fault. Here, we present a further discussion about the potential seismic hazard on western Tianzhu seismic gap with stress transfer theory (Stein, 1997) and GPS-derived velocity field (Wang & Shen, 2020 ). Stress transfer theory has been widely used to assess the seismic risk on active faults (e.g. Freed, 2005 ; Stein, 2003 ). Subsequent earthquakes always occur in the stress loading area caused by historical earthquakes, and the faults located in stress shadow would be silenced by the stress release (e.g. Stein et al., 1997 ; McCloskey et al., 2005 ). Before the occurrence of the 2022 Menyuan earthquake, the dCFS caused by historical earthquakes produced a ~ 80-km-long stress loading area on the western Tianzhu gap, in which the dCFS is larger than 0.1 MPa (Fig. 5 a). Unsurprisingly, the 2022 Menyuan earthquake is occurred in the stress loading area, with a dCFS value of ~ 0.17 MPa on the epicentre (Fig. 5 c), corresponding to ~ 14 years of tectonic loading. The results are stable in different simulations with variable parameters (e.g. effective friction coefficient, viscosity coefficient), indicating that the occurrence of the 2022 event is probably promoted by the historical earthquakes. More importantly, the rupture of the 2022 event did not fill the stress loading area on the western Tianzhu gap, and the coseismic dCFS caused by the 2022 event has further enhanced the stress level on the eastern TLS fault, resulting a ~ 40-km-long segment with stress loading larger than 0.1 MPa (Fig. 5 b; Fig. 6 ). The potential seismic hazard on western Tianzhu gap is not only evidenced by dCFS results, but also by geodetic-derived slip rate and interseismic coupling on the fault plane. Based on the newly GPS-derived velocity field (Wang & Shen, 2020 ), we present a simple 2D model (Savage & Burford, 1973 ) to obtain the sinistral slip rate and interseismic coupling on the eastern TLS fault (Fig. 6 c). The statistical distribution of the slip rate and locking depth inferred from 500 Monte Carlo simulations (Fig. 6 d). The dislocation model suggests that the slip rate on the fault is 6.99 ± 0.46 mm/a, but with a locking depth of 72.2 ± 12.3 km, which is much deeper than the seismogenic thickness in this region (~ 20 km; Laske et al., 2013 ). The result indicates that the fault plane may be fully locked to the base of the seismogenic zone. In the context, we fixed the locking depth at 20 km, and the constrained model suggests a slip rate of 5.37 ± 0.14 mm/a (Fig. 6 d), which is comparable with the results of Li et al. ( 2017 ) and Huang et al. ( 2022 ). The fully locked fault plane is one of the key characteristics in the late period of earthquake cycle, and thus highlights the potential seismic risk on the western Tianzhu gap. 5. Conclusions In this study we described the co-seismic deformation caused by the 2022 Menyuan earthquake using Sentinel-1A observations. We used offset-pixel tracking deformation to obtain the fault trace and use Interferograms to constrain the deformation pattern. On the basis of InSAR observations, a finite dislocation model was implemented to invert the geometrical parameters of the causative fault and the slip distribution of the fault plane. Our inversion results show that the seismogenic fault rupture was dominated by strike-slip and was primarily on the LLL fault with one main asperity was concentrated at depths of 0–10 km covered 23 X 10 km2 as well as the TLS fault with a small size of 5×5 km2 at depths of 0–8 km. Although the 2022 menyuan earthquake cause the large stress drop on the west section of the Tianzhu seismic gap where is the high stress accumulation, we still highlight the potential seismic risk on western Tianzhu gap is high according to the dCFS results caused by historical earthquakes in TLS fault and geodetic-derived slip rate and interseismic coupling on the fault plane. Declarations Author Contribution Chen. Wei and Xiong. 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Earth and Planetary Science Letters , 570: 117066. Zhao, D., Qu, C., Chen, H., et al. (2021). Tectonic and geometric control on fault kinematics of the 2021 Mw7. 3 Maduo (China) earthquake inferred from interseismic, coseismic, and postseismic InSAR observations. Geophysical Research Letters , 48(18): e2021GL095417. Zielke, O., Galis, M., Mai, P. M. (2017), Fault roughness and strength heterogeneity control earthquake size and stress drop. Geophys. Res. Lett ., 44, 777–783. Zielke, O., Arrowsmith, J. R. (2008). Depth variation of coseismic stress drop explains bimodal earthquake magnitude‐frequency distribution. Geophysical Research Letters , 35(24). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 01 Aug, 2024 Read the published version in Pure and Applied Geophysics → Version 1 posted Editorial decision: Revision requested 27 May, 2024 Reviews received at journal 24 May, 2024 Reviews received at journal 13 May, 2024 Reviewers agreed at journal 06 May, 2024 Reviewers agreed at journal 22 Apr, 2024 Reviewers invited by journal 08 Apr, 2024 Editor assigned by journal 05 Apr, 2024 Submission checks completed at journal 05 Apr, 2024 First submitted to journal 03 Apr, 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. We do this by developing innovative software and high quality services for the global research community. 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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-4212637","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":288845353,"identity":"1d6af1b0-e154-4be2-a40f-39f03597d8c7","order_by":0,"name":"Wei Chen","email":"","orcid":"","institution":"CEA","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Chen","suffix":""},{"id":288845357,"identity":"646a9ba1-1de2-4d9d-9afc-586cd876c3f9","order_by":1,"name":"Wei Xiong","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABFklEQVRIie2RsWrDMBCGz6jIi6gzWqT1GxQuCDIF51VqDM6abt3aEFCXQNc8RqDg2cGQLIWuCVmiN3CHQobS9ESmQmUyFqpvkAbdx91/AvB4/iLsdAlgbLlvcJBE4WRimrOUkOe9+bhQclZPVXxWu0j0u6Kps8VmpDuipRDXbGU+9OAKmFC9ObJgsTUaYkiTm8ffFTnlI3WtC8rC7ygLZ3KX6f0YctWvHOMwmkeWtY3/Ql0Ev9xlTxhDlZUOhZ+UIylAWTAWsF1qOt2K7SLfy4qUC6tg3NkE7QplKbrBV26z0JLxFuUsoyWjOwu+1St5eE2HENX0lZ/Hh+dwbUxznyYuxcLsLwx/FqC73BIc2t89Ho/nv/MN5JFWKNh0gE8AAAAASUVORK5CYII=","orcid":"","institution":"CEA","correspondingAuthor":true,"prefix":"","firstName":"Wei","middleName":"","lastName":"Xiong","suffix":""},{"id":288845359,"identity":"47421c78-6983-4415-a63b-11210d65b99c","order_by":2,"name":"Bin Zhao","email":"","orcid":"","institution":"CEA","correspondingAuthor":false,"prefix":"","firstName":"Bin","middleName":"","lastName":"Zhao","suffix":""},{"id":288845360,"identity":"0d1944bf-4be9-4721-80dd-73f92b283816","order_by":3,"name":"Yangmao Wen","email":"","orcid":"","institution":"Wuhan University","correspondingAuthor":false,"prefix":"","firstName":"Yangmao","middleName":"","lastName":"Wen","suffix":""},{"id":288845361,"identity":"7d665378-2bd1-4879-bf36-4b926a4c9ad2","order_by":4,"name":"Xuejun Qiao","email":"","orcid":"","institution":"CEA","correspondingAuthor":false,"prefix":"","firstName":"Xuejun","middleName":"","lastName":"Qiao","suffix":""}],"badges":[],"createdAt":"2024-04-03 12:14:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4212637/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4212637/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00024-024-03544-7","type":"published","date":"2024-08-01T15:58:21+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":54405508,"identity":"c3b327df-3677-4f22-8abc-aae268498ece","added_by":"auto","created_at":"2024-04-10 03:48:42","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1147338,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003etectonic setting of study area. (\u003c/strong\u003ea)Geological map showing active faults in the northeastern Tibetan Plateau. The location of the menyuan earthquake(red beach ball) and Strong historical earthquakes (blue beach balls)are shown, as well as the locations of regional faults (black lines). Green bolded line indicate the several segaments of Haiyuan fault system. The dashed solid lines indicate the GPS profile along the Haiyuan fault. (b) the tectonics of the Haiyuan Fault system of study area. Black bolded line indicate the Haiyuan Fault system. Black and white stripes indicate the High-speed railway.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4212637/v1/ac665155f26e3c221f15665d.png"},{"id":54405505,"identity":"0fb88a0b-7fcf-491f-9197-99b2a14db751","added_by":"auto","created_at":"2024-04-10 03:48:42","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":604743,"visible":true,"origin":"","legend":"\u003cp\u003eSAR geodetic observations derived from Sentinel images used in this study. Panels (a,d) represent interfering phase and LOS deformation of ascending track T026; panels (b,e) represent interfering phase and LOS deformation of ascending track T128; panels (e,f) represent interfering phase and LOS deformation of descending track T033. panels (g) represent the range offset deformation of descending track T033. Nothe that the bolded black line indicate the fault trace identified in this study by the range offset.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4212637/v1/643863873564960272898b06.png"},{"id":54405787,"identity":"87a9e3d2-e7c7-4100-a46e-62ab4830fda3","added_by":"auto","created_at":"2024-04-10 03:56:42","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":559460,"visible":true,"origin":"","legend":"\u003cp\u003eThe slip distribution model and comparison of observed and synthetic and residual displacements of the 2022 menyuan earthquake based on the slip distribution model. (a1-a4) The observed displacements ,(b1-b4) the synthetic displacements and (c1-c4)the residuals displacements between the observed and synthetic displacements. (d)and(e) show the slip distribution of 2022 menyuan earthquake in this study.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4212637/v1/d04177d0ef78001b9b9a39b7.png"},{"id":54405788,"identity":"5aad635a-8c09-4e87-af2b-c9e92adce6e2","added_by":"auto","created_at":"2024-04-10 03:56:42","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":650025,"visible":true,"origin":"","legend":"\u003cp\u003e(a)the surface rupture caused by 2022 menyuan earthquake marked with bold black line.（b） Co-seismic Coulomb failure stress changes near the epicentre region of 2022 menyuan earthquakeat a depth of 10 km\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4212637/v1/1b8b19555f738cd812813ff0.png"},{"id":54405506,"identity":"b66b7d5e-f7bc-4208-90f5-9d9b5ad939b3","added_by":"auto","created_at":"2024-04-10 03:48:42","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":437833,"visible":true,"origin":"","legend":"\u003cp\u003e(a)The Coulomb failure stress changes caused by historical earthquakes in the TLS fault region.（b）Coseismic dCFS caused by the 2022 event in the TLS fault region. (c) Coseismic dCFS caused by historical earthquakes in the TLS fault region results for different friction coefficients.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4212637/v1/381621824e5b67b5b2111e55.png"},{"id":54405511,"identity":"969881ba-1f46-42e3-87df-744511fe596b","added_by":"auto","created_at":"2024-04-10 03:48:42","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":328454,"visible":true,"origin":"","legend":"\u003cp\u003eThe sinistral slip rate and interseismic coupling on the eastern TLS fault based on 2D model (a) The interseismic coupling on the fault plane on the nearby Faults. (b)The locking depth (c)The sinistral slip rate on the eastern TLS fault based on GPS-derived velocity field (Wang \u0026amp; Shen, 2020) . (d)The statistical distribution of the slip rate according to our constrained model.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4212637/v1/2d51247223eef338a36aa03a.png"},{"id":61794077,"identity":"288b31b4-ac8e-463a-bb07-93a04b360d21","added_by":"auto","created_at":"2024-08-05 16:17:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4279449,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4212637/v1/f605accd-9976-47fe-9af1-96b43c60bc1a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The 2022 M w 6.7 Menyuan earthquake: a cascade rupture reveals the high stress accumulation on the west section of Tianzhu seismic gap","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe left-lateral strike-slip Haiyuan fault system is a major boundary fault zone in the northeastern Tibetan Plateau, which is made by several segments including the Tuolai Shan fault (TLS F.), the Leng Long Ling fault (LLL F.), the Jin Qiang He fault (JQH F.), the Lao Hu Shan fault (LHS F.), the Mao Mao Shan fault (MMS F.), and the Haiyuan fault (HY F.) (Liu et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Xiong et al., 2018; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Earthquakes occur frequently in the Haiyuan fault system and surrounding area, including two M\u003csub\u003ew\u003c/sub\u003e\u0026gt;7.5 events: the 1920 M\u003csub\u003ew\u003c/sub\u003e 7.8 Haiyuan earthquake and the 1927 M 7.9 Gulang earthquake, which produced 240 km and 140 km long surface rupture, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). To the west of the 1920 Haiyuan earthquake lies the Tianzhu seismic gap, a 260-km-long fault zone, which has not experienced M\u003csub\u003ew\u003c/sub\u003e\u0026gt;7.0 earthquake in more than 800 years (Gaudemer et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Jolivet et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eOn January 8th, 2022, an M\u003csub\u003ew\u003c/sub\u003e 6.7 earthquake stuck the west segment of Tianzhu seismic gap, causing\u0026thinsp;~\u0026thinsp;20-km-long surface rupture and significant ground deformation. The Lanzhou-Xinjiang high-speed railway, which passed through the causative fault, is forced to shutdown temporarily. The epicentre of the earthquake is located \u0026sim;50 km northwest of the city of Menyuan (USGS, 2022). Source mechanism solutions from teleseismic data (USGS, 2022; GCMT, 2022; Table\u0026nbsp;1) indicate that the 2022 Menyuan earthquake ruptured a steeply dipping strike-slip fault, which is consistent with the slip behaviour of the Haiyuan fault system. The distribution of the relocated aftershocks (Fan et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) confirms that the mainshock ruptured a bending section of the LLL fault, named Liuhuanggou segment, where the LLL fault intersects with the TLS fault.\u003c/p\u003e \u003cp\u003eAs the most lately strong event on the Tianzhu seismic gap, the 2022 Menyuan earthquake attracted a lot of attentions. Although the seismogenic fault locates in high altitude area with sparse GPS observations, the coseismic deformations associated with the 2022 Menyuan earthquake are recorded by spaceborne Interferometric Synthetic Aperture Radar (InSAR) and optical images. Consequently, the InSAR-derived coseismic deformation and the coseismic slip model (e.g., Li et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Liu et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Yang et al., 2022) are quickly presented. However, the coseismic deformation derived from offset tracking method has not been reported yet. Besides, the seismogenic environment of the earthquake and the potential seismic hazard on Tianzhu seismic gap after the earthquake need further investigation.\u003c/p\u003e \u003cp\u003eIn this study, we map the coseismic deformation fields of the Menyuan earthquake by the Sentinel-1 SAR interferograms.. Then, we perform simultaneous inversions for coseismic slip model using the InSAR and near-field pixel-offset data. Besides, we discuss about the interactions the 2022 earthquake and historical events, as well as the potential seismic hazard on western Tianzhu gap.\u003c/p\u003e"},{"header":"2. Data and Method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Geodetic observations\u003c/h2\u003e \u003cp\u003eIn this study, we collected Synthetic Aperture Radar (SAR) data from the European Space Agency (ESA) Copernicus Sentinel-1A with Terrain Observation with Progressive Scan (TOPS) mode to measure the displacements caused by the 2022 Menyuan event. Fortunately, there are two ascending (T026A, T128A) and one Descending track (T033D) captured the deformation field caused by this event(Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). All SAR data were processed by GAMMA software (Werner and Wegm\u0026uuml;ller 2000) flowing the general DInSAR workflow. A 90 m Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) (Farr et al. 2000) was used to remove the effects of topography. To improve the signal-to-noise ratio of the interferogram, the interferogram in both the ascending and descending were then filtered with an adaptive power spectral filter (Goldstein and Werner \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1998\u003c/span\u003e) to suppress phase noise. Because the deformation gradient is too high in near faults will cause the problem in phase unwrapping, we Masked low coherence areas in the interferogram with the coherence threshold is 0.3 before unwrapping.the differential phase is unwrapped using the minimum cost flow algorithm (MCF), and geocoding is performed to obtain the deformation in geographic coordinates. Due to the dry environmental condition in the study area, the interferometric phase in both the descending and ascending track look very clear and undisturbed. Fianlly we modeled residual orbital errors by applied a polynomial function and removed from the interferograms.\u003c/p\u003e \u003cp\u003eAs the the unwrapped phases were missing near the faults ,we use the pixel offset tracking(POT) method to detect the robust large deformation signals (Tobita et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Kobayashi et al. 2009; Takada et al. 2009).The processing strategy refer to previous studies, we use the GAMMA software to do fine coregistration of SAR images before the POT analysis and then used autonomous repeat image feature tracking (autoRIFT) algorithm to calculate the POT deformation. we set the matching window size to 256x128 pixels for range and azimuth in order to improve POT accuracy.. There is a 3 m threshold was Selected to remove the Singularities with magnitude above the threshold (Yang et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Finally the resultant offset maps was filtered by a Gaussian smoothing filter and geocoded in WGS84 coordinates.\u003c/p\u003e \u003cp\u003eAll three interferograms with high spatial resolution and good covrage in the study area result in millions of measure points ,leading to huge computation burdens.we used a A efficient and reliable quadtree down-sampling method to downsample the InSAR deformation field.We set the search mim windows size, max windows size and Segmentation threshold is 8, 256 and 0.1 respectively. Finally, For the cosesimic deformation, 778, 1030, 812, and 661 data points were retrieved from the T026A, T128A, T033D and T033D range offsettracking, respectively. For the post-seismic deformation, we get 1107 and 1076 data point for the T128A, T033D track, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Model configuration\u003c/h2\u003e \u003cp\u003eWe inverted the co-seismic slip distribution of the 2022 menyuan mainshocks(Mw6.7) based on the descending and ascending observation data of Sentinel-1A. We adopted the steepest descend approach (SDM) algorithm based on the multi layered earth model ,which establishes a linear relationship between coseismic surface displacement and fault dislocation distribution after the fault geometry is determined(Wang et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). In order to get a smoothing slip model, it introduced a physical constraint to ensure the stability of the inversion that can be solved by a roughness term that is minimized in terms of data misft. a smooth stress drop is applied on the entire fault in our study.\u003c/p\u003e \u003cp\u003eThe aftershock refined sequences distribution is 23 Km in the NWW direction, which is generally consistent with the fault trace captured by the range offset-tracking result.The aftershocks were concentrated at depths of 4 to 12 km (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.cea-igp.ac.cn/kydt/278812.html\u003c/span\u003e\u003cspan address=\"https://www.cea-igp.ac.cn/kydt/278812.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). we constructed a rectangular fault plane with length and width were extended to 40 km along fault tract and 30 km following the down dip, respectively and the plane was divided into subpatches with sizes of 1km x 1km. According to the to the seismic geological data and the focal mechanism solution given by many institutions, the dip angle of the plane set a range from 60\u003csup\u003eo\u003c/sup\u003e to 90\u003csup\u003eo\u003c/sup\u003e. a grid search was applied to search for the optimal dip angle is 85\u003csup\u003eo\u003c/sup\u003e, which realized through minimizing data misfit. As mentioned above, the smoothing factor is usually estimated by the trade-off curve between the stress roughness of the model and the ftting residuals.We chose the inflection point in the curve line as our appropriate smoothening factor is 0.06. All Green\u0026rsquo;s functions were calculated with the Crust 2.0 crustal model (Bassin et al.,2000).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Co-seismic displacements\u003c/h2\u003e \u003cp\u003eThe fringe patterns are Continuous and clear except for the decoherence area near the fault caused by high deformation gradient in both ascending and descending track. The fringe patterns in descending interferogram is almost completely symmetrical, covers a butterfly-shape while the number of fringes on both sides of the fault is similar in the ascending and descending orbit indicates that the seismogenic fault is strike-slipping fault with high dip angle. The LOS deformation were \u0026minus;\u0026thinsp;0.56\u0026thinsp;~\u0026thinsp;0.51m, -0.36\u0026thinsp;~\u0026thinsp;0.65m and \u0026minus;\u0026thinsp;0.30\u0026thinsp;~\u0026thinsp;0.68m for T033D,T128A and T026A track respectively(Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn contrast to the LOS deformation accuracy, the offset maps accuracy is very limited and can only reach the decimeter level (Li et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). unfortunately, only the descending T033D Track in range offset map could capture the significant pixel-offset by as much as ~\u0026thinsp;1m. It is important that the fault trace can be clearly observed from range offset maps, but is decorrelation caused by the surface ruptures in the LOS deformation map. In this study, the fault trace is used to constrain the fault model orientation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Co-seismic slip\u003c/h2\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d), The menyuan earthquake caused a surface rupture. The .The slip distribution is characterized by nearly purely left-lateral strike-slip with an average rake of 4.00◦ and an average slip of 0.13 m.The maximum slip is 3.5m at the depth of 4-5km and the seismic moment is about 1.8\u0026times;10\u003csup\u003e19\u003c/sup\u003e N m (assuming a rigidity of 3.2\u0026times;10\u003csup\u003e10\u003c/sup\u003e Pa),which is is equivalent to moment magnitude M\u003csub\u003eW\u003c/sub\u003e 6.7. As the observation and prediction correlation was 0.968, our model can sufficiently explain InSAR observations with RMS are 0.02m 0.02 and 0.01m for tracks T026A, T128A and T033D. The larger residuals with amplitude up to 4\u0026thinsp;~\u0026thinsp;5cm was mainly distributed nearby the fault trace in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c). This RMS may primarily due to the simplified fault plane could not reproduce the high deformation gradients caused by the stepping geometry of real fault.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e4.1. A cascade rupture associated with the 2022 Menyuan earthquake\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eThe bulk of the coseismic slip associated with the 2022 Menyuan earthquake is located on LLL fault. The back-projected results suggest a relatively low rupture velocity (1.0-1.2 km/s) (Yang et al., 2022), which is consistent with the bending fault trace (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), for the curved fault geometry is not conducive to the acceleration of fracture. The rupture involved not only the mapped fault trace, but also an unmapped\u0026thinsp;~\u0026thinsp;6-km-long section which appears as a western extension of the Liuhuanggou segment (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The LLL fault, together with the TLS fault and Sunan-Qilian fault, form a brush structure, which convergent SE-wards and divergent NW-wards (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The brush structures are widely developed at the end of strike-slip faults, e.g. the Altyn Tagh fault (Li et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), and always present tensional property. The latter could explain the tensional cracks reported by field investigation (Han et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) and the normal-slip component in our coseismic slip model (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAlthough the slip on TLS fault is not as significant as that on LLL fault (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), the surface rupture (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) reveals that the eastern section of TLS fault is involved in the coseismic period, resulting a joint rupture associated with the 2022 Menyuan earthquake. Several large earthquakes with cascade rupture are reported near Haiyuan fault zone (e.g. the 1920 M\u003csub\u003ew\u003c/sub\u003e 7.9 Haiyuan earthquake, Ou et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; the 1927 M7.9 Gulang earthquake, Guo et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). However, the 2022 Menyuan earthquake provided a rare instance, in which an M\u003csub\u003ew\u003c/sub\u003e 6.7 earthquake induced a complex cascade rupture. It appears that the coseismic rupture did not propagate directly from the LLL fault to the TLS fault, for the ~\u0026thinsp;3-km-long surface rupture gap on the TLS fault (Han et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The surface rupture gap indicates a probably step-over locates between the LLL fault and TLS fault, which always acts as a barrier in the process of rupture propagation. The rupture on the TLS fault could be partly due to the stress transfer process (Stein, 1997), for the coseismic Coulomb stress change (dCFS) caused by the slip on LLL fault significantly raised the stress level on the region with surface rupture on the eastern TLS fault (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). In addition, the surface rupture gap is covered by the stress shadow, in which the fault could be temporarily silenced by the stress release (Harris \u0026amp; Simpson, 1998).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e4.2. Limited coseismic slip and high stress drop of the mainshock\u003c/h2\u003e \u003cp\u003eThe 2022 M\u003csub\u003ew\u003c/sub\u003e 6.7 Menyuan earthquake produced a shallow coseismic rupture with peak slip of 3.15 m. Although it is infrequent for an M\u003csub\u003ew\u003c/sub\u003e 6.7 earthquake to produce\u0026thinsp;~\u0026thinsp;20-km-long surface rupture, shallow ruptures are not uncommon on strike slip faults in the eastern margin of the Qinghai-Tibet Plateau. For instance, the rupture of the 2010 M\u003csub\u003ew\u003c/sub\u003e 6.8 Yushu earthquake concentrates in a depth range of 0\u0026ndash;10 km (Wen et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Similar shallow rupture is also found in the 2021 M\u003csub\u003ew\u003c/sub\u003e7.4 Maduo earthquake (e.g. Zhao et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The phenomenon is probably attributed to the thin sedimentary cover, whose thickness is 0\u0026thinsp;~\u0026thinsp;0.5 km in the eastern margin of the Qinghai-Tibet Plateau (Laske et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), for the sediments commonly present \u0026ldquo;weak\u0026rdquo; frictional property and behave as barriers for dynamic ruptures (Gabriel et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Yue et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eHowever, the rupture dimensions and the magnitude of the coseismic slip associated with the 2022 event are worth mentioning. The bulk of the rupture (with slip larger than 0.5 m) concentrates in a 23 km \u0026times; 10 km area, which is much smaller than the rupture area predicted by the empirical relationship from Wells \u0026amp; Coppersmith (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). The latter suggests a rupture size of 38.4 km \u0026times; 12 km. Moreover, the value of the peak slip (3.15 m), which is much larger than the predicted value of \u0026sim;0.7 m (Wells \u0026amp; Coppersmith, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1994\u003c/span\u003e), is probably the largest documented coseismic slip induced by M\u003csub\u003ew\u003c/sub\u003e \u0026lt; 7 events in Chinese mainland. The characteristics of the coseismic slip are comparable with that in the 2016 M\u003csub\u003ew\u003c/sub\u003e 6.2 Tottori, Japan earthquake (Ross et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and the 2020 M\u003csub\u003ew\u003c/sub\u003e 6.4 Petrinja, Croatia earthquake (Xiong et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The latter ruptured a\u0026thinsp;~\u0026thinsp;45 km\u003csup\u003e2\u003c/sup\u003e patch with a peak slip of 3.5 m. The 2022 Menyuan earthquake occurred on the west end of the bending LLL fault. The causative fault intersects with the Lenglongling North fault on ~\u0026thinsp;101.35\u0026deg;E, which is near the eastern end of the surface rupture (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The limited length and complex geometry of the causative fault is ideal to confine the rupture propagation, and thus yielding high coseismic slip on a small fault plane (Wang et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eLarge coseismic slip limited within a small area always leads to large stress drop on the fault plane (Ross et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Zielke et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Xiong et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The stress drop of the 2022 Menyuan earthquake is estimated using the method of Stein \u0026amp; Wysession (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). The maximum stress drop is approximately 14 MPa, which is much larger than the empirical values of \u0026sim;5 MPa for large earthquakes or 1\u0026ndash;2 MPa for moderate earthquakes (Zielke \u0026amp; Arrowsmith \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). The estimated stress accumulation rate on LLL fault is ~\u0026thinsp;1.2 MPa/100\u0026nbsp;year (Li et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The stress drop of the 2022 earthquake is equivalent to ~\u0026thinsp;1100 years of tectonic loading. The large stress drop highlights the high stress accumulation on the west section of the Tianzhu seismic gap, which has not experienced strong earthquakes for centuries.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e4.3. Stress transfer and potential seismic hazard on western Tianzhu seismic gap\u003c/h2\u003e \u003cp\u003eThe seismic hazard on Tianzhu seismic gap is widely concerned, although part of the fault (e.g. the eastern segment of the LLL fault) is probably ruptured during the 1927 M7.9 Gulang earthquake (Guo et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Previous studies suggested that the seismic risk on western Tianzhu seismic gap is higher than the eastern part, for the stress shadow on the latter caused by historical earthquakes (e.g. Xiong et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) and shallow aseismic creep on the LHS fault (e.g. Jolivet et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Huang et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). This conclusion is partly proved by the occurrence of the 2022 Menyuan earthquake, which caused a joint rupture on western LLL fault and the TLS fault. Here, we present a further discussion about the potential seismic hazard on western Tianzhu seismic gap with stress transfer theory (Stein, 1997) and GPS-derived velocity field (Wang \u0026amp; Shen, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eStress transfer theory has been widely used to assess the seismic risk on active faults (e.g. Freed, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Stein, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). Subsequent earthquakes always occur in the stress loading area caused by historical earthquakes, and the faults located in stress shadow would be silenced by the stress release (e.g. Stein et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; McCloskey et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Before the occurrence of the 2022 Menyuan earthquake, the dCFS caused by historical earthquakes produced a\u0026thinsp;~\u0026thinsp;80-km-long stress loading area on the western Tianzhu gap, in which the dCFS is larger than 0.1 MPa (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). Unsurprisingly, the 2022 Menyuan earthquake is occurred in the stress loading area, with a dCFS value of ~\u0026thinsp;0.17 MPa on the epicentre (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec), corresponding to ~\u0026thinsp;14 years of tectonic loading. The results are stable in different simulations with variable parameters (e.g. effective friction coefficient, viscosity coefficient), indicating that the occurrence of the 2022 event is probably promoted by the historical earthquakes. More importantly, the rupture of the 2022 event did not fill the stress loading area on the western Tianzhu gap, and the coseismic dCFS caused by the 2022 event has further enhanced the stress level on the eastern TLS fault, resulting a\u0026thinsp;~\u0026thinsp;40-km-long segment with stress loading larger than 0.1 MPa (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb; Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe potential seismic hazard on western Tianzhu gap is not only evidenced by dCFS results, but also by geodetic-derived slip rate and interseismic coupling on the fault plane. Based on the newly GPS-derived velocity field (Wang \u0026amp; Shen, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), we present a simple 2D model (Savage \u0026amp; Burford, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1973\u003c/span\u003e) to obtain the sinistral slip rate and interseismic coupling on the eastern TLS fault (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec). The statistical distribution of the slip rate and locking depth inferred from 500 Monte Carlo simulations (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed). The dislocation model suggests that the slip rate on the fault is 6.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46 mm/a, but with a locking depth of 72.2\u0026thinsp;\u0026plusmn;\u0026thinsp;12.3 km, which is much deeper than the seismogenic thickness in this region (~\u0026thinsp;20 km; Laske et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The result indicates that the fault plane may be fully locked to the base of the seismogenic zone. In the context, we fixed the locking depth at 20 km, and the constrained model suggests a slip rate of 5.37\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14 mm/a (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed), which is comparable with the results of Li et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) and Huang et al. (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The fully locked fault plane is one of the key characteristics in the late period of earthquake cycle, and thus highlights the potential seismic risk on the western Tianzhu gap.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eIn this study we described the co-seismic deformation caused by the 2022 Menyuan earthquake using Sentinel-1A observations. We used offset-pixel tracking deformation to obtain the fault trace and use Interferograms to constrain the deformation pattern. On the basis of InSAR observations, a finite dislocation model was implemented to invert the geometrical parameters of the causative fault and the slip distribution of the fault plane. Our inversion results show that the seismogenic fault rupture was dominated by strike-slip and was primarily on the LLL fault with one main asperity was concentrated at depths of 0\u0026ndash;10 km covered 23 X 10 km2 as well as the TLS fault with a small size of 5\u0026times;5 km2 at depths of 0\u0026ndash;8 km. Although the 2022 menyuan earthquake cause the large stress drop on the west section of the Tianzhu seismic gap where is the high stress accumulation, we still highlight the potential seismic risk on western Tianzhu gap is high according to the dCFS results caused by historical earthquakes in TLS fault and geodetic-derived slip rate and interseismic coupling on the fault plane.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eChen. Wei and Xiong. Wei wrote the main manuscript text , Wen Yangmao calculated the SAR data, Zhao Bin established the coseismic model and Qiao Xuejun prepared figures in this manuscript. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe Sentinel-1 IW data were downloaded from Alaska Satellite Facility (ASF) Vertex at https://search.asf.alaska.edu/#/. Figures are prepared by using Generic Mapping Tools (Wessel et al., 2013). We are grateful for this support and help.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBassin, C., Laske, G., and Masters T.G. (2000). The current limits of resolution for surface wave tomography in North America. \u003cem\u003eEOS Trans. AGU\u003c/em\u003e, 81, F897.\u003c/li\u003e\n\u003cli\u003eFan, L. P., Li, B. R., Liao, S. R., et al. (2022). High-precision relocation of the aftershock sequence of the January 8, 2022, MS6.9 Menyuan earthquake. \u003cem\u003eEarthq Sci\u003c/em\u003e 35(2): 138\u0026ndash;145,. doi: 10.1016/j.eqs.2022.01.021\u003c/li\u003e\n\u003cli\u003eFarr, T. G., Kobrick, M. (2000). 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Depth variation of coseismic stress drop explains bimodal earthquake magnitude‐frequency distribution.\u003cem\u003e Geophysical Research Letters\u003c/em\u003e, 35(24).\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":"pure-and-applied-geophysics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"paag","sideBox":"Learn more about [Pure and Applied Geophysics](https://www.springer.com/journal/24)","snPcode":"24","submissionUrl":"https://submission.nature.com/new-submission/24/3","title":"Pure and Applied Geophysics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Menyuan earthquake, Tianzhu seismic gap, InSAR, stress accumulation","lastPublishedDoi":"10.21203/rs.3.rs-4212637/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4212637/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe January 8th 2022 menyuan earthquake(Mw6.7) occurred along major boundary fault zone in the northeastern Tibetan Plateau.In this study, we derived the co-seismic deformation from pixel offset tracking (POT) and interferometric synthetic aperture radar (InSAR) by using Sentinel-1 data. The inteferograms pattern shows that coseismic deformation is dominated by horizontal movements with the maximum displacement are over 0.5m in both tracks and POT results. Then we inverted the geometry parameters of the causactive fault and the slip distribution of the fault plane based on the finite dislocation model. The result shows the seismogenic fault has an average strike of 108.0\u003csup\u003e◦\u003c/sup\u003e and a northeast dip angle of 83\u003csup\u003e◦\u003c/sup\u003e. moreover, the coseismic slip is primarily concentrated on the lenglongling fault with on main asperity of 10 X 23 km and the maximum slip of 3.5m at depth of 4km as well as rupture the eastern of the tuolaishan fault with a small area of 5\u0026times;5 km at depths of 0\u0026ndash;8 km. On the basis of the dCFS results caused by historical earthquakes in tuolaishan fault and geodetic-derived slip rate of the tuolaishan fault, we emphasize the potential seismic risk on western Tianzhu gap is high.\u003c/p\u003e","manuscriptTitle":"The 2022 M w 6.7 Menyuan earthquake: a cascade rupture reveals the high stress accumulation on the west section of Tianzhu seismic gap","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-10 03:48:37","doi":"10.21203/rs.3.rs-4212637/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-05-27T15:02:57+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-05-24T06:47:06+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-05-14T01:08:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"91419768379524276887634631735456966790","date":"2024-05-06T21:16:46+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"e131a703-9bd5-4d03-940b-f7d863b4f3da","date":"2024-04-23T03:15:12+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-04-08T11:04:41+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-05T14:57:59+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-04-05T14:57:41+00:00","index":"","fulltext":""},{"type":"submitted","content":"Pure and Applied Geophysics","date":"2024-04-03T12:13:01+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"pure-and-applied-geophysics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"paag","sideBox":"Learn more about [Pure and Applied Geophysics](https://www.springer.com/journal/24)","snPcode":"24","submissionUrl":"https://submission.nature.com/new-submission/24/3","title":"Pure and Applied Geophysics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"02022e74-6efc-4df8-9cb1-425b69ac83a9","owner":[],"postedDate":"April 10th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-08-05T16:11:12+00:00","versionOfRecord":{"articleIdentity":"rs-4212637","link":"https://doi.org/10.1007/s00024-024-03544-7","journal":{"identity":"pure-and-applied-geophysics","isVorOnly":false,"title":"Pure and Applied Geophysics"},"publishedOn":"2024-08-01 15:58:21","publishedOnDateReadable":"August 1st, 2024"},"versionCreatedAt":"2024-04-10 03:48:37","video":"","vorDoi":"10.1007/s00024-024-03544-7","vorDoiUrl":"https://doi.org/10.1007/s00024-024-03544-7","workflowStages":[]},"version":"v1","identity":"rs-4212637","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4212637","identity":"rs-4212637","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}