Subsurface structures of the Tuaheni Landslide Complex at the upper slope of the northern Hikurangi margin, New Zealand, revealed by seismic attribute analysis

Subsurface structures of the Tuaheni Landslide Complex at the upper slope of the northern Hikurangi margin, New Zealand, revealed by seismic attribute analysis | 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 Article Subsurface structures of the Tuaheni Landslide Complex at the upper slope of the northern Hikurangi margin, New Zealand, revealed by seismic attribute analysis Uma Shankar, Maheswar Ojha, Ranjana Ghosh This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2045866/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Tuaheni Landslide Complex, located on the upper slope of the northern Hikurangi margin in New Zealand, is a unique location to study slow slip creep-like deformation and seafloor failure, as well as their possible relationship to the presence of gas hydrate, cold seeps, and fluid migration. Based on the visual interpretation of seismic data, sometimes it is very difficult to identify various subsurface structures and tectonic features. We study certain seismic attributes namely reflection-strength, instantaneous frequency, instantaneous phase, and Hilbert Transform in the Tuaheni Landslide Complex and observe that these attributes play a very important role to identify and interpret various subsurface geological features, which are not visible in the seismic sections. These seismic attributes nicely illustrate the fluid migration pathways, the decollement of the sediment slide, the base of the debris flow, the base of the deformed sediment and gas migration, etc. along two perpendicular seismic profiles crossing the well Site U1517 of IODP Expedition 372. The possible role of tectonic activity and seafloor slope failure due to gas hydrate dissociation and vice versa are clearly visible through fluid-filled weak zones in the seismic attribute volumes. Seismic attributes gas hydrate reflection strength instantaneous frequency Hikurangi margin New Zealand. IODP Expedition 372 Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction One of the seismically active areas on the Earth is the northern Hikurangi margin, where the presence of gas hydrates, fluid migration, cold seeps, and creep-like deformation is thought to be responsible for frequent earthquakes, slow slip events, submarine landslides causing Tsunami, and high tides1,2,3,4,5,6 . The presence of gas hydrate in the Tuaheni Landslide Complex (TLC) on the upper slope of the northern Hikurangi margin (Fig. 1) has been inferred by identifying discontinuous bottom simulating reflectors (BSR) on the multi-channel seismic volume7,8,9,4,5,6,1,2,3. However, the BSR is not completely following the topography of the seafloor and is rapidly wrapping upward (Fig. 2), which may be caused by regional thermal anomalies, cold seeps, and fluid migration2,3,6. Various seismic attributes like reflection strength, instantaneous frequency, instantaneous phase and Hilbert transform are very useful to interpret various subsurface features, which are not always possible to see directly from the seismic section. The presence of gas-hydrates and free-gas changes the sediment properties in various ways, which have been characterized by various seismic attributes like reflection strength and instantaneous frequency in various world margins such as Blake Ridge, Vring Plateau off Norway, Indian offshore, Shenhu area of South China sea, Makran Accretionary Prism, Ulleung Basin offshore South Korea etc10,11,12,13,14,15,16,17,18,19,20,21,22. Gas hydrates in sediment pore spaces reduce the sediment porosity and thus seismic impedance contrasts between units within gas hydrate-bearing sediments, resulting in lower seismic reflection amplitudes and making the seismic section transparent23. Sediment velocity is increased by the presence of gas hydrates, while free gas in the pore spaces beneath the BSR greatly reduces seismic velocity, changing the impedance contrasts across the BSR15. On the other hand, gas-charged sediments absorb lots of seismic energy and show low-frequency dominance in the instantaneous frequency section24. During the recent drilling at Site U1517 under the International Ocean Drilling Program (IODP) Expedition 372 in 2018, gas hydrate-bearing reservoirs were documented up to 160m below the seafloor and at water depths between 600 and 1000 m4. In this study, we interpret reflection strength, instantaneous frequency, instantaneous phase and Hilbert transform of an in-line and a cross-line multi-channel seismic section crossing the well location in the northern Hikurangi margin to identify and analyse various subsurface structures/features associated with the presence of gas hydrate, free gas, fluid migration pathways, sediments slides, tectonic activity etc. Study Area And Data The Hikurangi margin is located off the East Coast of the North Island of New Zealand. It is characterized by the subduction of the Pacific Plate beneath the Australian Plate (Fig. 1 ). The plate convergence occurs obliquely towards the SW 25 . The oblique convergence separates subduction thrust, and margin normal and parallel components. The Hikurangi margin is further influenced by mass transport deposits and the subduction of various seamounts on the oceanic plate 26 , 27 . The northern Hikurangi margin includes numerous seamounts on the subducting Pacific plate and is categorized by a combination of tectonic erosion in the north and limited accretion developed further south 28 , 29 . At the northern Hikurangi margin, the Pacific plate subducts beneath the Australian plate (eastern North Island, New Zealand) at a rate of 4.5–5.5 cm/year 4 as shown in Fig. 1 . The oceanic subducting plate comprises the Hikurangi Plateau, a rough-crust, seamount-studded large igneous province of Cretaceous age (120–90 Ma), which is part of ~ 600 km long off eastern North Island 1 . Hikurangi Margin marks the boundary between the obliquely convergent Pacific plate and Australian plate and the portion where the oceanic crust of the Pacific Plate subducts beneath the continental crust of the Australian Plate and New Zealand North Island 2 . Geophysical data modeling of the Hikurangi plateau shows the oceanic plate is subducted beneath the northern Island 30 . The stratigraphy and structure of the Hikurangi margin contain pre-subduction and Neogene subduction systems 2 . The geology comprises an imbricated accretionary wedge. The wedge consists of three major stratigraphic groups: an inner foundation of pre-subduction rocks consisting of late Cretaceous and Paleogene rocks, an outer wedge of Pliocene to Pleistocene accreted trench-filled turbidites, and a deforming cover sequence of Miocene to the recent shelf and slope basin sediments 2 , 31 . Barnes et al. 2 observed numerous deformed rocks on seismic images, which could be associated with active thrust faulting and folding in Miocene. The IODP 372 expedition discovered five major litho-units at Site U1517: i) the top four meters below the seafloor with silty-clay and clayey-silt layer, ii) 4–40 meters below seafloor (mbsf) with alternate sand and mud layers, iii) 40–67 mbsf with alternate silt and clay layers, iv) 67–103 mbsf with silty-clay and clayey-silt, and v) 103–187 mbsf as a mixture of above four units 20 . Later, seven litho-units were observed along seismic profiles based on the acoustic impedance and porosity inversion 8 . In this study, seismic data from a 3D seismic volume were extracted for scientific investigation purposes in the northern Hikurangi margin of New Zealand 4 . Seismic data has a high-frequency content of about 220 Hz, with a dominant frequency of about 90 Hz. The seismic data sets were used for site selection and drilling targets for the IODP 372 Expedition before gas hydrate exploration. Figure 2 depicts an in-line seismic section oriented along NW-SE and a cross-line seismic section oriented along SW-NE crossing Site U1517 drilled at 720 m water depth 20 . The drilling site is located within the 3D seismic survey area in the Tuaheni landslide complex, where logging while drilling (LWD) and wire-line loggings (WL) were performed. Mainly, resistivity and velocity logs were used to identify and estimation of gas hydrate in the study area. The seismic sections (Figs. 2 a and 2 b) reveal distinct BSRs in the steep slope region, followed by a high reflectivity zone at and below the base of the gas hydrate stability zone (BGHSZ) with the decollement of landslide and the base of debris flow 20 . Seismic Attributes Seismic attributes are some information extracted from the seismic data to enhance the subsurface geological features. Instantaneous amplitude and instantaneous phase are the two fundamental seismic attributes used in complex seismic trace analysis. Many attributes are derived from these two main attributes - amplitude and phase, through differentiation, averaging, combination, or transformation. Instantaneous attributes are defined at every point on the seismic trace. Since the seismic trace is insufficient to separate instantaneous amplitude and phase, the quadrature trace is first calculated from the seismic trace using the Hilbert transform. The colour displays of seismic attributes are used for the interpretation of geologic structures, stratigraphy, and rock/pore fluid properties. The instantaneous amplitude or trace envelope is a measure of brightness or reflection strength and it is independent of phase and polarity. It is sensitive to changes in acoustic impedance, thus to lithology, porosity, hydrocarbons and thin-bed tuning 22 , 32 . The presence of gas hydrate increases the acoustic impedance, whereas, the presence of even a small amount of free gas decreases the acoustic impedance. The instantaneous phase is used to track reflector continuity to detect unconformities, faults and lateral changes in stratigraphy when the phase angle cannot be followed from trace to trace 22 , 33 . Instantaneous frequency can be used to identify abnormal attenuation 22 and thin bed tuning 33 . Since many reflector events are a composite of individual reflections from closely spaced reflectors or tuning of multiple impedance contrasts, a characteristic reflection frequency pattern is produced. This character of a composite reflection changes gradually as the sequence changes laterally in thickness or lithology. Another useful application of instantaneous frequency is to identify sediments that give seismic attenuation, such as gas sands because they highly attenuate seismic P waves by absorbing high-frequency content and therefore low-frequency shadows are observed. Gas hydrates also appear to attenuate energy as discussed above, but not as much as gas-bearing sediments 24 . Most attributes have a noisy character since they are derived through differentiation, which introduces less coherent high frequencies and suppresses more coherent low frequencies. Also, because the instantaneous amplitude and phase have inflection points and discontinuities, their differentiation results in spurious spikes. The instantaneous attributes are also spiky and noisy because of the noise in the data. The most anomalous values of instantaneous frequency are most often associated with small amplitudes and are the least reliable, whereas the ones associated with larger amplitudes are more stable 34 . To remove the high-frequency noise and spikes to ease interpretation by emphasizing the frequency of stronger reflectors, the instantaneous attributes are filtered. The most common filters are the median filtering, which is the selection of instantaneous attributes at envelope peaks and weighted averaging by the instantaneous power or envelope squared 35 . The conventional seismic trace \(x\left(t\right)\) can be represented as the real component of a complex seismic trace \(z\left(t\right)\) . The imaginary component \(y\left(t\right)\) is called the quadrature trace as given below, $$z\left(t\right)=x\left(t\right)+i.y\left(t\right)$$ 1 . The quadrature trace is determined from \(x\left(t\right)\) by convolution in the time domain using the Hilbert transform quadrature filter \(h\left(t\right)\) , such that, $$y\left(t\right)=h\left(t\right)*x\left(t\right)$$ 2 , where, $$h\left(t\right)=1/\left(\pi t\right)$$ 3 The Fourier transform of \(h\left(t\right)\) is defined as, $$H\left(f\right)=\left\{\begin{array}{c}-i, f>0\\ +i, f< 0\\ 0, f= 0\end{array}\right.$$ 4 , where, \(f\) is frequency. A phase rotator \(p(t,\varphi )\) that subtracts an angle \(\varphi\) is given by, $$p\left(t,\varphi \right)=\delta \left(t\right)cos\varphi +h\left(t\right)sin\varphi ,$$ 5 where, \(\delta\) is the delta function. When applying the phase rotator to a seismic trace \(x\left(t\right)\) and using Eq. 2 , the trace is rotated as, $$x\overline{\left(t\right)}=p(t,\varphi )*x\left(t\right)=x\left(t\right)cos\varphi +y\left(t\right)sin\varphi$$ 6 . The rotated trace under a phase rotation of 90 o is the Hilbert transform ( \(x\overline{\left(t\right))}=y\left(t\right),\) resulting in a quadrature trace 22 . The quadrature trace does not have any physical meaning. Peaks and troughs on the quadrature trace correspond to zero crossing on the seismic trace 36 . The trace envelope \(a\left(t\right)\) is defined as the maximum value that a seismic trace can have under a constant phase rotation, which makes it independent of phase. The trace envelope can be described as a function that connects the waveform peaks, as well as troughs since it is independent of polarity. If \(\varphi \left(t\right)\) represents the angle that maximizes the value of the rotated trace, Eq. 6 can be written as, $$a\left(t\right)=x\left(t\right)cos\varphi \left(t\right)+y\left(t\right)sin\varphi \left(t\right)$$ 7 . Equation 7 is equivalent to $$\frac{\delta a\left(t\right)}{\delta \varphi \left(t\right)}=0=-x\left(t\right)sin\varphi \left(t\right)+y\left(t\right)cos\varphi \left(t\right)$$ 8 . Because when the trace envelope equals the rotated seismic trace (at maximum), its change with respect to the rotation angle is zero. The trace envelope derives from equations 7 and 8 as, $$a\left(t\right)={{(x}^{2}\left(t\right)+{y}^{2}\left(t\right))}^{0.5}$$ 9 . The angle ( \(\varphi\) ) that rotates the trace to a maximum, or instantaneous phase is derived from Eq. 8 as, $$\varphi =arctan\frac{y\left(t\right)}{x\left(t\right)}$$ 10 . The instantaneous phase has a saw tooth appearance and its values range from (-π, π). They refer to the apparent position along the seismic trace, such that peaks have 0 o phase, trough has 180 o phase, and downward zero crossing has − 90 o phase. If the seismic trace is represented by a cosine wave with amplitude \(a\left(t\right)\) , the quadrature trace is a sine wave with the same amplitude. A complex-valued signal from Eq. 7 can be written as, $$z\left(t\right)=a\left(t\right)\text{e}\text{x}\text{p}\left(i\varphi \left(t\right)\right)$$ 11 . The instantaneous frequency represents the rate of change with the time of the instantaneous phase divided by 2π 22 , $$f\left(t\right)=\frac{1}{2{\pi }}\frac{d\varphi }{dt}$$ 12 , \(f\left(t\right)\) has units of Hz, but it is not a frequency in the physical sense, as it has negative values at inflection points of the trace and can also exceed the maximum frequency in the signal when the trace is close to zero and crosses it for one or two samples. Results And Discussion Four seismic attributes namely reflection strength, instantaneous frequency, instantaneous phase and Hilbert transform calculated along the in-line and cross-line profiles. These attributes are clearly illustrating various subsurface features like slipped sediment, decollement, the base of debris flow and deformed sediments, pinch outs, BSR, gas-charged sediments, gas migration etc. in the Tuaheni Landslide Complex on the upper slope of the northern Hikurangi margin, New Zealand. All interpretations are dawn based on four seismic attributes, where some features are visible on some attributes and others are on other attributes. Reflection strength plots along two seismic lines (Fig. 3 ) show various features demarcated by the contrast between low and high reflection strength. BSR is clearly illustrated by the very high reflection strength of underlying gas-charged sediments. The base of the slipped sediment, debris and deformed sediments and decollement, which are in generally water-filled zones are demarcated by low reflection strength lineaments. Slipped sediment is not there on the cross line. Scattered high reflection strengths are observed in the debris flow and deformed sediments within the hydrate stability zone, which is possibly because of the dissociation of gas hydrate due to the tectonic activity. The instantaneous frequency plot generally depicts the presence of gas as low-frequency shadow as shown in Fig. 4 . Presence of free gas within the sediments, below the BSR, upward movement of free gas, and velocity pulled down because of lowering velocity due to gas are clearly observed in Fig. 4 . This interpretation is consistent with observations from the Blake Ridge 24 , the Vring Plateau off Norway 19 , the Makran accretionary prism 15 , the Ulleung basin 10 , 14 , and the South China Sea 13 . The instantaneous phase attribute is independent of the amplitude used for seismic data interpretation for lateral continuity of reflection events and sequence boundaries. Hilbert transform, which produces 90 o phase shift in the signal is generally used to interpret post-stack seismic data by generating analytic signal 37 . Figure 5 is the instantaneous phase attribute plot, which nicely depicts how and in which direction beds are dipping and getting pinched out towards the sea bottom slope. Figure 6 shows the Hilbert transform of the inline and crossline profile, which clearly delineates various subsurface geological features. It is observed that the reflection strength and instantaneous frequency plots (Figs. 3 – 4 ) are illustrating hydrocarbon depositional features like gas hydrate and free gas and their distribution patterns and pathways. Whereas, instantaneous phase and Hilbert transform plots (Figs. 5 – 6 ) are illustrating the bed boundaries and discontinuities like slipped-sediment, decollement, the base of debris flow and deformed sediments, pinch outs, and strong part of the BSR. From Figs. 5 and 6 , it is observed that the different upward dipping strata (right to left) are slowly becoming horizontal and then dipping downward along the seafloor dip, and further pinching out to the seafloor. Dipping downward and getting pinched out may be due to the sliding of upper sediment mass (debris). The average concentration of gas hydrate in this area is estimated to be low 8 , because gas from dissociated gas hydrate and free gases below the gas hydrate layers are migrating up through several paths (Figs. 3 , 4 ), and maybe triggering the slope failure. Our results of seismic attribute analysis reveal details of various subsurface features in the northern Hikurangi margin, which is a unique place of having tectonic activity, mass transport deposit, slope failure, sediment deformation, fractures, fluid migration pathways and gas hydrate deposit on the shallowest subduction zone on Earth. Conclusions In this study, we analyze four seismic attributes such as reflection strength, instantaneous frequency, instantaneous phase and Hilbert transform to interpret various subsurface features in the Tuaheni Landslide Complex on the upper slope of the northern Hikurangi margin, New Zealand. The northern Hikurangi margin is a very interesting and important place for research, where tectonic activity, mass transport deposit, slope failure, sediment deformation, fractures, fluid migration pathways, gas hydrate deposit, link of gas hydrate dissociation on tectonic activity and vice-versa are observed on the shallowest subduction zone on the Earth. We successfully identify these subsurface features on the seismic attribute plots, which are not visible on the seismic data. Declarations Acknowledgments We are thankful to the Directors, Banaras Hindu University, Varanasi and the CSIR-National Geophysical Research Institute, Hyderabad, for their kind permission to publish the work. The authors are thankful to IODP Expedition 372/375 scientists and other participants. The IODP India, NCPOR, Goa under the Ministry of Earth Science (MoES), New Delhi are dully acknowledged for allowing Uma Shankar to participate in IODP Expedition 372/375. Uma Shankar is grateful to the NCPOR, Goa for providing a grant under the project sanction number NCAOR/ IODP/20.25/201(4). The collection and processing of the P-Cable 3D volume which the seismic lines in this paper are extracted from was jointly funded by the New Zealand Ministry for Business Innovation and Employment (MBIE), NIWA and GNS Science Core funding and the Deutsche Forschungsgemeinschaft (DFG-Grant BI 404/7|KR 2222/18). This research used data and samples provided by the International Ocean Discovery Program (IODP). Data availability All data generated or analysed during this study are included in this published article [and its supplementary information files]. References Barnes, P. M., Nicol, A. & Harrison, T. Late Cenozoic evolution and earthquake potential of an active listric thrust complex above the Hikurangi subduction zone, New Zealand. GSA Bulletin 114 (11), 1379–1405 (2002). Barnes, P. M., et al. Tectonic and geological framework for gas hydrates and cold seeps on the Hikurangi subduction margin, New Zealand. Mar. Geol. 272 , 26–48 (2010). Greinert, J. et al. Methane seepage along the Hikurangi Margin, New Zealand: Overview of studies in 2006 and 2007 and new evidence from visual, bathymetric and hydroacoustic investigations. Mar. Geol. 272 , 6–25 (2010). Pecher, I. A., Barnes, P. M., LeVay, L. J. & the Expedition 372 Scientists. Expedition 372 Preliminary Report: Creeping Gas Hydrate Slides and Hikurangi LWD. International Ocean Discovery Program. https://doi.org/10.14379/iodp.pr.372.2018 (2018). Pecher, I. A., Henrys, S. A., Ellis, S., Chiswell, S. M. & Kukowski, N. Erosion of the seafloor at the top of the gas hydrate stability zone on the Hikurangi Margin, New Zealand. Geophys. Res. Lett. 32 (24), L24603 (2011). Pecher, I. A. et al. Focussing of fluid expulsion on the Hikurangi margin, New Zealand, based on evidence for free gas in the regional gas hydrate stability zone. Mar. Geol., 272 , 99–113 (2010). Gross, F. et al. Free gas distribution and basal shear zone development in a subaqueous landslide – Insight from 3D seismic imaging of the Tuaheni Landslide Complex, New Zealand. Earth and Planetary Science Letters 502 , 231–243 (2018). Shankar, U., Ojha, M. & Ghosh, R. Assessment of gas hydrate reservoir from inverted seismic impedance and porosity in the northern Hikurangi margin, New Zealand. Mar. Petro. Geo. 123 , 104751 (2021). Crutchley, G. J. et al. Investigating the basal shear zone of the submarine Tuaheni Landslide Complex, New Zealand: A core-log-seismic integration study. J. Geophy. Res. Solid Earth 127 , e2021JB021997 (2022). Kim, K. J., Yi, B. Y., Kang, N. K. & Yoo, D. G. Seismic Attribute Analysis of the Indicator for Gas Hydrate Occurrence in the Northwest Ulleung Basin, East Sea. Energy Procedia 76 , 463–469 (2015). Shankar, U., Sain, K. & Riedel, M. Assessment of gas hydrate stability zone and geothermal modelling of BSR in the Andaman Sea. J. Asian Earth Sci. 79 , 358–365 (2014). Wang, X. et al. Geophysical signatures associated with fluid flow and gas hydrate occurrence in a tectonically quiescent sequence, Qiongdongnan Basin, South China Sea. Geofluids 10 , 351–368 (2010). Wang, X., Wu, S., Guo, Y., Yang, S. & Gong, Y. Geophysical Indicators of Gas Hydrate in the Northern Continental Margin, South China Sea. J. Geol. Res. Special volume 2011 , 1–8 (2011). doi: 10.1155/2011/359597 . Horozal, S.et al. Seismic indicators of gas hydrate and associated gas in the Ulleung Basin, East Sea (Japan Sea) and implications of heat flows derived from depths of the bottom-simulating reflector. Mar. Geol. 258 (1–4), 126–138 (2009). Ojha, M. & Sain, K. Seismic attributes for identifying gas-hydrates and free-gas zones: application to the Makran accretionary prism. Episodes 32 (4), 264–270 (2009). Hato, M., Matsuoka, T., Inamori, T. & Saeki, T. Detection of methane-hydrate-bearing zones using seismic attributes analysis. The Leading Edge 25 , 607–609 (2006). Bellefleur, G., Riedel, M. & Brent, T. Seismic characterization and continuity analysis of gas-hydrate horizons near Mallik research wells, Mackenzie Delta, Canada. The Leading Edge 25 , 599–604 (2006). Chopra, S. & Marfurt, K. J. Seismic attributes–A historical perspective. Geophysics 70 , 3SO–28SO (2004). Berndt, C., Bunz, S., Clayton, T., Mienert, J. & Saunders, M. Seismic character of bottom simulating reflectors: examples from the mid-Norwegian margin. Mar. Petrol. Geol. 21 , 723–733 (2004). Barnes et. al. Expedition 372A summary. IODP proceedings (2019). https://doi.org/10.14379/iodp.proc.372A.101. 2019. Wood, W. T. & Ruppel L, C. Seismic investigations of the Blake ridge gas hydrate area: a synthesis. In Paull, C. K., Matsumoto, R., Wallace, P. J., and Dillon, W. P. (Eds.). Proceedings of the Ocean Drilling Program, Scientific Results 164 , 253–264 (2000). Taner, M. T., Koehler, F. & Sheriff, R. E. Complex trace analysis. Geophysics 44 , 1041–1063 (1979). Lee, M. W. & Dillon, W. P. Amplitude blanking related to the pore-filling of gas hydrate in sediments. Mar. Geophy. Res. 22 , 101–109 (2001). Taylor, M. H., Dillon, W. P. & Pecher, I. A. Trapping and migration of methane associated with the gas hydrate stability zone at the Blake Ridge Diapir: new insights from seismic data. Mar. Geol. 164 , 79–89 (2000). Beavan, J., Ellis, S., Wallace, L. & Denys, P. H. Kinematic Constraints from GPS on Oblique Convergence of the Pacific and Australian Plates, Central South Island, New Zealand. Geophysical Monograph Series 175 , 75–94 (2007). Mountjoy, J. J. et al. Shallow methane hydrate system controls ongoing, downslope sediment transport in a low-velocity active submarine landslide complex, Hikurangi Margin, New Zealand. Geochem. Geophys. Geosyst. 15 , 1525–2027 (2014). Mountjoy, J. J. & Barnes, P. M. Active upper plate thrust faulting in regions of low plate interface coupling, repeated slow slip events, and coastal uplift: Example from the Hikurangi Margin, New Zealand. Geochem. Geophys. Geosyst. 12 , Q01005 (2011). Lewis K. B. & Barnes, P. M. Kaikoura Canyon, New Zealand: active conduit from near-shore sediment zones to trench-axis channel. Mar. Geol. 162 (1), 39–69 (1999). Pecher, I. A., Henrys, S. A., Ellis, S., Chiswell, S. M. & Kukowski, N. Erosion of the seafloor at the top of the gas hydrate stability zone on the Hikurangi Margin, New Zealand. Geophys. Res. Lett. 32 (24), L24603 (2005). Wood, R. & Davy, B. The Hikurangi Plateau. Mar. Geol. 118 , 153–173 (1994). Lewis, K. B. & Pettinga, J. R. The emerging, imbricate frontal wedge of the Hikurangi Margin. In: Ballance, P. F. (Ed.), South Pacifc Sedimentary Basins. Sedimentary Basins of the World 3. Elsevier, 225–250 (1993). Robertson, J. D. & Nogami, H. H. Complex seismic trace analysis of thin beds. Geophysics 49 , 344–352 (1984). Robertson, J. D. & Fisher, D. A. Complex seismic trace attributes. The Leading Edge 7 , 22–26 (1998). White, R. E. Properties of instantaneous seismic attributes. The Leading Edge 10 , 26–32 (1991). Barnes, A. E. A tutorial on complex seismic trace analysis. Geophysics 72 (6), W33 (2007). Taner, M. T. & Sheriff, R. E. Application of Amplitude, Frequency, and Other Attributes to Stratigraphic and Hydrocarbon Determination: Section 2. Application of Seismic Reflection Configuration to Stratigraphic Interpretation. Seismic Stratigraphy - Applications to Hydrocarbon Exploration. AAPG memoir, 301–327 (1977). Purves, S. Phase and the Hilbert transform. The Leading Edge 33 , 1164–1166 (2014). Additional Declarations No competing interests reported. Supplementary Files Supplement.docx Cite Share Download PDF Status: Posted Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-2045866","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":142234366,"identity":"7f6ba540-c868-4986-a363-b3c1aea201fa","order_by":0,"name":"Uma Shankar","email":"","orcid":"","institution":"Banaras Hindu University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Uma","middleName":"","lastName":"Shankar","suffix":""},{"id":142234367,"identity":"4ca72252-68ca-441b-ba75-7381b3603b4d","order_by":1,"name":"Maheswar Ojha","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABB0lEQVRIiWNgGAWjYFACHjgrjYGhAkgxo4vj13KGRC1sDIxtRDhLt/3swYc/2+zyGdgbnj34Oe+O3fZ2BrYPH/4wyJjj0GJ2Ji/ZmLct2bKB50C6Ye+2Z8lzDjMwz5zZxsBj2YBDy4EcM2nGbcwGDBIJaRK82w4nSzAzMDPzNjDwGBzAoeX8G/OfP7fVg7VI/p0D1fLnDx4tN3LMGICGg7VI8zYctgNrAQYFHi1vjKV5/x03YOA5kCYtc+xwggQzYzNjb5sEHoflGH78cabagIG9J03yTc1hewn+w4cZfvyxscelBQ7sD/AkgOjEBgbGBiAtQUA9GLCDTbUnRukoGAWjYBSMLAAAoVBTfEpXuE4AAAAASUVORK5CYII=","orcid":"","institution":"CSIR-National Geophysical Research Institute","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Maheswar","middleName":"","lastName":"Ojha","suffix":""},{"id":142234368,"identity":"ee1b4e9b-dd1a-46b8-ad20-a2a6b6f65724","order_by":2,"name":"Ranjana Ghosh","email":"","orcid":"","institution":"CSIR-National Geophysical Research Institute","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Ranjana","middleName":"","lastName":"Ghosh","suffix":""}],"badges":[],"createdAt":"2022-09-08 14:59:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2045866/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2045866/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":27633506,"identity":"6b540168-aa29-40a2-8f97-4c4397961cc4","added_by":"auto","created_at":"2022-10-11 17:50:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":279513,"visible":true,"origin":"","legend":"\u003cp\u003eTwo seismic lines (red) crossing the drilling Site U1517 (black circle) of IODP expedition 372 in the Tuaheni Landslide Complex on the upper slope of the northern Hikurangi margin. The inset shows the tectonic setup of the northern Hikurangi margin, New Zealand. The color scale shows the bathymetry of the study area (blue square).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-2045866/v1/06f17ccbf0b6f38357da73c7.png"},{"id":27633740,"identity":"27db9620-17db-42f4-a50a-9798e49aa110","added_by":"auto","created_at":"2022-10-11 17:55:26","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1374483,"visible":true,"origin":"","legend":"\u003cp\u003e(a) In-line and (b) cross-line seismic section. Seafloor, BSR, decollement of sediment slide and base of the debris deposit are shown with arrows on seismic sections in the Tuaheni Landslide Complex on the upper slope of the northern Hikurangi margin, New Zealand. Sonic P-wave impedance is superimposed on seismic sections.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-2045866/v1/aba7084a690e476309371ac4.png"},{"id":27633509,"identity":"4d9e740b-31ca-40eb-96d2-8f42d0831898","added_by":"auto","created_at":"2022-10-11 17:50:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2595481,"visible":true,"origin":"","legend":"\u003cp\u003eReflection strength plots along in-line (top panel) and cross-line (bottom panel) show loss of amplitude above the BSR and the enhanced reflection across gas-charged sediments below BSR. The seafloor, BSR, decollement, slipped sediment, the base of debris flow and deformed sediment, etc. are marked with dashed lines and arrows.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-2045866/v1/4c371819a1b2c52e41fa2793.png"},{"id":27633741,"identity":"50e3f7f1-6f11-4cfc-a8f3-fee406870bb3","added_by":"auto","created_at":"2022-10-11 17:55:26","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2603566,"visible":true,"origin":"","legend":"\u003cp\u003eInstantaneous frequency plots along In-line (top panel) and cross-line (bottom panel) show low-frequency shadows due to the presence of free gas. The seafloor, BSR, decollement, slipped sediment, the base of debris flow and deformed sediment, gas migration and velocity pulled down, etc. are marked with dashed lines and arrows.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-2045866/v1/1adfa0316eaaf5f61de1d75b.png"},{"id":27633743,"identity":"d4893de0-3507-46ff-b6a0-eef6e9900b16","added_by":"auto","created_at":"2022-10-11 17:55:26","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2676191,"visible":true,"origin":"","legend":"\u003cp\u003eInstantaneous phase plots along in-line (top panel) and cross-line (bottom panel) profiles show the structure of bedding planes. The seafloor, BSR, decollement, slipped sediment, the base of debris flow and deformed sediment, and pinching outs, etc. are marked with dashed lines and arrows.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-2045866/v1/7294a28684cd573bb986fb7a.png"},{"id":27633512,"identity":"7698ed20-323c-4fb3-9088-17383c800319","added_by":"auto","created_at":"2022-10-11 17:50:26","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":2906967,"visible":true,"origin":"","legend":"\u003cp\u003eHilbert transform plots along in-line (top panel) and cross-line (bottom panel) seismic profiles show the geophysical signatures of different subsurface features. The seafloor, BSR, decollement, slipped sediment, the base of debris flow and deformed sediment, and pinching outs, etc. are marked with dashed lines and arrows.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-2045866/v1/78945a69e74bdc14141f843d.png"},{"id":28437087,"identity":"e6d93335-cb30-44a9-8d7a-94afe64e9cbf","added_by":"auto","created_at":"2022-10-31 06:14:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":11445726,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2045866/v1/22056098-ff11-479a-8d30-b1a1931a8832.pdf"},{"id":27633742,"identity":"c0fef5aa-dd78-4b80-9b1b-1f04abb6c970","added_by":"auto","created_at":"2022-10-11 17:55:26","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":11214,"visible":true,"origin":"","legend":"","description":"","filename":"Supplement.docx","url":"https://assets-eu.researchsquare.com/files/rs-2045866/v1/945cb86f81f0ae43631c9bf7.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Subsurface structures of the Tuaheni Landslide Complex at the upper slope of the northern Hikurangi margin, New Zealand, revealed by seismic attribute analysis","fulltext":[{"header":"Introduction","content":"One of the seismically active areas on the Earth is the northern Hikurangi margin, where the presence of gas hydrates, fluid migration, cold seeps, and creep-like deformation is thought to be responsible for frequent earthquakes, slow slip events, submarine landslides causing Tsunami, and high tides1,2,3,4,5,6 . The presence of gas hydrate in the Tuaheni Landslide Complex (TLC) on the upper slope of the northern Hikurangi margin (Fig. 1) has been inferred by identifying discontinuous bottom simulating reflectors (BSR) on the multi-channel seismic volume7,8,9,4,5,6,1,2,3. However, the BSR is not completely following the topography of the seafloor and is rapidly wrapping upward (Fig. 2), which may be caused by regional thermal anomalies, cold seeps, and fluid migration2,3,6. Various seismic attributes like reflection strength, instantaneous frequency, instantaneous phase and Hilbert transform are very useful to interpret various subsurface features, which are not always possible to see directly from the seismic section. The presence of gas-hydrates and free-gas changes the sediment properties in various ways, which have been characterized by various seismic attributes like reflection strength and instantaneous frequency in various world margins such as Blake Ridge, Vring Plateau off Norway, Indian offshore, Shenhu area of South China sea, Makran Accretionary Prism, Ulleung Basin offshore South Korea etc10,11,12,13,14,15,16,17,18,19,20,21,22. Gas hydrates in sediment pore spaces reduce the sediment porosity and thus seismic impedance contrasts between units within gas hydrate-bearing sediments, resulting in lower seismic reflection amplitudes and making the seismic section transparent23. Sediment velocity is increased by the presence of gas hydrates, while free gas in the pore spaces beneath the BSR greatly reduces seismic velocity, changing the impedance contrasts across the BSR15. On the other hand, gas-charged sediments absorb lots of seismic energy and show low-frequency dominance in the instantaneous frequency section24.\nDuring the recent drilling at Site U1517 under the International Ocean Drilling Program (IODP) Expedition 372 in 2018, gas hydrate-bearing reservoirs were documented up to 160m below the seafloor and at water depths between 600 and 1000 m4. In this study, we interpret reflection strength, instantaneous frequency, instantaneous phase and Hilbert transform of an in-line and a cross-line multi-channel seismic section crossing the well location in the northern Hikurangi margin to identify and analyse various subsurface structures/features associated with the presence of gas hydrate, free gas, fluid migration pathways, sediments slides, tectonic activity etc.\n"},{"header":"Study Area And Data","content":"\u003cp\u003eThe Hikurangi margin is located off the East Coast of the North Island of New Zealand. It is characterized by the subduction of the Pacific Plate beneath the Australian Plate (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The plate convergence occurs obliquely towards the SW\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. The oblique convergence separates subduction thrust, and margin normal and parallel components. The Hikurangi margin is further influenced by mass transport deposits and the subduction of various seamounts on the oceanic plate\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. The northern Hikurangi margin includes numerous seamounts on the subducting Pacific plate and is categorized by a combination of tectonic erosion in the north and limited accretion developed further south\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. At the northern Hikurangi margin, the Pacific plate subducts beneath the Australian plate (eastern North Island, New Zealand) at a rate of 4.5\u0026ndash;5.5 cm/year\u003csup\u003e4\u003c/sup\u003e as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The oceanic subducting plate comprises the Hikurangi Plateau, a rough-crust, seamount-studded large igneous province of Cretaceous age (120\u0026ndash;90 Ma), which is part of ~\u0026thinsp;600 km long off eastern North Island\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Hikurangi Margin marks the boundary between the obliquely convergent Pacific plate and Australian plate and the portion where the oceanic crust of the Pacific Plate subducts beneath the continental crust of the Australian Plate and New Zealand North Island\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Geophysical data modeling of the Hikurangi plateau shows the oceanic plate is subducted beneath the northern Island\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. The stratigraphy and structure of the Hikurangi margin contain pre-subduction and Neogene subduction systems\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. The geology comprises an imbricated accretionary wedge. The wedge consists of three major stratigraphic groups: an inner foundation of pre-subduction rocks consisting of late Cretaceous and Paleogene rocks, an outer wedge of Pliocene to Pleistocene accreted trench-filled turbidites, and a deforming cover sequence of Miocene to the recent shelf and slope basin sediments\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. Barnes et al.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e observed numerous deformed rocks on seismic images, which could be associated with active thrust faulting and folding in Miocene. The IODP 372 expedition discovered five major litho-units at Site U1517: i) the top four meters below the seafloor with silty-clay and clayey-silt layer, ii) 4\u0026ndash;40 meters below seafloor (mbsf) with alternate sand and mud layers, iii) 40\u0026ndash;67 mbsf with alternate silt and clay layers, iv) 67\u0026ndash;103 mbsf with silty-clay and clayey-silt, and v) 103\u0026ndash;187 mbsf as a mixture of above four units\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. Later, seven litho-units were observed along seismic profiles based on the acoustic impedance and porosity inversion\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn this study, seismic data from a 3D seismic volume were extracted for scientific investigation purposes in the northern Hikurangi margin of New Zealand\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Seismic data has a high-frequency content of about 220 Hz, with a dominant frequency of about 90 Hz. The seismic data sets were used for site selection and drilling targets for the IODP 372 Expedition before gas hydrate exploration. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e depicts an in-line seismic section oriented along NW-SE and a cross-line seismic section oriented along SW-NE crossing Site U1517 drilled at 720 m water depth\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. The drilling site is located within the 3D seismic survey area in the Tuaheni landslide complex, where logging while drilling (LWD) and wire-line loggings (WL) were performed. Mainly, resistivity and velocity logs were used to identify and estimation of gas hydrate in the study area. The seismic sections (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) reveal distinct BSRs in the steep slope region, followed by a high reflectivity zone at and below the base of the gas hydrate stability zone (BGHSZ) with the decollement of landslide and the base of debris flow\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003eSeismic Attributes\u003c/h3\u003e\n\u003cp\u003eSeismic attributes are some information extracted from the seismic data to enhance the subsurface geological features. Instantaneous amplitude and instantaneous phase are the two fundamental seismic attributes used in complex seismic trace analysis. Many attributes are derived from these two main attributes - amplitude and phase, through differentiation, averaging, combination, or transformation. Instantaneous attributes are defined at every point on the seismic trace. Since the seismic trace is insufficient to separate instantaneous amplitude and phase, the quadrature trace is first calculated from the seismic trace using the Hilbert transform. The colour displays of seismic attributes are used for the interpretation of geologic structures, stratigraphy, and rock/pore fluid properties. The instantaneous amplitude or trace envelope is a measure of brightness or reflection strength and it is independent of phase and polarity. It is sensitive to changes in acoustic impedance, thus to lithology, porosity, hydrocarbons and thin-bed tuning\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. The presence of gas hydrate increases the acoustic impedance, whereas, the presence of even a small amount of free gas decreases the acoustic impedance. The instantaneous phase is used to track reflector continuity to detect unconformities, faults and lateral changes in stratigraphy when the phase angle cannot be followed from trace to trace\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Instantaneous frequency can be used to identify abnormal attenuation\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e and thin bed tuning\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Since many reflector events are a composite of individual reflections from closely spaced reflectors or tuning of multiple impedance contrasts, a characteristic reflection frequency pattern is produced. This character of a composite reflection changes gradually as the sequence changes laterally in thickness or lithology. Another useful application of instantaneous frequency is to identify sediments that give seismic attenuation, such as gas sands because they highly attenuate seismic P waves by absorbing high-frequency content and therefore low-frequency shadows are observed. Gas hydrates also appear to attenuate energy as discussed above, but not as much as gas-bearing sediments\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eMost attributes have a noisy character since they are derived through differentiation, which introduces less coherent high frequencies and suppresses more coherent low frequencies. Also, because the instantaneous amplitude and phase have inflection points and discontinuities, their differentiation results in spurious spikes. The instantaneous attributes are also spiky and noisy because of the noise in the data. The most anomalous values of instantaneous frequency are most often associated with small amplitudes and are the least reliable, whereas the ones associated with larger amplitudes are more stable\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. To remove the high-frequency noise and spikes to ease interpretation by emphasizing the frequency of stronger reflectors, the instantaneous attributes are filtered. The most common filters are the median filtering, which is the selection of instantaneous attributes at envelope peaks and weighted averaging by the instantaneous power or envelope squared\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe conventional seismic trace \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(x\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003e can be represented as the real component of a complex seismic trace \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(z\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003e. The imaginary component \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(y\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003e is called the quadrature trace as given below,\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$z\\left(t\\right)=x\\left(t\\right)+i.y\\left(t\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e.\u003c/p\u003e \u003cp\u003eThe quadrature trace is determined from \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(x\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003e by convolution in the time domain using the Hilbert transform quadrature filter \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(h\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003e, such that,\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$y\\left(t\\right)=h\\left(t\\right)*x\\left(t\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e,\u003c/p\u003e \u003cp\u003ewhere,\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$h\\left(t\\right)=1/\\left(\\pi t\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe Fourier transform of \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(h\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003eis defined as,\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$H\\left(f\\right)=\\left\\{\\begin{array}{c}-i, f\u0026gt;0\\\\ +i, f\u0026lt; 0\\\\ 0, f= 0\\end{array}\\right.$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e,\u003c/p\u003e \u003cp\u003ewhere, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(f\\)\u003c/span\u003e\u003c/span\u003e is frequency. A phase rotator \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(p(t,\\varphi )\\)\u003c/span\u003e\u003c/span\u003e that subtracts an angle \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varphi\\)\u003c/span\u003e\u003c/span\u003e is given by,\u003cdiv id=\"Equ5\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ5\" name=\"EquationSource\"\u003e\n$$p\\left(t,\\varphi \\right)=\\delta \\left(t\\right)cos\\varphi +h\\left(t\\right)sin\\varphi ,$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\delta\\)\u003c/span\u003e\u003c/span\u003e is the delta function. When applying the phase rotator to a seismic trace \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(x\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003e and using Eq.\u0026nbsp;\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the trace is rotated as,\u003cdiv id=\"Equ6\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ6\" name=\"EquationSource\"\u003e\n$$x\\overline{\\left(t\\right)}=p(t,\\varphi )*x\\left(t\\right)=x\\left(t\\right)cos\\varphi +y\\left(t\\right)sin\\varphi$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e6\u003c/div\u003e\u003c/div\u003e.\u003c/p\u003e \u003cp\u003eThe rotated trace under a phase rotation of 90\u003csup\u003eo\u003c/sup\u003e is the Hilbert transform (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(x\\overline{\\left(t\\right))}=y\\left(t\\right),\\)\u003c/span\u003e\u003c/span\u003e resulting in a quadrature trace\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. The quadrature trace does not have any physical meaning. Peaks and troughs on the quadrature trace correspond to zero crossing on the seismic trace\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. The trace envelope \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(a\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003eis defined as the maximum value that a seismic trace can have under a constant phase rotation, which makes it independent of phase. The trace envelope can be described as a function that connects the waveform peaks, as well as troughs since it is independent of polarity.\u003c/p\u003e \u003cp\u003eIf \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varphi \\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003e represents the angle that maximizes the value of the rotated trace, Eq.\u0026nbsp;\u003cspan refid=\"Equ6\" class=\"InternalRef\"\u003e6\u003c/span\u003e can be written as,\u003cdiv id=\"Equ7\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ7\" name=\"EquationSource\"\u003e\n$$a\\left(t\\right)=x\\left(t\\right)cos\\varphi \\left(t\\right)+y\\left(t\\right)sin\\varphi \\left(t\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e7\u003c/div\u003e\u003c/div\u003e.\u003c/p\u003e \u003cp\u003eEquation \u003cspan refid=\"Equ7\" class=\"InternalRef\"\u003e7\u003c/span\u003e is equivalent to\u003cdiv id=\"Equ8\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ8\" name=\"EquationSource\"\u003e\n$$\\frac{\\delta a\\left(t\\right)}{\\delta \\varphi \\left(t\\right)}=0=-x\\left(t\\right)sin\\varphi \\left(t\\right)+y\\left(t\\right)cos\\varphi \\left(t\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e8\u003c/div\u003e\u003c/div\u003e.\u003c/p\u003e \u003cp\u003eBecause when the trace envelope equals the rotated seismic trace (at maximum), its change with respect to the rotation angle is zero. The trace envelope derives from equations \u003cspan refid=\"Equ7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Equ8\" class=\"InternalRef\"\u003e8\u003c/span\u003e as,\u003cdiv id=\"Equ9\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ9\" name=\"EquationSource\"\u003e\n$$a\\left(t\\right)={{(x}^{2}\\left(t\\right)+{y}^{2}\\left(t\\right))}^{0.5}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e9\u003c/div\u003e\u003c/div\u003e.\u003c/p\u003e \u003cp\u003eThe angle (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\varphi\\)\u003c/span\u003e\u003c/span\u003e) that rotates the trace to a maximum, or instantaneous phase is derived from Eq.\u0026nbsp;\u003cspan refid=\"Equ8\" class=\"InternalRef\"\u003e8\u003c/span\u003e as,\u003cdiv id=\"Equ10\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ10\" name=\"EquationSource\"\u003e\n$$\\varphi =arctan\\frac{y\\left(t\\right)}{x\\left(t\\right)}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e10\u003c/div\u003e\u003c/div\u003e.\u003c/p\u003e \u003cp\u003eThe instantaneous phase has a saw tooth appearance and its values range from (-π, π). They refer to the apparent position along the seismic trace, such that peaks have 0\u003csup\u003eo\u003c/sup\u003e phase, trough has 180\u003csup\u003eo\u003c/sup\u003e phase, and downward zero crossing has \u0026minus;\u0026thinsp;90\u003csup\u003eo\u003c/sup\u003e phase. If the seismic trace is represented by a cosine wave with amplitude \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(a\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003e, the quadrature trace is a sine wave with the same amplitude. A complex-valued signal from Eq.\u0026nbsp;\u003cspan refid=\"Equ7\" class=\"InternalRef\"\u003e7\u003c/span\u003e can be written as,\u003cdiv id=\"Equ11\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ11\" name=\"EquationSource\"\u003e\n$$z\\left(t\\right)=a\\left(t\\right)\\text{e}\\text{x}\\text{p}\\left(i\\varphi \\left(t\\right)\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e11\u003c/div\u003e\u003c/div\u003e.\u003c/p\u003e \u003cp\u003eThe instantaneous frequency represents the rate of change with the time of the instantaneous phase divided by 2π\u003csup\u003e22\u003c/sup\u003e,\u003cdiv id=\"Equ12\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ12\" name=\"EquationSource\"\u003e\n$$f\\left(t\\right)=\\frac{1}{2{\\pi }}\\frac{d\\varphi }{dt}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e12\u003c/div\u003e\u003c/div\u003e,\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(f\\left(t\\right)\\)\u003c/span\u003e \u003c/span\u003e has units of Hz, but it is not a frequency in the physical sense, as it has negative values at inflection points of the trace and can also exceed the maximum frequency in the signal when the trace is close to zero and crosses it for one or two samples.\u003c/p\u003e"},{"header":"Results And Discussion","content":"\u003cp\u003eFour seismic attributes namely reflection strength, instantaneous frequency, instantaneous phase and Hilbert transform calculated along the in-line and cross-line profiles. These attributes are clearly illustrating various subsurface features like slipped sediment, decollement, the base of debris flow and deformed sediments, pinch outs, BSR, gas-charged sediments, gas migration etc. in the Tuaheni Landslide Complex on the upper slope of the northern Hikurangi margin, New Zealand. All interpretations are dawn based on four seismic attributes, where some features are visible on some attributes and others are on other attributes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eReflection strength plots along two seismic lines (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) show various features demarcated by the contrast between low and high reflection strength. BSR is clearly illustrated by the very high reflection strength of underlying gas-charged sediments. The base of the slipped sediment, debris and deformed sediments and decollement, which are in generally water-filled zones are demarcated by low reflection strength lineaments. Slipped sediment is not there on the cross line. Scattered high reflection strengths are observed in the debris flow and deformed sediments within the hydrate stability zone, which is possibly because of the dissociation of gas hydrate due to the tectonic activity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe instantaneous frequency plot generally depicts the presence of gas as low-frequency shadow as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. Presence of free gas within the sediments, below the BSR, upward movement of free gas, and velocity pulled down because of lowering velocity due to gas are clearly observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. This interpretation is consistent with observations from the Blake Ridge\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, the Vring Plateau off Norway\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e, the Makran accretionary prism\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e, the Ulleung basin\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, and the South China Sea\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe instantaneous phase attribute is independent of the amplitude used for seismic data interpretation for lateral continuity of reflection events and sequence boundaries. Hilbert transform, which produces 90\u003csup\u003eo\u003c/sup\u003e phase shift in the signal is generally used to interpret post-stack seismic data by generating analytic signal\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e is the instantaneous phase attribute plot, which nicely depicts how and in which direction beds are dipping and getting pinched out towards the sea bottom slope. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the Hilbert transform of the inline and crossline profile, which clearly delineates various subsurface geological features. It is observed that the reflection strength and instantaneous frequency plots (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) are illustrating hydrocarbon depositional features like gas hydrate and free gas and their distribution patterns and pathways. Whereas, instantaneous phase and Hilbert transform plots (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) are illustrating the bed boundaries and discontinuities like slipped-sediment, decollement, the base of debris flow and deformed sediments, pinch outs, and strong part of the BSR. From Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, it is observed that the different upward dipping strata (right to left) are slowly becoming horizontal and then dipping downward along the seafloor dip, and further pinching out to the seafloor. Dipping downward and getting pinched out may be due to the sliding of upper sediment mass (debris). The average concentration of gas hydrate in this area is estimated to be low\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e, because gas from dissociated gas hydrate and free gases below the gas hydrate layers are migrating up through several paths (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), and maybe triggering the slope failure. Our results of seismic attribute analysis reveal details of various subsurface features in the northern Hikurangi margin, which is a unique place of having tectonic activity, mass transport deposit, slope failure, sediment deformation, fractures, fluid migration pathways and gas hydrate deposit on the shallowest subduction zone on Earth.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn this study, we analyze four seismic attributes such as reflection strength, instantaneous frequency, instantaneous phase and Hilbert transform to interpret various subsurface features in the Tuaheni Landslide Complex on the upper slope of the northern Hikurangi margin, New Zealand. The northern Hikurangi margin is a very interesting and important place for research, where tectonic activity, mass transport deposit, slope failure, sediment deformation, fractures, fluid migration pathways, gas hydrate deposit, link of gas hydrate dissociation on tectonic activity and vice-versa are observed on the shallowest subduction zone on the Earth. We successfully identify these subsurface features on the seismic attribute plots, which are not visible on the seismic data.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe are thankful to the Directors, Banaras Hindu University, Varanasi and the CSIR-National Geophysical Research Institute, Hyderabad, for their kind permission to publish the work. The authors are thankful to IODP Expedition 372/375 scientists and other participants. The IODP India, NCPOR, Goa under the Ministry of Earth Science (MoES), New Delhi are dully acknowledged for allowing Uma Shankar to participate in IODP Expedition 372/375. Uma Shankar is grateful to the NCPOR, Goa for providing a grant under the project sanction number NCAOR/ IODP/20.25/201(4). The collection and processing of the P-Cable 3D volume which the seismic lines in this paper are extracted from was jointly funded by the New Zealand Ministry for Business Innovation and Employment (MBIE), NIWA and GNS Science Core funding and the Deutsche Forschungsgemeinschaft (DFG-Grant BI 404/7|KR 2222/18).\u0026nbsp;This research used data and samples provided by the International Ocean Discovery Program (IODP).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article [and its supplementary information files].\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBarnes, P. M., Nicol, A. \u0026amp; Harrison, T. Late Cenozoic evolution and earthquake potential of an active listric thrust complex above the Hikurangi subduction zone, New Zealand. GSA Bulletin \u003cb\u003e114\u003c/b\u003e (11), 1379\u0026ndash;1405 (2002).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarnes, P. M., et al. Tectonic and geological framework for gas hydrates and cold seeps on the Hikurangi subduction margin, New Zealand. Mar. Geol. \u003cb\u003e272\u003c/b\u003e, 26\u0026ndash;48 (2010).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGreinert, J. et al. Methane seepage along the Hikurangi Margin, New Zealand: Overview of studies in 2006 and 2007 and new evidence from visual, bathymetric and hydroacoustic investigations. Mar. Geol. \u003cb\u003e272\u003c/b\u003e, 6\u0026ndash;25 (2010).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePecher, I. A., Barnes, P. M., LeVay, L. J. \u0026amp; the Expedition 372 Scientists. Expedition 372 Preliminary Report: Creeping Gas Hydrate Slides and Hikurangi LWD. International Ocean Discovery Program. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.14379/iodp.pr.372.2018\u003c/span\u003e\u003cspan address=\"10.14379/iodp.pr.372.2018\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePecher, I. A., Henrys, S. A., Ellis, S., Chiswell, S. M. \u0026amp; Kukowski, N. Erosion of the seafloor at the top of the gas hydrate stability zone on the Hikurangi Margin, New Zealand. Geophys. Res. Lett. \u003cb\u003e32\u003c/b\u003e (24), L24603 (2011).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePecher, I. A. et al. Focussing of fluid expulsion on the Hikurangi margin, New Zealand, based on evidence for free gas in the regional gas hydrate stability zone. Mar. Geol., \u003cb\u003e272\u003c/b\u003e, 99\u0026ndash;113 (2010).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGross, F. et al. Free gas distribution and basal shear zone development in a subaqueous landslide \u0026ndash; Insight from 3D seismic imaging of the Tuaheni Landslide Complex, New Zealand. Earth and Planetary Science Letters \u003cb\u003e502\u003c/b\u003e, 231\u0026ndash;243 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShankar, U., Ojha, M. \u0026amp; Ghosh, R. Assessment of gas hydrate reservoir from inverted seismic impedance and porosity in the northern Hikurangi margin, New Zealand. Mar. Petro. Geo. \u003cb\u003e123\u003c/b\u003e, 104751 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCrutchley, G. J. et al. Investigating the basal shear zone of the submarine Tuaheni Landslide Complex, New Zealand: A core-log-seismic integration study. \u003cem\u003eJ. Geophy. Res. Solid Earth\u003c/em\u003e \u003cb\u003e127\u003c/b\u003e, e2021JB021997 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim, K. J., Yi, B. Y., Kang, N. K. \u0026amp; Yoo, D. G. Seismic Attribute Analysis of the Indicator for Gas Hydrate Occurrence in the Northwest Ulleung Basin, East Sea. Energy Procedia \u003cb\u003e76\u003c/b\u003e, 463\u0026ndash;469 (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShankar, U., Sain, K. \u0026amp; Riedel, M. Assessment of gas hydrate stability zone and geothermal modelling of BSR in the Andaman Sea. J. Asian Earth Sci. \u003cb\u003e79\u003c/b\u003e, 358\u0026ndash;365 (2014).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang, X. et al. Geophysical signatures associated with fluid flow and gas hydrate occurrence in a tectonically quiescent sequence, Qiongdongnan Basin, South China Sea. Geofluids \u003cb\u003e10\u003c/b\u003e, 351\u0026ndash;368 (2010).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang, X., Wu, S., Guo, Y., Yang, S. \u0026amp; Gong, Y. Geophysical Indicators of Gas Hydrate in the Northern Continental Margin, South China Sea. J. Geol. Res. Special \u003cem\u003evolume\u003c/em\u003e \u003cb\u003e2011\u003c/b\u003e, 1\u0026ndash;8 (2011). doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1155/2011/359597\u003c/span\u003e\u003cspan address=\"10.1155/2011/359597\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHorozal, S.et al. Seismic indicators of gas hydrate and associated gas in the Ulleung Basin, East Sea (Japan Sea) and implications of heat flows derived from depths of the bottom-simulating reflector. Mar. Geol. \u003cb\u003e258\u003c/b\u003e (1\u0026ndash;4), 126\u0026ndash;138 (2009).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOjha, M. \u0026amp; Sain, K. Seismic attributes for identifying gas-hydrates and free-gas zones: application to the Makran accretionary prism. Episodes \u003cb\u003e32\u003c/b\u003e(4), 264\u0026ndash;270 (2009).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHato, M., Matsuoka, T., Inamori, T. \u0026amp; Saeki, T. Detection of methane-hydrate-bearing zones using seismic attributes analysis. The Leading Edge \u003cb\u003e25\u003c/b\u003e, 607\u0026ndash;609 (2006).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBellefleur, G., Riedel, M. \u0026amp; Brent, T. Seismic characterization and continuity analysis of gas-hydrate horizons near Mallik research wells, Mackenzie Delta, Canada. The Leading Edge \u003cb\u003e25\u003c/b\u003e, 599\u0026ndash;604 (2006).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChopra, S. \u0026amp; Marfurt, K. J. Seismic attributes\u0026ndash;A historical perspective. Geophysics \u003cb\u003e70\u003c/b\u003e, 3SO\u0026ndash;28SO (2004).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBerndt, C., Bunz, S., Clayton, T., Mienert, J. \u0026amp; Saunders, M. Seismic character of bottom simulating reflectors: examples from the mid-Norwegian margin. Mar. Petrol. Geol. \u003cb\u003e21\u003c/b\u003e, 723\u0026ndash;733 (2004).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarnes et. al. Expedition 372A summary. \u003cem\u003eIODP proceedings\u003c/em\u003e (2019). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.14379/iodp.proc.372A.101.\u003c/span\u003e\u003cspan address=\"10.14379/iodp.proc.372A.101.\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e2019.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWood, W. T. \u0026amp; Ruppel L, C. Seismic investigations of the Blake ridge gas hydrate area: a synthesis. In Paull, C. K., Matsumoto, R., Wallace, P. J., and Dillon, W. P. (Eds.). \u003cem\u003eProceedings of the Ocean Drilling Program, Scientific Results\u003c/em\u003e \u003cb\u003e164\u003c/b\u003e, 253\u0026ndash;264 (2000).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTaner, M. T., Koehler, F. \u0026amp; Sheriff, R. E. Complex trace analysis. Geophysics \u003cb\u003e44\u003c/b\u003e, 1041\u0026ndash;1063 (1979).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee, M. W. \u0026amp; Dillon, W. P. Amplitude blanking related to the pore-filling of gas hydrate in sediments. Mar. Geophy. Res. \u003cb\u003e22\u003c/b\u003e, 101\u0026ndash;109 (2001).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTaylor, M. H., Dillon, W. P. \u0026amp; Pecher, I. A. Trapping and migration of methane associated with the gas hydrate stability zone at the Blake Ridge Diapir: new insights from seismic data. Mar. Geol. \u003cb\u003e164\u003c/b\u003e, 79\u0026ndash;89 (2000).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBeavan, J., Ellis, S., Wallace, L. \u0026amp; Denys, P. H. Kinematic Constraints from GPS on Oblique Convergence of the Pacific and Australian Plates, Central South Island, New Zealand. Geophysical Monograph Series \u003cb\u003e175\u003c/b\u003e, 75\u0026ndash;94 (2007).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMountjoy, J. J. et al. Shallow methane hydrate system controls ongoing, downslope sediment transport in a low-velocity active submarine landslide complex, Hikurangi Margin, New Zealand. Geochem. Geophys. Geosyst. \u003cb\u003e15\u003c/b\u003e, 1525\u0026ndash;2027 (2014).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMountjoy, J. J. \u0026amp; Barnes, P. M. Active upper plate thrust faulting in regions of low plate interface coupling, repeated slow slip events, and coastal uplift: Example from the Hikurangi Margin, New Zealand. Geochem. Geophys. Geosyst. \u003cb\u003e12\u003c/b\u003e, Q01005 (2011).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLewis K. B. \u0026amp; Barnes, P. M. Kaikoura Canyon, New Zealand: active conduit from near-shore sediment zones to trench-axis channel. Mar. Geol. \u003cb\u003e162\u003c/b\u003e(1), 39\u0026ndash;69 (1999).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePecher, I. A., Henrys, S. A., Ellis, S., Chiswell, S. M. \u0026amp; Kukowski, N. Erosion of the seafloor at the top of the gas hydrate stability zone on the Hikurangi Margin, New Zealand. Geophys. Res. Lett. \u003cb\u003e32\u003c/b\u003e (24), L24603 (2005).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWood, R. \u0026amp; Davy, B. The Hikurangi Plateau. Mar. Geol. \u003cb\u003e118\u003c/b\u003e, 153\u0026ndash;173 (1994).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLewis, K. B. \u0026amp; Pettinga, J. R. The emerging, imbricate frontal wedge of the Hikurangi Margin. In: Ballance, P. F. (Ed.), South Pacifc Sedimentary Basins. Sedimentary Basins of the World 3. Elsevier, 225\u0026ndash;250 (1993).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRobertson, J. D. \u0026amp; Nogami, H. H. Complex seismic trace analysis of thin beds. Geophysics \u003cb\u003e49\u003c/b\u003e, 344\u0026ndash;352 (1984).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRobertson, J. D. \u0026amp; Fisher, D. A. Complex seismic trace attributes. The Leading Edge \u003cb\u003e7\u003c/b\u003e, 22\u0026ndash;26 (1998).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWhite, R. E. Properties of instantaneous seismic attributes. The Leading Edge \u003cb\u003e10\u003c/b\u003e, 26\u0026ndash;32 (1991).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarnes, A. E. A tutorial on complex seismic trace analysis. Geophysics \u003cb\u003e72\u003c/b\u003e(6), W33 (2007).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTaner, M. T. \u0026amp; Sheriff, R. E. Application of Amplitude, Frequency, and Other Attributes to Stratigraphic and Hydrocarbon Determination: Section 2. Application of Seismic Reflection Configuration to Stratigraphic Interpretation. Seismic Stratigraphy - Applications to Hydrocarbon Exploration. AAPG memoir, 301\u0026ndash;327 (1977).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePurves, S. Phase and the Hilbert transform. The Leading Edge \u003cb\u003e33\u003c/b\u003e, 1164\u0026ndash;1166 (2014).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Seismic attributes, gas hydrate, reflection strength, instantaneous frequency, Hikurangi margin, New Zealand. IODP Expedition 372","lastPublishedDoi":"10.21203/rs.3.rs-2045866/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2045866/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTuaheni Landslide Complex, located on the upper slope of the northern Hikurangi margin in New Zealand, is a unique location to study slow slip creep-like deformation and seafloor failure, as well as their possible relationship to the presence of gas hydrate, cold seeps, and fluid migration. Based on the visual interpretation of seismic data, sometimes it is very difficult to identify various subsurface structures and tectonic features. We study certain seismic attributes namely reflection-strength, instantaneous frequency, instantaneous phase, and Hilbert Transform in the Tuaheni Landslide Complex and observe that these attributes play a very important role to identify and interpret various subsurface geological features, which are not visible in the seismic sections. These seismic attributes nicely illustrate the fluid migration pathways, the decollement of the sediment slide, the base of the debris flow, the base of the deformed sediment and gas migration, etc. along two perpendicular seismic profiles crossing the well Site U1517 of IODP Expedition 372. The possible role of tectonic activity and seafloor slope failure due to gas hydrate dissociation and vice versa are clearly visible through fluid-filled weak zones in the seismic attribute volumes.\u003c/p\u003e","manuscriptTitle":"Subsurface structures of the Tuaheni Landslide Complex at the upper slope of the northern Hikurangi margin, New Zealand, revealed by seismic attribute analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-10-11 17:50:24","doi":"10.21203/rs.3.rs-2045866/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7b10a392-bd5b-437d-8444-3a916fb3f5d7","owner":[],"postedDate":"October 11th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2022-10-31T06:14:30+00:00","versionOfRecord":[],"versionCreatedAt":"2022-10-11 17:50:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-2045866","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2045866","identity":"rs-2045866","version":["v1"]},"buildId":"FbvkV6FR0MCFSLy54lSbu","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}