Subduction of rough seafloor and seamounts is thought to impact a broad range of geodynamic processes, including megathrust slip behaviour, forearc fluid flow and long-term structural evolution in the overriding plate. Although there are many conceptual models describing the effects of seamount subduction, our quantitative and mechanistic understanding of the underlying deformation and fluid processes remains incomplete. Here we investigate the interplay between sediment consolidation, faulting and the evolution of stress and pore fluid pressure in response to seamount subduction, using a numerical model that couples mechanical and hydrological processes and is constrained by laboratory and field observations. Our results show that subducting topography drives marked spatial variations in tectonic loading, sediment consolidation and megathrust stress state. Downdip of a subducting seamount on its leading flank, enhanced compression and drainage lead to large fault-normal stress and overconsolidated wall rocks. A stress shadow in the seamount’s wake leads to anomalously high sediment porosity. These variations help explain observed patterns of megathrust slip, with earthquakes and microseismicity favoured at the downdip edge of seamounts and aseismic or slow slip in the updip stress shadow.
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All the data of earthquake and slow earthquake catalogues and slow slip distributions used in this study have been published by other researchers as referenced in this paper.
The algorithm and the part of code for coupling mechanical and hydrological computation is accessible from the corresponding author upon request.
Wang, K. & Bilek, S. L. Do subducting seamounts generate or stop large earthquakes? Geology 39, 819–822 (2011).
Ding, M. & Lin, J. Deformation and faulting of subduction overriding plate caused by a subducted seamount. Geophys. Res. Lett. 43, 8936–8944 (2016).
Ruh, J. B., Sallarès, V., Ranero, C. R. & Gerya, T. Crustal deformation dynamics and stress evolution during seamount subduction: High‐resolution 3‐D numerical modeling. J. Geophys. Res. Solid Earth 121, 6880–6902 (2016).
von Huene, R. & Scholl, D. W. Observations at convergent margins concerning sediment subduction, subduction erosion, and the growth of continental crust. Rev. Geophys. 29, 279–316 (1991).
Kopp, H. Invited review paper: The control of subduction zone structural complexity and geometry on margin segmentation and seismicity. Tectonophysics 589, 1–16 (2013).
Bassett, D. & Watts, A. B. Gravity anomalies, crustal structure, and seismicity at subduction zones: 2. Interrelationships between fore‐arc structure and seismogenic behavior. Geochem. Geophys. Geosyst. 16, 1541–1576 (2015).
Sahling, H. et al. Fluid seepage at the continental margin offshore Costa Rica and southern Nicaragua. Geochem. Geophys. Geosyst. 9, Q05S05 (2008).
Cloos, M. Thrust-type subduction-zone earthquakes and seamount asperities: A physical model for seismic rupture. Geology 20, 601–604 (1992).
Scholz, C. H. & Small, C. The effect of seamount subduction on seismic coupling. Geology 25, 487–490 (1997).
Mochizuki, K., Yamada, T., Shinohara, M., Yamanaka, Y. & Kanazawa, T. Weak interplate coupling by seamounts and repeating M ~7 earthquakes. Science 321, 1194–1197 (2008).
Wang, K. & Bilek, S. L. Invited review paper: Fault creep caused by subduction of rough seafloor relief. Tectonophysics 610, 1–24 (2014).
Nakatani, Y. et al. Changes in seismicity before and after the 2011 Tohoku earthquake around its southern limit revealed by dense ocean bottom seismic array data. Geophys. Res. Lett. 42, 1384–1389 (2015).
Das, S. & Watts, A. B. in Subduction Zone Geodynamics (eds Lallemand, S. & Funicello, F.) 103–118 (Springer, 2009).
Van Rijsingen, E. et al. How subduction interface roughness influences the occurrence of large interplate earthquakes. Geochem. Geophys. Geosyst. 19, 2342–2370 (2018).
Saffer, D. M. & Wallace, L. M. The frictional, hydrologic, metamorphic and thermal habitat of shallow slow earthquakes. Nat. Geosci. 8, 594 (2015).
Bürgmann, R. The geophysics, geology and mechanics of slow fault slip. Earth Planet. Sci. Lett. 495, 112–134 (2018).
Wallace, L. M. et al. Slow slip near the trench at the Hikurangi subduction zone, New Zealand. Science 352, 701–704 (2016).
Todd, E. K. et al. Earthquakes and tremor linked to seamount subduction during shallow slow slip at the Hikurangi Margin, New Zealand. J. Geophys. Res. Solid Earth 123, 6769–6783 (2018).
Yamashita, Y. et al. Migrating tremor off southern Kyushu as evidence for slow slip of a shallow subduction interface. Science 348, 676–679 (2015).
Nishikawa, T. et al. The slow earthquake spectrum in the Japan Trench illuminated by the S-net seafloor observatories. Science 365, 808–813 (2019).
Vallée, M. et al. Intense interface seismicity triggered by a shallow slow slip event in the Central Ecuador subduction zone. J. Geophys. Res. Solid Earth 118, 2965–2981 (2013).
Rolandone, F. et al. Areas prone to slow slip events impede earthquake rupture propagation and promote afterslip. Sci. Adv. 4, eaao6596 (2018).
Nakano, M., Hori, T., Araki, E., Kodaira, S. & Ide, S. Shallow very-low-frequency earthquakes accompany slow slip events in the Nankai subduction zone. Nat. Commun. 9, 984 (2018).
Shaddox, H. R. & Schwartz, S. Y. Subducted seamount diverts shallow slow slip to the forearc of the northern Hikurangi subduction zone, New Zealand. Geology 47, 415–418 (2019).
Morgan, J. K. & Bangs, N. L. Recognizing seamount-forearc collisions at accretionary margins: Insights from discrete numerical simulations. Geology 45, 635–638 (2017).
Dominguez, S., Malavieille, J. & Lallemand, S. E. Deformation of accretionary wedges in response to seamount subduction: Insights from sandbox experiments. Tectonics 19, 182–196 (2000).
Van Rijsingen, E., Funiciello, F., Corbi, F. & Lallemand, S. Rough subducting seafloor reduces interseismic coupling and mega‐earthquake occurrence: insights from analogue models. Geophys. Res. Lett. 46, 3124–3132 (2019).
Saffer, D. M. & Tobin, H. J. Hydrogeology and mechanics of subduction zone forearcs: Fluid flow and pore pressure. Annu. Rev. Earth Planet. Sci. 39, 157–186 (2011).
Lauer, R. M. & Saffer, D. M. The impact of splay faults on fluid flow, solute transport, and pore pressure distribution in subduction zones: A case study offshore the Nicoya Peninsula, Costa Rica. Geochem. Geophys. Geosyst. 16, 1089–1104 (2015).
Wells, R. E., Blakely, R. J., Wech, A. G., McCrory, P. A. & Michael, A. Cascadia subduction tremor muted by crustal faults. Geology 45, 515–518 (2017).
Moore, J. C. & Saffer, D. Updip limit of the seismogenic zone beneath the accretionary prism of southwest Japan: An effect of diagenetic to low-grade metamorphic processes and increasing effective stress. Geology 29, 183–186 (2001).
Scholz, C. H. Earthquakes and friction laws. Nature 391, 37 (1998).
Han, S., Bangs, N. L., Carbotte, S. M., Saffer, D. M. & Gibson, J. C. Links between sediment consolidation and Cascadia megathrust slip behaviour. Nat. Geosci. 10, 954 (2017).
Ellis, S. et al. Fluid budgets along the northern Hikurangi subduction margin, New Zealand: the effect of a subducting seamount on fluid pressure. Geophys. J. Int. 202, 277–297 (2015).
Barker, D. H. et al. Geophysical constraints on the relationship between seamount subduction, slow slip, and tremor at the North Hikurangi subduction zone, New Zealand. Geophys. Res. Lett. 45, 12–804 (2018).
Flemings, P. B. & Saffer, D. M. Pressure and stress prediction in the Nankai accretionary prism: a critical state soil mechanics porosity‐based approach. J. Geophys. Res. Solid Earth 123, 1089–1115 (2018).
Ranero, C. R. et al. Hydrogeological system of erosional convergent margins and its influence on tectonics and interplate seismogenesis. Geochem. Geophys. Geosyst. 9, Q03S04 (2008).
Caine, J. S., Evans, J. P. & Forster, C. B. Fault zone architecture and permeability structure. Geology 24, 1025 (1996).
Mitchell, T. M. & Faulkner, D. R. Towards quantifying the matrix permeability of fault damage zones in low porosity rocks. Earth Planet. Sci. Lett. 339-340, 24–31 (2012).
Tobin, H. J. & Saffer, D. M. Elevated fluid pressure and extreme mechanical weakness of a plate boundary thrust, Nankai Trough subduction zone. Geology 37, 679–682 (2009).
Moore, J. C. et al. Abnormal fluid pressures and fault-zone dilation in the Barbados accretionary prism: Evidence from logging while drilling. Geology 23, 605–608 (1995).
Gibson, R. E. The progress of consolidation in a clay layer increasing in thickness with time. Geotechnique 8, 171–182 (1958).
Hoffman, N. W. & Tobin, H. J. in Proceedings of the Ocean Drilling Program Scientific Results Vol. 190/196 (eds. Mikada, H. et al.) Ch. 11 (Ocean Drilling Program, 2004).
Kodaira, S., Takahashi, N., Nakanishi, A., Miura, S. & Kaneda, Y. Subducted seamount imaged in the rupture zone of the 1946 Nankaido earthquake. Science 289, 104–106 (2000).
Collot, J. Y. et al. Subducted oceanic relief locks the shallow megathrust in central Ecuador. J. Geophys. Res. Solid Earth 122, 3286–3305 (2017).
Marone, C., & Saffer, D. M. in The Seismogenic Zone of Subduction Thrust Faults (eds Dixon, T. H. & Casey, J. M) Ch. 12 (Columbia University Press, 2007).
Marone, C. Laboratory-derived friction laws and their application to seismic faulting. Annu. Rev. Earth Planet. Sci. 26, 643–696 (1998).
Leeman, J. R., Saffer, D. M., Scuderi, M. M. & Marone, C. Laboratory observations of slow earthquakes and the spectrum of tectonic fault slip modes. Nat. Commun. 7, 11104 (2016).
Liu, Y. & Rice, J. R. Spontaneous and triggered aseismic deformation transients in a subduction fault model. J. Geophys. Res. Solid Earth 112, B09404 (2007).
Davis, E. et al. Episodic deformation and inferred slow slip at the Nankai subduction zone during the first decade of CORK borehole pressure and VLFE monitoring. Earth Planet. Sci. Lett. 368, 110–118 (2013).
Ellis, S. M., Little, T. A., Wallace, L. M., Hacker, B. R. & Buiter, S. J. H. Feedback between rifting and diapirism can exhume ultrahigh-pressure rocks. Earth Planet. Sci. Lett. 311, 427–438 (2011).
Buiter, S. & Ellis, S. SULEC: Benchmarking a new ALE finite-element code. In EGU General Assembly Conference Abstracts Vol. 14 abstr. 7528 (2012).
Wojciechowski, M. A note on the differences between Drucker-Prager and Mohr-Coulomb shear strength criteria. Stud. Geotech. Mech. 40, 163–169 (2018).
Dahlen, F. A. Noncohesive critical Coulomb wedges: An exact solution. J. Geophys. Res. Solid Earth 89, 10125–10133 (1984).
Terzaghi, K., Peck, R. B. & Mesri, G. Soil Mechanics (John Wiley & Sons, 1996).
Kitajima, H. & Saffer, D. M. Consolidation state of incoming sediments to the Nankai Trough subduction zone: Implications for sediment deformation and properties. Geochem. Geophys. Geosyst. 15, 2821–2839 (2014).
Saffer, D. M. Pore pressure development and progressive dewatering in underthrust sediments at the Costa Rican subduction margin: Comparison with northern Barbados and Nankai. J. Geophys. Res. Solid Earth 108, 2261 (2003).
Long, H., Flemings, P. B., Germaine, J. T. & Saffer, D. M. Consolidation and overpressure near the seafloor in the Ursa Basin, Deepwater Gulf of Mexico. Earth Planet. Sci. Lett. 305, 11–20 (2011).
Bray, C. J. & Karig, D. E. Porosity of sediments in accretionary prisms and some implications for dewatering processes. J. Geophys. Res. Solid Earth 90, 768–778 (1985).
Wang, H. F. Theory of Linear Poroelasticity with Applications to Geomechanics and Hydrogeology (Princeton Univ. Press, 2000).
Gamage, K., Screaton, E., Bekins, B. & Aiello, I. Permeability-porosity relationships of subduction zone sediments. Mar. Geol. 279, 19–36 (2011).
Neuzil, C. E. How permeable are clays and shales? Water Resour. Res. 30, 145–150 (1994).
Saffer, D. M. & Bekins, B. A. Episodic fluid flow in the Nankai accretionary complex: Timescale, geochemistry, flow rates, and fluid budget. J. Geophys. Res. Solid Earth 103, 30351–30370 (1998).
Spinelli, G. A. & Wang, K. Effects of fluid circulation in subducting crust on Nankai margin seismogenic zone temperatures. Geology 36, 887–890 (2008).
Hüpers, A. & Kopf, A. J. Effect of smectite dehydration on pore water geochemistry in the shallow subduction zone: An experimental approach. Geochem. Geophys. Geosyst. 13, Q0AD26 (2012).
Kitajima, H. & Saffer, D. M. Elevated pore pressure and anomalously low stress in regions of low frequency earthquakes along the Nankai Trough subduction megathrust. Geophys. Res. Lett. 39, L23301 (2012).
Tsuji, T. et al. Modern and ancient seismogenic out-of-sequence thrusts in the Nankai accretionary prism: Comparison of laboratory-derived physical properties and seismic reflection data. Geophys. Res. Lett. 33, L18309 (2006).
Kikuchi, M., Yamanaka, Y., Abe, K. & Morita, Y. Source rupture process of the Papua New Guinea earthquake of July 17, 1998 inferred from teleseismic body waves. Earth Planets Space 51, 1319–1324 (1999).
Hirata, N. & Matsu’ura, M. Maximum-likelihood estimation of hypocenter with origin time eliminated using nonlinear inversion technique. Phys. Earth Planet. In. 47, 50–61 (1987).
Kubo, H., Asano, K. & Iwata, T. Source‐rupture process of the 2011 Ibaraki‐Oki, Japan, earthquake (Mw 7.9) estimated from the joint inversion of strong‐motion and GPS Data: Relationship with seamount and Philippine Sea Plate. Geophys. Res. Lett. 40, 3003–3007 (2013).
Uchida, N. & Matsuzawa, T. Pre-and postseismic slow slip surrounding the 2011 Tohoku-Oki earthquake rupture. Earth Planet. Sci. Lett. 374, 81–91 (2013).
Neidell, N. S. & Taner, M. T. Semblance and other coherency measures for multichannel data. Geophysics 36, 482–497 (1971).
Matsuzawa, T., Asano, Y. & Obara, K. Very low frequency earthquakes off the Pacific coast of Tohoku, Japan. Geophys. Res. Lett. 42, 4318–4325 (2015).
Okada, Y. et al. Recent progress of seismic observation networks in Japan—Hi-net, F-net, K-NET and KiK-net. Earth Planets Space 56, xv–xxviii (2004).
Nishikawa, T. & Ide, S. Recurring slow slip events and earthquake nucleation in the source region of the M 7 Ibaraki‐Oki earthquakes revealed by earthquake swarm and foreshock activity. J. Geophys. Res. Solid Earth 123, 7950–7968 (2018).
Ueno, H. et al. Improvement of hypocenter determination procedures in the Japan Meteorological Agency. Q. J. Seismology 65, 123–134 (2002).
Okada, Y. Surface deformation due to shear and tensile faults in a half-space. B. Seismol. Soc. Am. 75, 1135–1154 (1985).
Ohta, K. et al. Tremor and inferred slow slip associated with afterslip of the 2011 Tohoku earthquake. Geophys. Res. Lett. 46, 4591–4598 (2019).
Sun, T., Wang, K. & He, J. Crustal deformation following great subduction earthquakes controlled by earthquake size and mantle rheology. J. Geophys. Res. Solid Earth 123, 5323–5345 (2018).
Tomita, F., Kido, M., Ohta, Y., Iinuma, T. & Hino, R. Along-trench variation in seafloor displacements after the 2011 Tohoku earthquake. Sci. Adv. 3, e1700113 (2017).
Baba, T. & Cummins, P. R. Contiguous rupture areas of two Nankai Trough earthquakes revealed by high-resolution tsunami waveform inversion. Geophys. Res. Lett. 32, L08305 (2005).
Mogi, K. Development of aftershock areas of great earthquakes. B. Earthq. Res. Tokyo 46, 175 (1968).
Takemura, S. et al. Structural characteristics of the Nankai Trough shallow plate boundary inferred from shallow very low frequency earthquakes. Geophys. Res. Lett. 46, 4192–4201 (2019).
Takemura, S., Matsuzawa, T., Kimura, T., Tonegawa, T. & Shiomi, K. Centroid moment tensor inversion of shallow very low frequency earthquakes off the Kii Peninsula, Japan, Using a three‐dimensional velocity structure model. Geophys. Res. Lett. 45, 6450–6458 (2018).
Font, Y., Segovia, M., Vaca, S. & Theunissen, T. Seismicity patterns along the Ecuadorian subduction zone: new constraints from earthquake location in a 3-D a priori velocity model. Geophys. J. Int. 193, 263–286 (2013).
Segovia, M. et al. Seismicity distribution near a subducting seamount in the central Ecuadorian subduction zone, space‐time relation to a slow‐slip event. Tectonics 37, 2106–2123 (2018).
Todd, E. K. & Schwartz, S. Y. Tectonic tremor along the northern Hikurangi Margin, New Zealand, between 2010 and 2015. J. Geophys. Res. Solid Earth 121, 8706–8719 (2016).
Eberhart-Phillips, D., Reyners, M., Bannister, S., Chadwick, M. & Ellis, S. Establishing a versatile 3-D seismic velocity model for New Zealand. Seismol. Res. Lett. 81, 992–1000 (2010).
Yarce, J. et al. Seismicity at the Northern Hikurangi Margin, New Zealand, and Investigation of the potential spatial and temporal relationships with a shallow slow slip event. J. Geophys. Res. Solid Earth 124, 4751–4766 (2019).
Bell, R., Holden, C., Power, W., Wang, X. & Downes, G. Hikurangi margin tsunami earthquake generated by slow seismic rupture over a subducted seamount. Earth Planet. Sci. Lett. 397, 1–9 (2014).
Bassin, C., Laske, G. & Masters, G. The current limits of resolution for surface wave tomography in North America. Eos 81, F897 (2000).
Williams, C. A. et al. Revised interface geometry for the Hikurangi subduction zone, New Zealand. Seismol. Res. Lett. 84, 1066–1073 (2013).
Warren-Smith, E. et al. Episodic stress and fluid pressure cycling in subducting oceanic crust during slow slip. Nat. Geosci. 12, 475–481 (2019).
Constructive comments from Jonas Ruh and an anonymous reviewer are greatly appreciated. This study was funded by NSF EAR Award no. 1616664 to D.S., and an IODP Exp 380 post-cruise award was provided to T.S. by USSSP. S.E. was supported by core funding to GNS Science and by a MBIE Endeavour fund. The mechanical code SULEC was modified from an existing version jointly written by S.E. and Susanne Buiter. We thank Kelin Wang, Earl Davis and members of the SHIRE project for helpful discussions.
The authors declare no competing interests.
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Extended Data Fig. 1 Consolidation curves and corresponding compaction loading efficiency of the sediment matrix (black) and the oceanic slab (blue).
a, Small black dots represent laboratory and shipboard experimental results using sediment samples from Nankai off-Kumano56. Larger grey dots show field-based (borehole logging) measurements from Nankai off-Muroto and Barbados57. The four numerical digits, sometimes with a “C” in the front, indicate site numbers of the International Ocean Drilling Program. Measurements made on the sedimentary rock samples of Nias Sumatra outcrop are from ref. 59. b, Compaction loading efficiency is computed using Eqs. (2) and (3) in Methods, assuming a constant fluid compressibility of 5 × 10−10 Pa−1 and incompressible solid grain.
a, Log-linear relationship between matrix permeability and porosity is assigned for the sediment matrix (black thick line) and the oceanic slab (blue thick line). For sediment matrix, this porosity dependence is supported by the results of laboratory experiments on various types of sediments, including argillaceous sediments62 (grey box) and mudstones and sandstones56,65 (other symbols). b, To account for the hydraulic effects of permeable fault damage zones, permeability is enhanced by a factor that linearly scales with the shear strain (see Methods).
Three models with different functions of enhancement factor but otherwise identical input parameters show similar model-predicted patterns of fluid overpressure, fault structure, and sediment consolidation. Grey dashed lines indicate the plate interface. See Fig. 2 caption for definition of parameters. See Extended Data Table 1 for input model parameters.
Extended Data Fig. 5 Empirical relationship between seismic P wave velocity (VP) and sediment porosity (ref. 43).
This is originally based on field measurements for sediments at the Nankai Trough subduction zone (offshore of Cape Muroto). This function is used to obtain the synthetic VP profile shown in Fig. 3a. Data shown here for comparison include shipboard measurements for sediments at Nankai (offshore of the Kii Peninsula56), results of laboratory consolidation tests and measurements66 (dots in colors), and measurements for Shimanto Belt shales from Nankai67.
A subducting sediment layer is assigned between the décollement and the subducting seamount. Grey dashed lines indicate the plate interface. See Fig. 2 caption for definition of parameters. See Extended Data Table 1 for input model parameters. Compared with upper-plate sediment subjected to horizontal compression, modeled porosity values of underthrust sediment are higher owing to the reduction of compressive stress below the plate interface.
Extended Data Fig. 7 Map view of distribution of fault slip behaviour around subducting seamounts at two margins.
a, Central Nankai, and b, Central Ecuador. Grey dashed contours show plate interface depth (in km). In insert, black lines delineate plate boundaries; grey box encloses the zoom-in map area. In a, blue dots show two Ocean Drilling Program boreholes (Holes 808 and 1173) in which fluid pressure records suggest the occurrence of trench-breaching slow slip50. VLFE, very-low-frequency earthquake; SSE, slow slip event. Full summary of the data shown here is in Extended Data Table 3.
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Sun, T., Saffer, D. & Ellis, S. Mechanical and hydrological effects of seamount subduction on megathrust stress and slip. Nat. Geosci. 13, 249–255 (2020). https://doi.org/10.1038/s41561-020-0542-0
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