Abstract
The recognition of slow earthquakes in geodetic and seismological data has transformed the understanding of how plate motions are accommodated at major plate boundaries. Slow earthquakes, which slip more slowly than regular earthquakes but faster than plate motion velocities, occur in a range of tectonic and metamorphic settings. They exhibit spatiotemporal associations with large seismic events that indicate a causal relation between modes of slip at different slip rates. Defining the physical controls on slow earthquakes is, therefore, critical for understanding fault and shear zone mechanics. In this Review, we synthesize geological observations of a suite of ancient structures that were active in tectonic settings comparable to where slow earthquakes are observed today. At inferred slow earthquake regions, a range of grain-scale deformation mechanisms accommodated slip at low effective stresses. Material heterogeneity and the geometric complexity of structures that formed at different inferred strain rates are common to faults and shear zones in multiple tectonic environments, and might represent key limiting factors of slow earthquake slip rates. Further geological work is needed to resolve how the spectrum of slow earthquake slip rates can arise from different grain-scale deformation mechanisms and whether there is one universal rate-limiting mechanism that defines slow earthquake slip.
Key points
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The global distribution and pressure–temperature range of seismologically observed slow earthquake hypocentres implies that no single mineral phase, lithology or metamorphic reaction controls slow earthquake slip.
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There is no universal deformation structure or deformation mechanism that is currently a clear indicator of slow earthquakes in the rock record. Multiple different mechanisms or combinations of mechanisms can produce the same macroscopic behaviours.
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Geological evidence from slow earthquake source regions suggests that material heterogeneity, geometric complexity and deformation at low differential stress are common to slow earthquake sources.
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A seismologically observed low-frequency earthquake source could consist of multiple anastomosing faults, shear bands and/or vein networks (potentially including synchronous slip across multiple subparallel surfaces), rather than a single planar fault surface.
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Geodetically observed slow slip events can be accommodated by ductile shear zones, which are commonly identified in many exhumed fault zones.
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References
Peng, Z. G. & Gomberg, J. An integrated perspective of the continuum between earthquakes and slow-slip phenomena. Nat. Geosci. 3, 599–607 (2010).
Ito, Y. & Obara, K. Very low frequency earthquakes within accretionary prisms are very low stress-drop earthquakes. Geophys. Res. Lett. 33, L09302 (2006).
Obana, K. & Kodaira, S. Low-frequency tremors associated with reverse faults in a shallow accretionary prism. Earth Planet. Sci. Lett. 287, 168–174 (2009).
To, A. et al. Small size very low frequency earthquakes in the Nankai accretionary prism, following the 2011 Tohoku-Oki earthquake. Phys. Earth Planet. Inter. 245, 40–51 (2015).
Kao, H. et al. A wide depth distribution of seismic tremors along the northern Cascadia margin. Nature 436, 841–844 (2005).
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).
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).
Toh, A., Obana, K. & Araki, E. Distribution of very low frequency earthquakes in the Nankai accretionary prism influenced by a subducting-ridge. Earth Planet. Sci. Lett. 482, 342–356 (2018).
Ito, Y. & Obara, K. Dynamic deformation of the accretionary prism excites very low frequency earthquakes. Geophys. Res. Lett. 33, L02311 (2006).
Aiken, C. et al. Exploration of remote triggering: A survey of multiple fault structures in Haiti. Earth Planet. Sci. Lett. 455, 14–24 (2016).
Peng, Z. G. et al. Tectonic tremor beneath Cuba triggered by the Mw 8.8 Maule and Mw 9.0 Tohoku-Oki earthquakes. Bull. Seismol. Soc. Am. 103, 595–600 (2013).
Chao, K. & Obara, K. Triggered tectonic tremor in various types of fault systems of Japan following the 2012 Mw8.6 Sumatra earthquake. J. Geophys. Res. Solid Earth 121, 170–187 (2016).
Gomberg, J. et al. Widespread triggering of nonvolcanic tremor in California. Science 319, 173–173 (2008).
Chao, K. et al. A global search for triggered tremor following the 2011 Mw 9.0 Tohoku earthquake. Bull. Seismol. Soc. Am. 103, 1551–1571 (2013).
Wang, T. H., Cochran, E. S., Agnew, D. & Oglesby, D. D. Infrequent triggering of tremor along the San Jacinto fault near Anza, California. Bull. Seismol. Soc. Am. 103, 2482–2497 (2013).
Scarpa, R. et al. Slow earthquakes and low frequency tremor along the Apennines, Italy. Ann. Geophys. 51, 527–538 (2008).
Jolivet, R. & Frank, W. B. The transient and intermittent nature of slow slip. AGU Adv. 1, e2019AV000126 (2020).
Kato, A. et al. Propagation of slow slip leading up to the 2011 Mw 9.0 Tohoku-Oki earthquake. Science 335, 705–708 (2012).
Wallace, L. M. et al. Slow slip near the trench at the Hikurangi subduction zone, New Zealand. Science 352, 701–704 (2016).
Veedu, D. M. & Barbot, S. The Parkfield tremors reveal slow and fast ruptures on the same asperity. Nature 532, 361–365 (2016).
Wech, A. G. & Creager, K. C. A continuum of stress, strength and slip in the Cascadia subduction zone. Nat. Geosci. 4, 624–628 (2011).
Araki, E. et al. Recurring and triggered slow-slip events near the trench at the Nankai Trough subduction megathrust. Science 356, 1157–1160 (2017).
Obara, K. & Kato, A. Connecting slow earthquakes to huge earthquakes. Science 353, 253–257 (2016).
Kano, M., Kato, A. & Obara, K. Episodic tremor and slip silently invades strongly locked megathrust in the Nankai Trough. Sci. Rep. 9, 9270 (2019).
Obara, K. Nonvolcanic deep tremor associated with subduction in southwest Japan. Science 296, 1679–1681 (2002).
Shelly, D. R., Beroza, G. C. & Ide, S. Non-volcanic tremor and low-frequency earthquake swarms. Nature 446, 305–307 (2007).
Rogers, G. & Dragert, H. Episodic tremor and slip on the Cascadia subduction zone: The chatter of silent slip. Science 300, 1942–1943 (2003).
Ito, Y., Obara, K., Shiomi, K., Sekine, S. & Hirose, H. Slow earthquakes coincident with episodic tremors and slow slip events. Science 315, 503–506 (2007).
Gomberg, J., Wech, A., Creager, K., Obara, K. & Agnew, D. Reconsidering earthquake scaling. Geophys. Res. Lett. 43, 6243–6251 (2016).
Frank, W. B. & Brodsky, E. E. Daily measurement of slow slip from low-frequency earthquakes is consistent with ordinary earthquake scaling. Sci. Adv. 5, eaaw9386 (2019).
Behr, W. M. & Burgman, R. What’s down there? The structures, materials and environment of deep-seated slow slip and tremor. Philos. Trans. R. Soc. A 379, 20200218 (2020).
Ikari, M. J. Laboratory slow slip events in natural geological materials. Geophys. J. Int. 218, 354–387 (2019).
Ikari, M. J., Ito, Y., Ujiie, K. & Kopf, A. J. Spectrum of slip behaviour in Tohoku fault zone samples at plate tectonic slip rates. Nat. Geosci. 8, 870–874 (2015).
Leeman, J. R., Marone, C. & Saffer, D. M. Frictional mechanics of slow earthquakes. J. Geophys. Res. Solid Earth 123, 7931–7949 (2018).
Reber, J. E., Lavier, L. L. & Hayman, N. W. Experimental demonstration of a semi-brittle origin for crustal strain transients. Nat. Geosci. 8, 712–715 (2015).
Fagereng, A., Remitti, F. & Sibson, R. H. Incrementally developed slickenfibers—Geological record of repeating low stress-drop seismic events? Tectonophysics 510, 381–386 (2011).
Ujiie, K. et al. An explanation of episodic tremor and slow slip constrained by crack-seal veins and viscous shear in subduction melange. Geophys. Res. Lett. 45, 5371–5379 (2018).
Behr, W. M., Kotowski, A. J. & Ashley, K. T. Dehydration-induced rheological heterogeneity and the deep tremor source in warm subduction zones. Geology 46, 475–478 (2018).
Kotowski, A. J. & Behr, W. M. Length scales and types of heterogeneities along the deep subduction interface: Insights from exhumed rocks on Syros Island, Greece. Geosphere 15, 1038–1065 (2019).
Tarling, M. S., Smith, S. A. F. & Scott, J. M. Fluid overpressure from chemical reactions in serpentinite within the source region of deep episodic tremor. Nat. Geosci. 12, 1034–1042 (2019).
Platt, J. P., Xia, H. R. & Schmidt, W. L. Rheology and stress in subduction zones around the aseismic/seismic transition. Prog. Earth Planet. Sci. 5, 24 (2018).
Hayman, N. W. & Lavier, L. L. The geologic record of deep episodic tremor and slip. Geology 42, 195–198 (2014).
Angiboust, S. et al. Probing the transition between seismically coupled and decoupled segments along an ancient subduction interface. Geochem. Geophys. Geosystems 16, 1905–1922 (2015).
Saito, T., Ujiie, K., Tsutsumi, A., Kameda, J. & Shibazaki, B. Geological and frictional aspects of very-low-frequency earthquakes in an accretionary prism. Geophys. Res. Lett. 40, 703–708 (2013).
Saffer, D. M. & Wallace, L. M. The frictional, hydrologic, metamorphic and thermal habitat of shallow slow earthquakes. Nat. Geosci. 8, 594–600 (2015).
Audet, P. & Kim, Y. Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review. Tectonophysics 670, 1–15 (2016).
Rubinstein, J. L., Shelly, D. R. & Ellsworth, W. L. in New Frontiers in Integrated Solid Earth Sciences (eds Cloetingh, S. & Negendank, J.) 287–314 (Springer, 2010).
Royer, A. A. & Bostock, M. G. A comparative study of low frequency earthquake templates in northern Cascadia. Earth Planet. Sci. Lett. 402, 247–256 (2014).
Chestler, S. R. & Creager, K. C. A model for low-frequency earthquake slip. Geochem. Geophys. Geosystems 18, 4690–4708 (2017).
Ide, S., Shelly, D. R. & Beroza, G. C. Mechanism of deep low frequency earthquakes: Further evidence that deep non-volcanic tremor is generated by shear slip on the plate interface. Geophys. Res. Lett. 34, L03308 (2007).
Brown, J. R. et al. Deep low-frequency earthquakes in tremor localize to the plate interface in multiple subduction zones. Geophys. Res. Lett. 36, L19306 (2009).
Harrington, R. M., Cochran, E. S., Griffiths, E. M., Zeng, X. F. & Thurber, C. H. Along-strike variations in fault frictional properties along the San Andreas fault near Cholame, California, from joint earthquake and low-frequency earthquake relocations. Bull. Seismol. Soc. Am. 106, 319–326 (2016).
Walter, J. I., Schwartz, S. Y., Protti, J. M. & Gonzalez, V. Persistent tremor within the northern Costa Rica seismogenic zone. Geophys. Res. Lett. 38, L01307 (2011).
Arai, R. et al. Structure of the tsunamigenic plate boundary and low-frequency earthquakes in the southern Ryukyu Trench. Nat. Commun. 7, 12255 (2016).
Schwartz, S. Y. & Rokosky, J. M. Slow slip events and seismic tremor at circum-Pacific subduction zones. Rev. Geophys. 45, RG3004 (2007).
Wech, A. G., Boese, C. M., Stern, T. A. & Townend, J. Tectonic tremor and deep slow slip on the Alpine Fault. Geophys. Res. Lett. 39, L10303 (2012).
Chamberlain, C. J., Shelly, D. R., Townend, J. & Stern, T. A. Low-frequency earthquakes reveal punctuated slow slip on the deep extent of the Alpine Fault, New Zealand. Geochem. Geophys. Geosystems 15, 2984–2999 (2014).
Hall, K., Houston, H. & Schmidt, D. Spatial comparisons of tremor and slow slip as a constraint on fault strength in the northern Cascadia subduction zone. Geochem. Geophys. Geosystems 19, 2706–2718 (2018).
Shelly, D. R. A 15year catalog of more than 1 million low-frequency earthquakes: Tracking tremor and slip along the deep San Andreas Fault. J. Geophys. Res. Solid Earth 122, 3739–3753 (2017).
Shelly, D. R. Complexity of the deep San Andreas Fault zone defined by cascading tremor. Nat. Geosci. 8, 145–151 (2015).
Obara, K., Tanaka, S., Maeda, T. & Matsuzawa, T. Depth-dependent activity of non-volcanic tremor in southwest Japan. Geophys. Res. Lett. 37, L13306 (2010).
Wech, A. G. Interactive tremor monitoring. Seismol. Res. Lett. 81, 664–669 (2010).
Bostock, M. G., Royer, A. A., Hearn, E. H. & Peacock, S. M. Low frequency earthquakes below southern Vancouver Island. Geochem. Geophys. Geosystems 13, 11 (2012).
Bostock, M. G., Thomas, A. M., Savard, G., Chuang, L. & Rubin, A. M. Magnitudes and moment-duration scaling of low-frequency earthquakes beneath southern Vancouver Island. J. Geophys. Res. Solid Earth 120, 6329–6350 (2015).
Frank, W. B. et al. Low-frequency earthquakes in the Mexican Sweet Spot. Geophys. Res. Lett. 40, 2661–2666 (2013).
Thomas, A. M., Beroza, G. C. & Shelly, D. R. Constraints on the source parameters of low-frequency earthquakes on the San Andreas Fault. Geophys. Res. Lett. 43, 1464–1471 (2016).
Sweet, J. R., Creager, K. C. & Houston, H. A family of repeating low-frequency earthquakes at the downdip edge of tremor and slip. Geochem. Geophys. Geosystems 15, 3713–3721 (2014).
Shelly, D. R. & Hardebeck, J. L. Precise tremor source locations and amplitude variations along the lower-crustal central San Andreas Fault. Geophys. Res. Lett. 37, L14301 (2010).
Allmann, B. P. & Shearer, P. M. Global variations of stress drop for moderate to large earthquakes. J. Geophys. Res. Solid Earth 114, B01310 (2009).
Frank, W. B. Slow slip hidden in the noise: The intermittence of tectonic release. Geophys. Res. Lett. 43, 10125–10133 (2016).
Audet, P. & Schaeffer, A. J. Fluid pressure and shear zone development over the locked to slow slip region in Cascadia. Sci. Adv. 4, eaar2982 (2018).
Song, T. R. A. et al. Subducting slab ultra-slow velocity layer coincident with silent earthquakes in southern Mexico. Science 324, 502–506 (2009).
Shelly, D. R., Beroza, G. C., Ide, S. & Nakamula, S. Low-frequency earthquakes in Shikoku, Japan, and their relationship to episodic tremor and slip. Nature 442, 188–191 (2006).
Kodaira, S. et al. High pore fluid pressure may cause silent slip in the Nankai Trough. Science 304, 1295–1298 (2004).
Audet, P., Bostock, M. G., Christensen, N. I. & Peacock, S. M. Seismic evidence for overpressured subducted oceanic crust and megathrust fault sealing. Nature 457, 76–78 (2009).
Rubinstein, J. L. et al. Non-volcanic tremor driven by large transient shear stresses. Nature 448, 579–582 (2007).
Thomas, A. M., Burgmann, R., Shelly, D. R., Beeler, N. M. & Rudolph, M. L. Tidal triggering of low frequency earthquakes near Parkfield, California: Implications for fault mechanics within the brittle-ductile transition. J. Geophys. Res. Solid Earth 117, B05301 (2012).
Thomas, A. M., Nadeau, R. M. & Burgmann, R. Tremor-tide correlations and near-lithostatic pore pressure on the deep San Andreas fault. Nature 462, 1048–1051 (2009).
van der Elst, N. J., Delorey, A. A., Shelly, D. R. & Johnson, P. A. Fortnightly modulation of San Andreas tremor and low-frequency earthquakes. Proc. Natl Acad. Sci. USA 113, 8601–8605 (2016).
Ghosh, A. et al. Tremor bands sweep Cascadia. Geophys. Res. Lett. 37, L08301 (2010).
Houston, H., Delbridge, B. G., Wech, A. G. & Creager, K. C. Rapid tremor reversals in Cascadia generated by a weakened plate interface. Nat. Geosci. 4, 404–409 (2011).
Moore, J. C., Rowe, C. D. & Meneghini, F. in The Seismogenic Zone of Subduction Thrust Faults Vol. 2 (eds Dixon, T. H. & Moore, J. C.) 288–314 (Columbia Univ. Press, 2007).
Moore, J. C. & Byrne, T. Thickening of fault zones: A mechanism of melange formation in accreting sediments. Geology 15, 1040–1043 (1987).
Rowe, C. D., Moore, J. C., Remitti, F. & Scientist, I. E. T. The thickness of subduction plate boundary faults from the seafloor into the seismogenic zone. Geology 41, 991–994 (2013).
Stenvall, C. A., Fagereng, A. & Diener, J. F. A. Weaker than weakest: on the strength of shear zones. Geophys. Res. Lett. 46, 7404–7413 (2019).
Lister, G. S. & Snoke, A. W. S-C mylonites. J. Struct. Geol. 6, 617–638 (1984).
Goodwin, L. B. & Tikoff, B. Competency contrast, kinematics, and the development of foliations and lineations in the crust. J. Struct. Geol. 24, 1065–1085 (2002).
Ujiie, K., Yamaguchi, H., Sakaguchi, A. & Toh, S. Pseudotachylytes in an ancient accretionary complex and implications for melt lubrication during subduction zone earthquakes. J. Struct. Geol. 29, 599–613 (2007).
Cerchiari, A. et al. Cyclical variations of fluid sources and stress state in a shallow megathrust-zone melange. J. Geol. Soc. 177, 647–659 (2020).
Kimura, G. et al. Hanging wall deformation of a seismogenic megasplay fault in an accretionary prism: The Nobeoka Thrust in southwestern Japan. J. Struct. Geol. 52, 136–147 (2013).
Kimura, G. et al. Tectonic melange as fault rock of subduction plate boundary. Tectonophysics 568, 25–38 (2012).
Rennie, S. F., Fagereng, A. & Diener, J. F. A. Strain distribution within a km-scale, mid-crustal shear zone: the Kuckaus Mylonite Zone, Namibia. J. Struct. Geol. 56, 57–69 (2013).
Fusseis, F., Handy, M. R. & Schrank, C. Networking of shear zones at the brittle-to-viscous transition (Cap de Creus, NE Spain). J. Struct. Geol. 28, 1228–1243 (2006).
Auzende, A. L. et al. Deformation mechanisms of antigorite serpentinite at subduction zone conditions determined from experimentally and naturally deformed rocks. Earth Planet. Sci. Lett. 411, 229–240 (2015).
Boutonnet, E., Leloup, P. H., Sassier, C., Gardien, V. & Ricard, Y. Ductile strain rate measurements document long-term strain localization in the continental crust. Geology 41, 819–822 (2013).
Campbel, L. R. & Menegon, L. Transient high strain rate during localized viscous creep in the dry lower continental crust (Lofoten, Norway). J. Geophys. Res. Solid Earth 124, 10240–10260 (2019).
Berthe, D., Choukroune, P. & Jegouzo, P. Orthogneiss, mylonite and non coaxial deformation of granites: the example of the South Armorican Shear Zone. J. Struct. Geol. 1, 31–42 (1979).
Skarbek, R. M., Rempel, A. W. & Schmidt, D. A. Geologic heterogeneity can produce aseismic slip transients. Geophys. Res. Lett. 39, L21306 (2012).
Fagereng, A. & Sibson, R. H. Melange rheology and seismic style. Geology 38, 751–754 (2010).
Kimura, G. & Mukai, A. Underplated units in an accretionary complex: Melange of the Shimanto Belt of eastern Shikoku, southwest Japan. Tectonics 10, 31–50 (1991).
Fisher, D. & Byrne, T. Structural evolution of underthrusted sediments, Kodiak Islands, Alaska. Tectonics 6, 775–793 (1987).
Remitti, F., Bettelli, G. & Vannucchi, P. Internal structure and tectonic evolution of an underthrust tectonic melange: The Sestola-Vidiciatico tectonic unit of the Northern Apennines, Italy. Geodin. Acta 20, 37–51 (2007).
Vannucchi, P. & Bettelli, G. Mechanisms of subduction accretion as implied from the broken formations in the Apennines, Italy. Geology 30, 835–838 (2002).
Moore, J. C. & Allwardt, A. Progressive deformation of a tertiary trench slope, Kodiak Islands, Alaska. J. Geophys. Res. 85, 4741–4756 (1980).
Festa, A., Ogata, K. & Pini, G. A. Polygenetic mélanges: a glimpse on tectonic, sedimentary and diapiric recycling in convergent margins. J. Geol. Soc. 177, 551–561 (2020).
Schmidt, W. L. & Platt, J. P. Subduction, accretion, and exhumation of coherent Franciscan blueschist-facies rocks, northern Coast Ranges, California. Lithosphere 10, 301–326 (2018).
Laurent, V. et al. Strain localization in a fossilized subduction channel: Insights from the Cycladic Blueschist Unit (Syros, Greece). Tectonophysics 672, 150–169 (2016).
Hermann, J., Muntener, O. & Scambelluri, M. The importance of serpentinite mylonites for subduction and exhumation of oceanic crust. Tectonophysics 327, 225–238 (2000).
Guillot, S., Schwartz, S., Reynard, B., Agard, P. & Prigent, C. Tectonic significance of serpentinites. Tectonophysics 646, 1–19 (2015).
Melosh, B. L., Rowe, C. D., Gerbi, C., Smit, L. & Macey, P. Seismic cycle feedbacks in a mid-crustal shear zone. J. Struct. Geol. 112, 95–111 (2018).
Price, N. A. et al. Recrystallization fabrics of sheared quartz veins with a strong pre-existing crystallographic preferred orientation from a seismogenic shear zone. Tectonophysics 682, 214–236 (2016).
Fagereng, A. Frequency-size distribution of competent lenses in a block-in-matrix mélange: Imposed length scales of brittle deformation? J. Geophys. Res. Solid Earth 116, B05302 (2011).
Kitamura, Y. & Kimura, G. Dynamic role of tectonic melange during interseismic process of plate boundary mega earthquakes. Tectonophysics 568, 39–52 (2012).
Clauset, A., Shalizi, C. R. & Newman, M. E. J. Power-law distributions in empirical data. SIAM Rev. 51, 661–703 (2009).
Kitamura, Y. et al. Mélange and its seismogenic roof décollement: A plate boundary fault rock in the subduction zone—An example from the Shimanto Belt, Japan. Tectonics 24, TC5012 (2005).
Fagereng, A. & den Hartog, S. A. M. Subduction megathrust creep governed by pressure solution and frictional-viscous flow. Nat. Geosci. 10, 51–57 (2017).
Tulley, C. J., Fagereng, A. & Ujiie, K. Hydrous oceanic crust hosts megathrust creep at low shear stresses. Sci. Adv. 6, eaba1529 (2020).
Melosh, B. L. et al. Snap, Crackle, Pop: Dilational fault breccias record seismic slip below the brittle–plastic transition. Earth Planet. Sci. Lett. 403, 432–445 (2014).
Phillips, N. J., Belzer, B., French, M. E., Rowe, C. D. & Ujiie, K. Frictional strengths of subduction thrust rocks in the region of shallow slow earthquakes. J. Geophys. Res. Solid Earth 125, e2019JB018888 (2020).
Swanson, M. T. Fault structure, wear mechanisms and rupture processes in pseudotachylyte generation. Tectonophysics 204, 223–242 (1992).
Price, N. A., Johnson, S. E., Gerbi, C. C. & West, D. P. Identifying deformed pseudotachylyte and its influence on the strength and evolution of a crustal shear zone at the base of the seismogenic zone. Tectonophysics 518, 63–83 (2012).
Goodwin, L. B. & Wenk, H. R. Development of phyllonite from granodiorite: Mechanisms of grain-size reduction in the Santa Rosa mylonite zone, California. J. Struct. Geol. 17, 689–707 (1995).
Niemeijer, A. R. & Spiers, C. J. Influence of phyllosilicates on fault strength in the brittle-ductile transition: Insights from rock analogue experiments. Geol. Soc. Spec. Publ. 245, 303–327 (2005).
Wassmann, S. & Stockhert, B. Rheology of the plate interface—Dissolution precipitation creep in high pressure metamorphic rocks. Tectonophysics 608, 1–29 (2013).
Meneghini, F. & Moore, J. C. Deformation and hydrofracture in a subduction thrust at seismogenic depths: The Rodeo Cove thrust zone, Marin Headlands, California. Geol. Soc. Am. Bull. 119, 174–183 (2007).
Compton, K. E., Kirkpatrick, J. D. & Holk, G. J. Cyclical shear fracture and viscous flow during transitional ductile-brittle deformation in the Saddlebag Lake Shear Zone, California. Tectonophysics 708, 1–14 (2017).
Fagereng, A., Hillary, G. W. B. & Diener, J. F. A. Brittle-viscous deformation, slow slip, and tremor. Geophys. Res. Lett. 41, 4159–4167 (2014).
Palazzin, G. et al. Deformation processes at the down-dip limit of the seismogenic zone: The example of Shimanto accretionary complex. Tectonophysics 687, 28–43 (2016).
Rowe, C. D. et al. Geometric complexity of earthquake rupture surfaces preserved in pseudotachylyte networks. J. Geophys. Res. Solid Earth 123, 7998–8015 (2018).
Melosh, B. L., Rowe, C. D., Gerbi, C., Bate, C. E. & Shulman, D. The spin zone: Transient mid-crust permeability caused by coseismic brecciation. J. Struct. Geol. 87, 47–63 (2016).
Gosselin, J. M. et al. Seismic evidence for megathrust fault-valve behavior during episodic tremor and slip. Sci. Adv. 6, eaay5174 (2020).
Fagereng, A., Remitti, F. & Sibson, R. H. Shear veins observed within anisotropic fabric at high angles to the maximum compressive stress. Nat. Geosci. 3, 482–485 (2010).
French, M. E. & Condit, C. B. Slip partitioning along an idealized subduction plate boundary at deep slow slip conditions. Earth Planet. Sci. Lett. 528, 115828 (2019).
Shea, W. T. & Kronenberg, A. K. Strength and anisotropy of foliated rocks with varied mica contents. J. Struct. Geol. 15, 1097–1121 (1993).
Rowe, C. D., Meneghini, F. & Moore, J. C. Fluid-rich damage zone of an ancient out-of-sequence thrust, Kodiak Islands, Alaska. Tectonics 28, TC1006 (2009).
Fagereng, A., Diener, J. F. A., Meneghini, F., Harris, C. & Kvadsheim, A. Quartz vein formation by local dehydration embrittlement along the deep, tremorgenic subduction thrust interface. Geology 46, 67–70 (2018).
Fabbri, O. et al. Deformation structures from splay and décollement faults in the Nankai accretionary prism, SW Japan (IODP NanTroSEIZE Expedition 316): Evidence for slow and rapid slip in fault rocks. Geochem. Geophys. Geosystems 21, e2019GC008786 (2020).
Bos, B. & Spiers, C. J. Frictional-viscous flow of phyllosilicate-bearing fault rock: Microphysical model and implications for crustal strength profiles. J. Geophys. Res. Solid Earth 107, 2028 (2002).
Rowe, C. D., Meneghini, F. & Moore, J. C. in Geology of the Earthquake Source: a Volume in Honour of Rick Sibson Vol. 359 (eds Fagereng, A. Toy, V. G. & Rowland, J. V.) 77–95 (Geological Society Special Publication, 2011).
Rutter, E. H., Maddock, R. H., Hall, S. H. & White, S. H. Comparative microstructures of natural and experimentally produced clay-bearing fault gouges. Pure Appl. Geophys. 124, 3–30 (1986).
Kirkpatrick, J. D. et al. Structure and lithology of the Japan Trench subduction plate boundary fault. Tectonics 34, 53–69 (2015).
Fagereng, A. et al. Mixed deformation styles observed on a shallow subduction thrust, Hikurangi margin, New Zealand. Geology 47, 872–876 (2019).
Beall, A., Fagereng, A. & Ellis, S. Strength of strained two-phase mixtures: application to rapid creep and stress amplification in subduction zone melange. Geophys. Res. Lett. 46, 169–178 (2019).
Sibson, R. H. Tensile overpressure compartments on low-angle thrust faults. Earth Planets Space 69, 113 (2017).
Sibson, R. H. Structural permeability of fluid-driven fault-fracture meshes. J. Struct. Geol. 18, 1031–1042 (1996).
Beall, A., Fagereng, A. & Ellis, S. Fracture and weakening of jammed subduction shear zones, leading to the generation of slow slip events. Geochem. Geophys. Geosystems 20, 4869–4884 (2019).
Stunitz, H. & Tullis, J. Weakening and strain localization produced by syn-deformational reaction of plagioclase. Int. J. Earth Sci. 90, 136–148 (2001).
Chestler, S. R. & Creager, K. C. Evidence for a scale-limited low-frequency earthquake source process. J. Geophys. Res. Solid Earth 122, 3099–3114 (2017).
Nakano, M., Yabe, S., Sugioka, H., Shinohara, M. & Ide, S. Event size distribution of shallow tectonic tremor in the Nankai trough. Geophys. Res. Lett. 46, 5828–5836 (2019).
Rubin, A. M. Designer friction laws for bimodal slow slip propagation speeds. Geochem. Geophys. Geosystems 12, 4 (2011).
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. J. & Rice, J. R. Spontaneous and triggered aseismic deformation transients in a subduction fault model. J. Geophys. Res. Solid Earth 112, B09404 (2007).
Hawthorne, J. C. & Rubin, A. M. Laterally propagating slow slip events in a rate and state friction model with a velocity-weakening to velocity-strengthening transition. J. Geophys. Res. Solid Earth 118, 3785–3808 (2013).
Shibazaki, B. & Shimamoto, T. Modelling of short-interval silent slip events in deeper subduction interfaces considering the frictional properties at the unstable–stable transition regime. Geophys. J. Int. 171, 191–205 (2007).
Im, K., Saffer, D., Marone, C. & Avouac, J. P. Slip-rate-dependent friction as a universal mechanism for slow slip events. Nat. Geosci. 13, 705–710 (2020).
Segall, P., Rubin, A. M., Bradley, A. M. & Rice, J. R. Dilatant strengthening as a mechanism for slow slip events. J. Geophys. Res. Solid Earth 115, B12305 (2010).
Liu, Y. J. & Rubin, A. M. Role of fault gouge dilatancy on aseismic deformation transients. J. Geophys. Res. Solid Earth 115, B10414 (2010).
Romanet, P., Bhat, H. S., Jolivet, R. & Madariaga, R. Fast and slow slip events emerge due to fault geometrical complexity. Geophys. Res. Lett. 45, 4809–4819 (2018).
Ikari, M. J. & Saffer, D. M. Comparison of frictional strength and velocity dependence between fault zones in the Nankai accretionary complex. Geochem. Geophys. Geosystems 12, 4 (2011).
Roesner, A. et al. Friction experiments under in-situ stress reveal unexpected velocity-weakening in Nankai accretionary prism samples. Earth Planet. Sci. Lett. 538, 116180 (2020).
Kaproth, B. M. & Marone, C. Slow earthquakes, preseismic velocity changes, and the origin of slow frictional stick-slip. Science 341, 1229–1232 (2013).
Phillips, N. J., Motohashi, G., Ujiie, K. & Rowe, C. D. Evidence of localized failure along altered basaltic blocks in tectonic mélange at the updip limit of the seismogenic zone: implications for the shallow slow earthquake source. Geochem. Geophys. Geosystems 21, e2019GC008839 (2020).
Gratier, J. P., Favreau, P., Renard, F. & Pili, E. Fluid pressure evolution during the earthquake cycle controlled by fluid flow and pressure solution crack sealing. Earth Planets Space 54, 1139–1146 (2002).
van den Ende, M. P. A. & Niemeijer, A. R. Time-dependent compaction as a mechanism for regular stick-slips. Geophys. Res. Lett. 45, 5959–5967 (2018).
Hobbs, B. E., Ord, A. & Teyssier, C. Earthquakes in the ductile regime. Pure Appl. Geophys. 124, 309–336 (1986).
Sibson, R. H. Transient discontinuities in ductile shear zones. J. Struct. Geol. 2, 165–171 (1980).
French, M. E., Hirth, G. & Okazaki, K. Fracture-induced pore fluid pressure weakening and dehydration of serpentinite. Tectonophysics 767, 228168 (2019).
Kato, A., Sakaguchi, A., Yoshida, S., Yamaguchi, H. & Kaneda, Y. Permeability structure around an ancient exhumed subduction-zone fault. Geophys. Res. Lett. 31, L06602 (2004).
Kawano, S., Katayama, I. & Okazaki, K. Permeability anisotropy of serpentinite and fluid pathways in a subduction zone. Geology 39, 939–942 (2011).
Okazaki, K., Katayama, I. & Noda, H. Shear-induced permeability anisotropy of simulated serpentinite gouge produced by triaxial deformation experiments. Geophys. Res. Lett. 40, 1290–1294 (2013).
Daigle, H. & Screaton, E. J. Evolution of sediment permeability during burial and subduction. Geofluids 15, 84–105 (2015).
Okazaki, K. & Katayama, I. Slow stick slip of antigorite serpentinite under hydrothermal conditions as a possible mechanism for slow earthquakes. Geophys. Res. Lett. 42, 1099–1104 (2015).
White, J. C. Paradoxical pseudotachylyte–Fault melt outside the seismogenic zone. J. Struct. Geol. 38, 11–20 (2012).
Gilgannon, J. et al. Experimental evidence that viscous shear zones generate periodic pore sheets that focus mass transport. Solid Earth https://doi.org/10.5194/se-2020-137 (2020).
Rubin, A. M. Episodic slow slip events and rate-and-state friction. J. Geophys. Res. Solid Earth 113, B11414 (2008).
Daub, E. G., Shelly, D. R., Guyer, R. A. & Johnson, P. A. Brittle and ductile friction and the physics of tectonic tremor. Geophys. Res. Lett. 38, L10301 (2011).
Hawthorne, J. C., Thomas, A. M. & Ampuero, J. P. The rupture extent of low frequency earthquakes near Parkfield, CA. Geophys. J. Int. 216, 621–639 (2019).
Bostock, M. G., Thomas, A. M., Rubin, A. M. & Christensen, N. I. On corner frequencies, attenuation, and low-frequency earthquakes. J. Geophys. Res. Solid Earth 122, 543–557 (2017).
Nowack, R. L. & Bostock, M. G. Scattered waves from low-frequency earthquakes and plate boundary structure in northern Cascadia. Geophys. Res. Lett. 40, 4238–4243 (2013).
Ghosh, A. et al. Rapid, continuous streaking of tremor in Cascadia. Geochem. Geophys. Geosystems 11, 12 (2010).
Audet, P. & Burgmann, R. Possible control of subduction zone slow-earthquake periodicity by silica enrichment. Nature 510, 389–392 (2014).
Houston, H. Low friction and fault weakening revealed by rising sensitivity of tremor to tidal stress. Nat. Geosci. 8, 409–415 (2015).
Sweet, J. R., Creager, K. C., Houston, H. & Chestler, S. R. Variations in Cascadia low-frequency earthquake behavior with downdip distance. Geochem. Geophys. Geosystems 20, 1202–1217 (2019).
Hall, K., Schmidt, D. & Houston, H. Peak tremor rates lead peak slip rates during propagation of two large slow earthquakes in Cascadia. Geochem. Geophys. Geosystems 20, 4665–4675 (2019).
Obara, K., Hirose, H., Yamamizu, F. & Kasahara, K. Episodic slow slip events accompanied by non-volcanic tremors in southwest Japan subduction zone. Geophys. Res. Lett. 31, L23602 (2004).
Shelly, D. R., Beroza, G. C. & Ide, S. Complex evolution of transient slip derived from precise tremor locations in western Shikoku, Japan. Geochem. Geophys. Geosystems 8, 10 (2007).
Rubinstein, J. L., La Rocca, M., Vidale, J. E., Creager, K. C. & Wech, A. G. Tidal modulation of nonvolcanic tremor. Science 319, 186–189 (2008).
Bostock, M. G. & Christensen, N. I. Split from slip and schist: Crustal anisotropy beneath northern Cascadia from non-volcanic tremor. J. Geophys. Res. Solid Earth 117, B08303 (2012).
Zal, H. J. et al. Temporal and spatial variations in seismic anisotropy and VP/VS ratios in a region of slow slip. Earth Planet. Sci. Lett. 532, 115970 (2020).
Peacock, S. M. Thermal and metamorphic environment of subduction zone episodic tremor and slip. J. Geophys. Res. Solid Earth 114, B00A07 (2009).
Ujiie, K., Yamaguchi, A., Kimura, G. & Toh, S. Fluidization of granular material in a subduction thrust at seismogenic depths. Earth Planet. Sci. Lett. 259, 307–318 (2007).
Acknowledgements
We thank Yujin Kitamura and Alissa Kotowski for providing data for Fig. 3b and Noah Phillips and Alissa Kotowski for providing photomicrographs in Fig. 4a and Fig. 4c, respectively. Thanks also go to Alissa Kotowski, Christie Rowe and Randy Williams for discussions and feedback on an early draft of the manuscript. This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), Discovery Grant RGPIN-2016-04677 (J.D.K.), the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme, Starting Grant agreement 715836 (A.F.) and the Earthquake Hazards Program of the U.S. Geological Survey (D.R.S.).
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Glossary
- Accretionary wedge
-
The accumulated rock scraped off the oceanic plate and transferred to the upper plate at subduction margins, forming a wedge shape in cross section.
- Tectonic tremor
-
Low-amplitude seismic signals defined by non-impulsive arrivals, similar to noise but distinguished by coherence over large geographic areas.
- Hypocentre
-
The point on a fault where an earthquake rupture starts.
- Frictional sliding
-
Displacement between two surfaces in contact, which is resisted by a shear stress proportional to the normal stress resolved on the surface.
- Diffusion creep
-
A grain-scale deformation mechanism in which grains accommodate strain by the diffusion of matter through or around grains.
- Crystal–plastic deformation
-
The intragranular deformation mechanisms that cause individual grains to change shape by dislocation-based mechanisms.
- Double-couple source mechanisms
-
Model that uses couples of point forces to describe the seismic wave radiation pattern for an earthquake whose displacement is within the plane of the fault.
- Critically stressed
-
When the shear stress resolved on a fault is just below the frictional strength of the fault, so that small perturbations to the stress field can cause failure.
- Dislocation motion
-
Used here to refer to deformation mechanisms that involve movement of dislocations, linear imperfections in the crystal lattice of grains, to accommodate strain.
- Dissolution–precipitation creep
-
A deformation mechanism by which grains change shape through dissolution at high-stress sites, accompanied by fluid-assisted diffusive mass transfer towards, and reprecipitation at, low-stress sites.
- Finite strain
-
The total strain, or change in shape, that has affected a rock.
- Cataclastic flow
-
A brittle process in which a volume of rock deforms by frictional sliding and grain rolling combined with fracture, causing an overall change in shape.
- Anastomosing
-
A geometry in which surfaces or strands diverge and rejoin; braided.
- Foliation
-
A rock fabric that can be approximated as a plane, often defined by the preferred orientation of mineral grains and/or by compositional banding.
- Ultramylonite
-
Very-fine-grained fault rock that deformed predominantly by plastic mechanisms.
- S-C-C′ composite fabrics
-
Composite fabrics that form inside shear zones (namely, by plastic deformation) — the S-foliation represents local shortening, while C and C′ foliations are small-scale shear bands.
- Composite fabrics
-
Foliation that is defined by more than one set of oriented fabrics in the rock, which form discrete sets.
- Boudinage
-
Process by which relatively competent layers split apart into smaller sections when stretched, and the surrounding, relatively incompetent, material deforms to accommodate the change in shape of the competent layer.
- Buckle folding
-
Folding that is inferred to form by layer-parallel shortening when relatively competent, or viscous, layers or features are surrounded by less competent rock.
- Mélange
-
Mixtures of rock types that are characterized by a block in matrix fabric, used here to refer to rock units that formed and deformed due to tectonic shearing.
- Pelitic rocks
-
Rocks that have a high clay content, or their metamorphic equivalents.
- Transposition
-
Process by which rotation of layers during folding or shearing causes the original orientation, angular relationships and distinct features of the layers in the rock to be almost completely obliterated.
- Imbrication
-
Process of thrust faulting that causes multiple, approximately parallel, slices of rock to be thrust on top of one another.
- Prograde deformation
-
Deformation that occurs while the rocks experience an increase in temperature and/or pressure, typically during burial (including subduction-related burial).
- Protoliths
-
The pre-deformation or pre-metamorphic equivalent of a deformed or metamorphosed rock.
- Dislocation creep
-
Intracrystalline deformation mechanism in which strain is accommodated by migration of dislocations, linear imperfections in the crystal lattice of grains, accompanied by dislocation climb.
- Cataclastic bands
-
Layers of fault rock in which the grain size is reduced owing to cataclastic processes when the layer accommodated shear displacement.
- Pseudotachylyte
-
The quenched remnants of a molten rock that formed by frictional heating on a fault surface during earthquake slip.
- Phyllosilicates
-
Minerals (including clays and micas) that are made up of stacks of parallel sheets of silicate tetrahedra, which are weakly bonded together.
- Extensional hydrofractures
-
Opening-mode cracks, formed when the pore fluid pressure exceeds the minimum compressive principal stress and the differential stress is less than twice the cohesion of the rock.
- En echelon
-
Describes the geometry of parallel or subparallel overlapping structures (usually opening-mode veins or faults) that are offset from one another in the direction perpendicular to their long axes, and are oblique to the overall structural trend.
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Kirkpatrick, J.D., Fagereng, Å. & Shelly, D.R. Geological constraints on the mechanisms of slow earthquakes. Nat Rev Earth Environ 2, 285–301 (2021). https://doi.org/10.1038/s43017-021-00148-w
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DOI: https://doi.org/10.1038/s43017-021-00148-w
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