The frictional, hydrologic, metamorphic and thermal habitat of shallow slow earthquakes

Saffer, D. M.; Wallace, Laura

doi:10.1038/ngeo2490

Cited by 259 publications

(333 citation statements)

References 52 publications

(147 reference statements)

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“…These were also initially observed in the vicinity of the deepest portions of the seismogenic zone (Fig. 15), but more recent observations indicate that shallower megathrust SSEs occur as well (Saffer and Wallace, 2015, and references therein), including very close to the trench (Araki et al, 2017).…”

Section: Spectrum Of Slip Velocitiesmentioning

confidence: 96%

“…Aseismic slip triggered by great earthquakes is also common (e.g., Chlieh et al, 2007;Hsu et al, 2006;Ozawa et al, 2011;Hayes et al, 2014a;Uchida et al, 2015). Aseismic, or slow-slip, transients are not limited to regions of recent great earthquakes, as these have Bilek and Lay | Subduction zone megathrust earthquakes GEOSPHERE | Volume 14 | Number 4 been observed in both shallow and deep portions of the seismogenic zone in many subduction zones around the globe (e.g., Dragert et al, 2001;Obara et al, 2004;Schwartz and Rokosky, 2007;Correa-Mora et al, 2009;Jiang et al, 2012;Saffer and Wallace, 2015;Wallace et al, 2016).…”

Section: Spatial Variations Of Slipmentioning

confidence: 99%

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Subduction zone megathrust earthquakes

2018

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Subduction zone megathrust faults host Earth's largest earthquakes, along with multitudes of smaller events that contribute to plate convergence. An understanding of the faulting behavior of megathrusts is central to seismic and tsunami hazard assessment around subduction zone margins. Cumulative sliding displacement across each megathrust, which extends from the trench to the downdip transition to interplate ductile deformation, is accommodated by a combination of rapid stick-slip earthquakes, episodic slow-slip events, and quasi-static creep. Megathrust faults have heterogeneous frictional properties that contribute to earthquake diversity, which is considered here in terms of regional variations in maximum recorded magnitudes, Gutenberg-Richter b values, earthquake productivity, and cumulative seismic moment depth distributions for the major subduction zones. Great earthquakes on megathrusts occur in irregular cycles of interseismic strain accumulation, foreshock activity, main-shock rupture, postseismic slip, viscoelastic relaxation, and fault healing, with all stages now being captured by geophysical monitoring. Observations of depth-dependent radiation characteristics, large earthquake slip distributions, variations in rupture velocities, radiated energy and stress drop, and relationships to aftershock distributions and afterslip are discussed. Seismic sequences for very large events have some degree of regularity within subduction zone segments, but this can be complicated by supercycles of intermittent huge ruptures that traverse segment boundaries. Factors influencing variability of large megathrust ruptures, such as large-scale plate structure and kinematics, presence of sediments and fluids, lower-plate bathymetric roughness, and upper-plate structure, are discussed. The diversity of megathrust failure processes presents a suite of natural hazards, including earthquake shaking, submarine slumping, and tsunami generation. Improved monitoring of the offshore environment is needed to better quantify and mitigate the threats posed by megathrust earthquakes globally.

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Section: Spectrum Of Slip Velocitiesmentioning

confidence: 96%

Section: Spatial Variations Of Slipmentioning

confidence: 99%

Subduction zone megathrust earthquakes

2018

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“…Although initial studies focused on subduction zones where young and warm plates are being subducted beneath a continental margin, episodic slow slip and/or tremor events were later recognized in various other subduction zones, in the shallow part of the megathrust fault near the trench (Saffer and Wallace, 2015, and references therein) as well as in the deeper parts of strikeslip faults (e.g., Nadeau and Dolenc, 2005). In this paper we refer to episodic slow fault rupture events (with either or both documented slow slip and tremor) as slow earthquakes, and focus on the main deep subduction zone slow earthquakes, i.e.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review

2016

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More than a decade after the discovery of deep episodic slow slip and tremor, or slow earthquakes, at subduction zones, much research has been carried out to investigate the structural and seismic properties of the environment in which they occur. Slow earthquakes generally occur on the megathrust fault some distance downdip of the great earthquake seismogenic zone in the vicinity of the mantle wedge corner, where three major structural elements are in contact: the subducting oceanic crust, the overriding forearc crust and the continental mantle. In this region, thermo-petrological models predict significant fluid production from the dehydrating oceanic crust and mantle due to prograde metamorphic reactions, and their consumption by hydrating the mantle wedge. These fluids are expected to affect the dynamic stability of the megathrust fault and enable slow slip by increasing pore-fluid pressure and/or reducing friction in fault gouges.Resolving the fine-scale structure of the deep megathrust fault and the in situ distribution of fluids where slow earthquakes occur is challenging, and most advances have been made using A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTteleseismic scattering techniques (e.g., receiver functions). In this paper we review the teleseismic structure of six well-studied subduction zones (three hot, i.e., Cascadia, southwest Japan, central Mexico, and three cool, i.e., Costa Rica, Alaska, and Hikurangi) that exhibit slow earthquake processes and discuss the evidence of structural and geological controls on the slow earthquake behavior. We conclude that changes in the mechanical properties of geological materials downdip of the seismogenic zone play a dominant role in controlling slow earthquake behavior, and that near-lithostatic pore-fluid pressures near the megathrust fault may be a necessary but insufficient condition for their occurrence.

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“…Alternatively, the reflectors may occur within altered basaltic lavas and volcaniclastic sediments. If the former interpretation is correct, then the correlation between HRZ and a subset of the SSEs would support the idea that fluid pressure plays a key role in the generation of slow slip by reducing effective stress (e.g., Kodaira et al, 2004;Liu and Rice, 2007;Audet et al, 2009;Song et al, 2009;Saffer and Wallace, 2015).…”

Section: Geological Settingmentioning

confidence: 77%

“…The key foci for postexpedition studies on core samples include (but are not limited to) (1) structural analysis of fractures and faults to define deformation behavior, style, and orientations (e.g., Byrne et al, 2009); (2) studies of fault and wall rock rheology and friction to test hypotheses linking fault constitutive properties to slip behavior (e.g., Saffer and Wallace, 2015;Leeman et al, 2016); (3) geomechanical measurements to define poroelastic and strength properties of the formation to guide interpretation of observatory data as described above for proposed Site HSM-01A (e.g., ; and (4) measurements of strength, permeability, and elastic moduli to provide context for the interpretation of borehole failures as indicators of in situ stress magnitude, parameterization of hydrological models, and core-log-seismic integration.…”

Section: Frontal Thrust Sitementioning

confidence: 99%

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2017

International Ocean Discovery Program Scientific Prospectus

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The frictional, hydrologic, metamorphic and thermal habitat of shallow slow earthquakes

Cited by 259 publications

References 52 publications

Subduction zone megathrust earthquakes

Subduction zone megathrust earthquakes

Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review

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