Structural control and system-level behavior of the seismic cycle at the Nankai Trough

Shi, Qibin; Barbot, Sylvain; Wei, Sui; Tapponnier, Paul; Matsuzawa, Takanori; Shibazaki, Bunichiro

doi:10.1186/s40623-020-1145-0

Cited by 39 publications

(33 citation statements)

References 295 publications

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“…It is possible that the deep ruptures propagate into nominally slow‐slip or velocity‐strengthening regions, reducing their average potency density in the process. This may explain why no periodic slow‐slip has been found at subduction zones where a deep rupture recently took place, such as at the Japan trench (Agata et al, 2019; Muto et al, 2019) or the Sunda Trench (Hoechner et al, 2011), as the exceedingly large stress reduction caused by a large rupture may have interrupted the slow‐slip cycle for a few decades (Feng et al, 2015; Herrendörfer et al, 2015; Shi et al, 2020). The low potency density of deep megathrust ruptures may also be caused by their proximity to the stability transition zone, which may manifest itself by a gradual reduction of coseismic weakening with increasing temperature before stable‐weakening or firmly velocity‐strengthening properties are attained at greater depths.…”

Section: Discussionmentioning

confidence: 99%

Static Source Properties of Slow and Fast Earthquakes

2020

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The source characteristics of slow and fast earthquakes provide a window into the mechanical properties of faults. In particular, the average stress drop controls the evolution of friction, fault slip, and event magnitude. However, this important source property is typically inferred from the analysis of seismic waves and is subject to many epistemic uncertainties. Here, we investigate the source properties of 53 earthquakes and 17 slow-slip events on thrust and strike-slip faults in various tectonic settings using slip distributions constrained by geodesy in combination with other data. We determine the width, potency, and potency density of slow and fast earthquake sources based on static slip distributions. The potency density, defined conceptually as the ratio of average slip to rupture radius, is a measure of anelastic deformation with limited bias from rigidity differences across depths and tectonic settings. Strike-slip earthquakes have the highest potency density, varying from 20 to 500 microstrain. The potency density is on average lower on continental thrust faults and megathrusts, from 10 to 200 microstrain, with an algebraic decrease with centroid depth, indicative of systematic changes in dominant rupture processes with depth. Slow slip events represent an end-member style of rupture with low potency density and large rupture width. Significant variability in potency density of slow-slip events affects their moment-duration scaling. The variations of source properties across tectonic settings, depth, and rupture styles can be used to better constrain numerical simulations of seismicity and to assess the source characteristics of future earthquakes and slow slip events. Plain Language Summary Natural earthquakes reduce the stress that accumulates on faults due to plate tectonics. To better understand the variability of seismic hazards around active faults, we survey the properties of slow and fast earthquakes around the world. The potential of faults to concentrate large slip in the rupture area differs depending on the geological setting, the depth of the source, and the type of rupture. Earthquakes in a continental setting condense more slip in a given rupture area, particularly in transform faults like the San Andreas fault. Subduction zone earthquakes, although some of the largest events on Earth, generally distribute less slip over a wider area, but this varies as a function of depth. Slow earthquakes represent an extreme case of little slip distributed over a large area. The propensity of rupture characteristics to vary with fault type and depth may help forecast the hazards posed by future seismicity.

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Section: Discussionmentioning

confidence: 99%

Static Source Properties of Slow and Fast Earthquakes

2020

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“…We simulate the dynamics of fault slip and viscoelastic flow during the seismic cycle with the integral method (Lambert and Barbot 2016;Barbot 2018b;Shi et al 2020). The approach extends the boundary integral method to include both surface and volume elements.…”

Section: Numerical Solution With the Integral Methodsmentioning

confidence: 99%

“…The seismic cycle along the Nankai trough is characterized by a down-dip segmentation of rupture styles with slow-slip events, low-frequency earthquakes, and large ruptures that is typically persistent along strike (Hirose et al 2010;Obara and Kato 2016;Gao and Wang 2017). The dynamics of the seismic cycle at the Nankai trough is discussed in a companion paper in the same volume (Shi et al 2020). The Japan trench was the epicenter of the 2011 moment-magnitude (Mw) 9.1 Tohoku mega-quake that ruptured the megathrust up to the surface, generating a giant tsunami (Tajima et al 2013;Satriano et al 2014;Lay 2018).…”

Section: Introductionmentioning

confidence: 99%

Frictional and structural controls of seismic super-cycles at the Japan trench

Barbot

2020

Earth Planets Space

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The diverse mechanical behaviors of subduction zones during the seismic cycle emerge from the nonlinear dynamics of a complex mechanical system with interacting brittle and ductile deformation. The 2011 Tohoku mega-quake represents the culmination of a super-cycle of partial and full ruptures of the plate interface, but the physical controls on the down-dip segmentation of the megathrust remain unclear. Here, we propose a two-dimensional rheological model of the Japan trench to explain the variability of earthquake size at the Miyagi section, in northern Honshu, during the last century. We simulate seismicity in a continuum with a physics-based rate-and state-dependent constitutive law for fault slip, producing aperiodic earthquake sequences with a power-law distribution of rupture sizes. Although some partial ruptures of the megathrust are the result of self-emergent behavior, others are structurally controlled. The 1978 and 2005 Mj∼ 7 interplate earthquakes took place in a metamorphic belt in the mantle wedge corner bounded up-dip by the arc Moho that constitutes a permanent structural boundary. We explain the succession of the great 1981 Mw = 7.1 and 2003 Mw = 6.9 earthquakes within the forearc and the 2011 giant earthquake as the natural response of a large continuously velocity-weakening fault with a small nucleation size. The shallow segment below the frontal prism only slips in giant through-going ruptures that unzip the whole velocity-weakening interface. The model consistently explains the size, recurrence time, and hypocenter location of historical earthquakes in the Miyagi segment, the slow-slip and foreshock preparatory phase of the 2011 Tohoku earthquake, the large slip near the trench during the giant rupture, and important features of its postseismic deformation. The complex patterns of seismicity at the Japan trench can be better understood by assimilating geological and geophysical observations at various periods of the seismic cycle within an explicative physical framework.

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“…For R u > 17, the cycles include full and partial ruptures of the velocity-weakening region (e.g., Michel et al, 2017). Other work has focused on seismic cycles on faults with interacting asperities (Dublanchet et al, 2013;Kato, 2016;Lui & Lapusta, 2016;Mitsui, 2018;Shi et al, 2020). Here, we consider nonplanar faults and explore the effects of friction, fault geometry, and spatially variable loading rates for a fault-bend-fold system.…”

Section: Controls On Fault Dynamicsmentioning

confidence: 99%

Earthquake Cycles in Fault‐Bend Folds

2020

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In fold‐and‐thrust belts and accretionary prisms, fault bends induce folding in the hanging wall that can alter the long‐term loading rate on the megathrust and profoundly influence earthquake‐related processes. To understand the impact of nonplanar faults and off‐fault deformation on the seismic cycle, we incorporate fault‐bend fold theory into fault dynamics and develop two‐dimensional numerical simulations of slip evolution under a physics‐based rate‐ and state‐dependent friction law. Fault bends can play an important role in earthquake segmentation as a result of nonlinear fault dynamics, affecting the initiation and termination of earthquakes and the details of long‐term interseismic behavior. Shallow earthquakes that initiate, propagate, and terminate near the surface are facilitated when the stratigraphy within incoming thrust sheets is not parallel to the underlying fault, as this can change the loading rate across the fault bend.

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Structural control and system-level behavior of the seismic cycle at the Nankai Trough

Cited by 39 publications

References 295 publications

Static Source Properties of Slow and Fast Earthquakes

Static Source Properties of Slow and Fast Earthquakes

Frictional and structural controls of seismic super-cycles at the Japan trench

Earthquake Cycles in Fault‐Bend Folds

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