A self‐consistent mechanism for slow dynamic deformation and tsunami generation for earthquakes in the shallow subduction zone

Abstract

Dynamic pore pressure changes in the overriding wedge above a shallow‐dipping plate interface significantly affect the rupture dynamics of shallow subduction zone earthquakes and their tsunamigenesis. For a wedge on the verge of Coulomb failure everywhere including the basal fault, the dynamic pore pressure increase due to up‐dip rupture propagation leads to widespread yielding within the wedge, which is greatly enhanced by the shallow dip of the fault. The widespread yielding reduces the stress drop, slip velocity, slip, and rupture velocity, giving rise to prolonged rupture duration, thus explaining many anomalous features of shallow subduction zone earthquakes. Significant inelastic seafloor uplift occurs in the case of a shallow fault dip, with the largest uplift located landward from the trench. Integrating this physical mechanism with existing seismic, geodetic, and tsunami observations can provide new insights into earthquake dynamics and deformation processes in shallow subduction zones.

Compressive sensing of frequency-dependent seismic radiation from subduction zone megathrust ruptures

“…It is well known that shallower earthquakes in subduction zones, in particular tsunami earthquakes, have significantly longer source durations and depleted short-period energy (5,21,22). This is consistent with slower rupture propagation of tsunami earthquakes caused by soft low-rigidity sediments on the shallow plate interface (5,22) and possibly the increase of dynamic pore pressure in the shallow up-dip region (23).…”

“…This implies that these megathrust earthquakes rupture more slowly and continuously in a large area in the up-dip region to generate LF seismic radiation along the shallower portion of the subduction plate interface. The slower rupture speed and prolonged rupture duration in the up-dip region are probably caused by the low rigidity of the fault material, e.g., subducted sediments (22,34), and the increase of dynamic pore fluid pressure (5,23 For the Tohoku, Maule, and 2005 Sumatra earthquakes, there is a systematic lack of early aftershocks in the shallow up-dip region (e.g., above 15 km) and the early aftershock rate is also very low deeper than 35 km (Figs. 5 A-C), although the depth range of aftershocks for each event appears different.…”

Simple Crack Models Explain Deformation Induced by Subduction Zone Megathrust Earthquakes

“…Such a compressional feature can be greatly enhanced as the rupture front approaches the trench, because the ruptureinduced stress change generally scales with the rupture zone dimension (Fig. 9a,b), free-surface effects become more prominent, and triggered failure around the rupture front has more opportunity to reach the surface (Rosenau and Oncken, 2009;Ma, 2012). These transient features arising in dynamic rupture models are not present in the dynamic critical taper model (which is actually a quasi-static model).…”

Extreme scale multi-physics simulations of the tsunamigenic 2004 sumatra megathrust earthquake

“…First, we already produced a similar scenario without splay faults; coupling this seafloor displacement with additional tsunami models will highlight the role of splay faults in producing a large tsunami wave. Furthermore, 2D dynamic rupture simulations [62,64] on planar dipping faults show that plastic deformation in the overriding wedge results in a distinct, more vertical seafloor uplift, which might enhance the tsunami caused by the earthquake. Incorporating off-fault plasticity is computationally challenging and would increase computational time by up to 50 % [75].…”

“…Furthermore, if a rupture front breaks the surface, it strongly excites seismic waves [7] and interacts with reflected waves from the free surface [46] across the uppermost parts of the fault system. Few dynamic rupture models have tackled subduction zone earthquakes so far, and most of these use simplified fault planes dipping at large angles [24,46,62,85]. Studies investigating the effect of more realistic geometries on shallow slip and seafloor displacement were restricted to 2D [53].…”