Reconciling the conflicting extent of overriding plate deformation before and during megathrust earthquakes in South America, Southeast Asia, and Japan

Abstract

We aim to better understand the overriding plate deformation during the megathrust earthquake cycle. We estimate the spatial patterns of interseismic GNSS velocities in South America, Southeast Asia, and northern Japan and the associated uncertainties due to data gaps and velocity uncertainties. The interseismic velocities with respect to the overriding plate generally decrease with distance from the trench with a steep gradient up to a "hurdle", beyond which the gradient is distinctly lower and velocities are small. The hurdle is located 500-1000 km away from the trench, for the trench-perpendicular velocity component, and either at the same distance or closer for the trench-parallel component. Significant coseismic displacements were observed beyond these hurdles during the 2010 Maule, 2004 Sumatra-Andaman, and 2011 Tohoku earthquakes. We hypothesize that

How Long Can the Postseismic and Interseismic Phases of Great Subduction Earthquake Sustain? Toward an Integrated Earthquake‐Cycle Perspective

“…For the convenience of discussion in this paper, following the concept of prolonged postseismic phase, and similar to Sun et al. (2018), we semantically define the apparent finishing time of the postseismic phase ( t B ) as the dividing boundary pass through the trench distance of 16 H (about 500 km), which is representative of the backarc region globally and is roughly the maximum distance of observable interseismic deformation (D'Acquisto et al., 2022; McKenzie et al., 2022). At this time, the surface deformation pattern is mostly wholesale landward and hence it is also stated as the beginning time of the interseismic phase.…”