Spatio-temporal distribution of seismic moment release near the source area of the 2011 Tohoku-Oki earthquake

Abstract

To understand the generation mechanism of the 2011 Tohoku-Oki earthquake, we analyzed the spatial and temporal distribution of the cumulative seismic moment ( M 0 ) for all earthquakes along the Japan Trench listed in the global centroid moment tensor catalog between January 1976 and November 2011. Three areas with distinct characteristics of M 0 are identified: (1) in the 2011 Tohoku-Oki source area, the M 0 released in the down-dip portion (≥30 km) was greater than that in the up-dip portion (<30 km) before the mainshock; (2) the M 0 of the up-dip portion in the region where slow slip activity prevails is greater than that of the down-dip portion throughout the study period; (3) in the surroundings of the source area, where interplate coupling is relatively low and the largest foreshock occurred, values of M 0 for the down-dip and up-dip portions are both intermediate. Our results show that a megathrust rupture could be generated by large accumulations of strain energy at the subduction interface, resulting from the differential strain energy released in the down-dip and updip portions during the interseismic interval. We propose that the variation pattern of M 0 may offer spatial constraints for seismic hazard assessment in the future.

A holistic seismotectonic model of Delhi region

“…The spatial variation of energy release can provide information on the potential locales of stress accumulation in a region in the absence of geodetic data. Similarly, the temporal variation of seismic energy of a region can provide the different stages of energy release process 42 , 51 and could be used as a long-term earthquake precursor. In the present study, the spatial distribution of strain energy has been estimated for Delhi and the surrounding areas based on the earthquake catalog of the region for the period 1998-2020 taken from the website of National Centre for Seismology ( https://seismo.gov.in/content/seismological-data ).…”

“…The energy released in the last two decades also indicates a similar focal mechanism. Shukla 46 through FPS of 10 earthquakes (of 2001–2004, with single component seismographs) and Bansal and Verma 51 through FPS of 01 earthquake recorded with digital strong motion data have suggested DSR, bounded by reverse fault/thrust is an NW–SE trending structure. The fault plane solutions of the two earthquakes (29th May 2011 and 01st June 2017) fallen close to DSR have also shown reverse/thrust faulting with strike slip mechanism.…”

Rupture‐Depth‐Varying Seismicity Patterns for Major and Great (Mw ≥ 7.0) Megathrust Earthquakes

“…To evaluate changes in moment rates of different categories of events, we compute ratios of the seismic moment rates of short‐term and long‐term aftershocks to the background rates of similar category activity, denoting these as “normalized moment rates.” The normalization emphasizes the perturbation in seismicity caused by the mainshock strain drop and induced stress changes (e.g., Lin & Wu, ). Figure S4 shows the normalized moment rates for interplate and intraplate aftershocks, grouped by whether the mainshock ruptures Domain A or Domain B.…”