TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 64 (No. 12), pp. 1067-1075, 2012

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

Jing-Yi Lin1 and Wen-Nan Wu2

1Institute of Geophysics and Department of Earth Sciences, National Central University, 300 Jhongda Road, Jhongli City, Taoyuan County 32001, Taiwan
2Institute of Earth Sciences, Academia Sinica, Nankang, Taipei 11529, Taiwan

(Received December 29, 2011; Revised March 16, 2012; Accepted April 9, 2012; Online published January 28, 2013)

Abstract: To understand the generation mechanism of the 2011 Tohoku-Oki earthquake, we analyzed the spatial and temporal distribution of the cumulative seismic moment (ΣM0) 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 ΣM0 are identified: (1) in the 2011 Tohoku-Oki source area, the ΣM0 released in the down-dip portion (≥30 km) was greater than that in the up-dip portion (<30 km) before the mainshock; (2) the ΣM0 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 ΣM0 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 up-dip portions during the interseismic interval. We propose that the variation pattern of ΣM0 may offer spatial constraints for seismic hazard assessment in the future.
Key words: Seismic moment, Tohoku earthquake, seismogenic zone, Japan Trench.

Corresponding author E-mail: jylin@ncu.edu.tw

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