Interplate fault slip along the Japan Trench before the occurrence of the 2011 off the Pacific coast of Tohoku Earthquake as inferred from GPS data

Hisashi Suito,Mikio Tobita,Tetsuro Imakiire,Shinzaburo Ozawa,Takuya Nishimura

doi:10.5047/eps.2011.06.053

Hisashi Suito, Mikio Tobita + Show 3 more

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https://doi.org/10.5047/eps.2011.06.053

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Abstract

A sequence of M 7-class interplate earthquakes and transient postseismic slips following each of these earthquakes occurred along the Japan Trench before the occurrence of the giant earthquake on March 11, 2011. Continuous GPS data detected a significant postseismic deformation with displacements that were much larger than that of the coseismic offset. Moreover, the geodetic inversion results using these observations revealed that the total moment released by these transient slips was much larger than the coseismic ones. This differs from our understanding of the postseismic process that the postseismic deformation and slip are smaller than the coseismic ones. These transient processes may help us understand not only the postseismic process but also the pre-seismic signals indicating the occurrence of the giant earthquake.

Highlights

A giant earthquake with a moment magnitude of 9.0 occurred at 14:46 (JST) on March 11, 2011, along the Japan Trench (Fig. 1(a))
Its duration seems to be about 2 years, as Miura et al (2006) reported. We refer to this event as a reference of postseismic deformation produced by an afterslip in this study
A number of studies have reported that the postseismic signals produced by an afterslip rapidly decay with time and the amount of displacement is less than or equal to the coseismic offset, the decay time and duration of the signal are different for each earthquake and may depend on its mechanisms (e.g., Heki et al, 1997; Gahalaut et al, 2008; Perfettini et al, 2010)

Summary

Introduction

A giant earthquake with a moment magnitude of 9.0 occurred at 14:46 (JST) on March 11, 2011, along the Japan Trench (Fig. 1(a)). The time series of the GPS data in the east-west component clearly reveals coseismic offset and subsequent transient deformation at each earthquake (Fig. 1(b)). Based on these time series, we look into the spatial distribution of each coseismic and postseismic deformation (Fig. 2).

Results

Conclusion