The 2011 off the Pacific coast of Tohoku Earthquake and its aftershocks observed by GEONET

Abstract

The large displacement induced by the 2011 M 9.0 off the Pacific coast of Tohoku Earthquake was observed by GPS stations of the permanent GPS Earth Observation Network system (GEONET) in northeastern Japan. The displacement was characterized by the eastward displacement and subsidence in the Pacific coastal area. The horizontal displacement exceeded 5.3 m, which is the largest ever detected by GEONET. The mainshock was followed by a sequence of aftershocks. We processed the GPS data through a kinematic positioning strategy to clarify the deformation, including the deformation caused by the mainshock, with high temporal resolutions. The offsets calculated from the kinematic coordinates separately depict the coseismic displacements of the mainshock, the largest aftershock, and the third largest. The fault model for these earthquakes suggests that the largest (M 7.7) and third largest (M 7.3) aftershocks ruptured the southern and northern extensions of the mainshock fault, respectively.

Strain anomalies induced by the 2011 Tohoku Earthquake (M w 9.0) as observed by a dense GPS network in northeastern Japan

“…To confirm this, we calculated the SC-residual and SC-ratio using two slip models. One is a rectangular fault model with a uniform slip based on Nishimura et al (2011), which consists of five rectangular faults, including two large aftershocks which occurred immediately after the mainshock. The calculated SC-residual and SC-ratio is shown in Figs.…”

Coseismic and early postseismic slips associated with the 2011 off the Pacific coast of Tohoku Earthquake sequence: EOF analysis of GPS kinematic time series

“…In the case of the 2011 Tohoku-oki earthquake, Chang and Chao (2011) applied EOF analysis to the GPS kinematic time series obtained from GEONET and identified several modes corresponding to the coseismic, and postseismic, deformations. The purpose of this study is to expand the study of Nishimura et al (2011) to estimate slip distributions associated with the earthquakes and afterslip from the GPS kinematic time series to obtain insights into slip evolution and stress transfer. For this purpose, the study of Chang and Chao (2011) has been extended to extract a reliable deformation field associated with the earthquakes and afterslip from the EOF modes corresponding to the coseismic, and postseismic, deformations.…”

“…It is, therefore, necessary to enhance the signal-to-noise ratio of the GPS kinematic time series to extract the deformation field corresponding to each earthquake and to afterslip at the GPS observation sites; these data are needed to estimate the associated slip on the plate interface. Nishimura et al (2011) constructed fault models for the 2011 Tohoku-oki earthquake sequence using the GPS kinematic time series of the GEONET stations. They successfully estimated the fault models of the foreshock, mainshock, and the Sanriku-oki and Ibaraki-oki aftershocks.…”

Rupture process of the largest aftershock of the M 9 Tohoku-oki earthquake obtained from a back-projection approach using the MeSO-net data

“…However, we cannot comment on the magnitude of the slip there. Performing a nonlinear inversion using GPS data, Nishimura et al (2011) estimated 3.76 ± 0.5 m as the average amount of the slip on a rectangular fault that almost overlaps with the rupture area. If the radiated energy distribution (Fig.…”