Earth Planets Space, Vol. 63 (No. 7), pp. 631-636, 2011
Takuya Nishimura, Hiroshi Munekane, and Hiroshi Yarai
Geospatial Information Authority of Japan, Kitasato 1, Tsukuba, Ibaraki 305-0811, Japan
(Received April 12, 2011; Revised June 15, 2011; Accepted June 16, 2011; Online published September 27, 2011)
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.
Key words: Kinematic GPS, 2011 Tohoku earthquake, mainshock, aftershock, coseismic deformation.