Crustal movements of the eastern Honshu offshore M_S7.2 earthquake in Japan in 2016

In Japan, on November 22, 2016, occurred the eastern Honshu offshore M_S7.2 earthquake, which was the aftershock of the 2011 Tohoku M_W9.0 earthquake. Time series of coordinates of a large number of GPS stations in the world are available at the website of the Nevada Geodetic Laboratory of the Nevada University. Based on the time series of coordinates in the global reference frame of IGS08 at more than 30 stations of continuous GPS observations, downloaded from the website and with the station of continuous GPS observation BJSH near Beijing used as the core station in the regional reference frame, the coseismic displacements and time series of horizontal displacements before and after the earthquake are analyzed in time and space. The results show, though the eastern Honshu offshore M_S7.2 earthquake, as the aftershock of the 2011 Tohoku M_W9.0 earthquake, was intensely affected by the postseismic crustal deformation of the main shock, the precursory horizontal deformations were in good agreement with those of other large earthquakes. The prominent feature of the Tohoku earthquake is that there was no significant preseismic vertical displacement accumulation, whereas the vertical displacements before and after the eastern Honshu offshore M_S7.2 earthquake show slow and uniform decaying as those after the main shock. Shortly before the earthquake, the stations of continuous GPS observations near the epicenter showed significant decrease in velocities or even zero as for the east component, which were short term precursory anomalies. Moreover, two types of coseismic displacements and their cause were discussed, and the horizontal compression in the crust was the cause of the aftershock.