摘要：The 2011 Tohoku earthquake off the Pacific coast of Japan was the largest earthquake since the setup of a high-density seismic network in Japan.This network has recorded a change in seismicity patterns after the Tohoku earthquake, with seismicity increasing in a number of areas, including the southeast of the Tohoku region.Here, we present new research into shear-wave splitting during crustal earthquakes within this area of newly-activated seismicity by comparing shear-wave splitting before and after the 2011 event.In the pre-2011 Tohoku earthquake dataset, polarization azimuths within the area of newly-activated seismicity and the region immediately surrounding this area were almost NNE-SSW and ESE-WNW, respectively.Post-2011 Tohoku earthquake data in the same area also records a NNE-SSW polarization azimuth direction.Data with an ESE-WNW polarization azimuth most probably relate to the regional stress field in the area associated with the westward subduction of the Pacific Plate; however, data from the area of seismicity-activated with NNE-SSW polarization azimuths are inconsistent with the expected regional stress field.Our shear-wave splitting analysis suggests that the orientation of the maximum stress axis in the area that underwent activation in seismicity did not change significantly after the 2011 Tohoku earthquake. Key words Shear-wave splitting activated seismicity 2011 Tohoku earthquake polarization azimuth.
