Crustal earthquake S-wave polarization data for earthquakes shown in Fig. 2. Polarization azimuths and time delays between maximum and minimum phases are indicated by bar direction and length, respectively. Data are plotted at the location of the seismic station from which they were obtained, with shear-wave splitting data of earthquakes before and after the 2011 Tohoku earthquake shown in (a) and (b), respectively. The inset shows the orientations of the maximum stress axes (Kaneshima, 1990).