Fig. 1

Maps showing the study area location. The red star indicates the epicenter of the 2011 Tohoku-oki earthquake (M_w 9.0). Elevation data are from the ETOPO1 global relief model (NOAA 2009). a The open red rectangle indicates the area shown in b, and the yellow circle shows the location of the Kakioka Geomagnetic Observatory. b Green diamonds denote OBEM stations. The 2D models were constructed along the thick orange line. The yellow diamond indicates the JFAST borehole site (Chester et al. 2013). The red contours (10 m interval) show the fault slip during the 2011 Tohoku-oki earthquake based on (Iinuma et al. 2012)