Fig. 4
From: Transition from collision to subduction and its relation to slab seismicity and plate coupling
a Epicentral distribution of earthquakes that occurred at 20–50 km depths (blue dots). For the plot, we used hypocentral data from the unified catalog of the Japan Meteorological Agency. Most of the events shown are intraslab earthquakes within the subducting Philippine Sea plate. The reflective zone also corresponds to the down-dip limit of slab seismicity. Major geological boundaries are shown by dashed lines, and the Itoigawa-Shizuoka Tectonic Line (ISTL) is highlighted by thick solid line. b Comparison of location of the reflective plate boundary with plate coupling. Blue curves indicate slip deficit rate from 1997 to 1999 (Suito and Ozawa 2009), and the outer and inner contour lines correspond to 20 and 30 mm/year, respectively. Note that the reflective zone we found is located at the down-dip end of the strongly coupled plate boundary