Results of tomographic inversion. Map showing Q
-1 at depths of (a) 20, (b) 30, (c) 40, (d) 50, (e) 60, and (f) 70 km. The color scale is shown at the bottom. Red triangles represent active volcanoes. White stars and gray dots represent small repeating earthquakes (Uchida et al. 2009) and other earthquakes, respectively, that occurred within 5 km of each depth slice. Earthquakes (M ≥ 2) that occurred from 2001 to 2012 are represented by gray dots. Dashed and black lines show the iso-depth contours of the Philippine Sea and Pacific slabs, respectively, at each corresponding depth. Only the regions with hit counts of >100 are shown.