Fig. 2
From: Stress loading and the occurrence of normal-type earthquakes under Boso Peninsula, Japan
a, b Focal mechanisms for earthquakes distributed in PHS and EUR plates, from 2003/1/1 to 2019/9/30. Solid and dashed contours denote upper surface of PHS and PAC plates, respectively. c, d Earthquake mechanisms from PHS and EUR before and after M9 Tohoku earthquake of 2011/03/11, in vertical section. Mechanisms outlined in black, red, and blue denote three groups: (A) major intraplate earthquakes, (B) interplate earthquakes, thrust-type, and (C) anomalous intraplate earthquakes, thrust-type. Range for plots in (c) and (d) marked as shaded strips in panels (a) and (b). All earthquakes from NIED F-net catalog. Focal mechanisms color-keyed to fault types, expressed as normalized mean horizontal moment tensor τ′m. Frequency distribution of τ′m displayed in histogram. n = total number of earthquakes