Fig. 5

Spatial distribution of focal mechanism solutions obtained in this study. Mechanisms with Quality A to D were plotted. All diagrams are equal area projection on the lower hemisphere of focal sphere. Colored areas show compressional quadrants. Note that the solutions with epicenters located within 5 km from the surface trace of the Atotsugawa fault are not plotted. The rectangle indicates the area shown in Fig. 6(a). Numbers labeled on each solution correspond to the event number of Table 1. Solutions in red indicate normal-fault type events with rakes from −140° to −40°. Solutions in blue indicate reverse-fault type events with rakes from +40° to +140°. Solutions in black show events with remaining range of rake. A bold line labeled as AF is the surface trace of Atotsugawa fault. Thin lines are the other active faults. The name of prefectures is indicated in rectangles, and red lines show their boundaries.