Skip to main content
Fig. 1 | Earth, Planets and Space

Fig. 1

From: Seismicity prior to the 2016 Kumamoto earthquakes

Fig. 1

a Map of b-values obtained from events from January 1, 2000, to April 14, 2016, 21:25 (immediately before the Kumamoto earthquakes). Overlapped on the map are the hypocenter (yellow star) and rupture zone (rectangle) of the M7.3 mainshock; M6.5-class foreshocks (red stars); M ≥ 5 foreshocks (squares); and M ≥ 5 aftershocks (circles). Triangles: volcanos; red line: faults. We calculated b-values (Woessner and Wiemer 2005) for events with depths 25 km or shallower falling in a cylindrical volume with radius R = 5 km, centered at each node on a 0.02º × 0.02º grid (we did not use a fixed number of earthquakes) and plotted a b-value at the corresponding node only if at least 50 events in the cylinder yielded a good fit to the GR law. b GR fitting is shown for points A, B, and C in a. c Plot of b-values as a function of time, as obtained from seismicity in the cylindrical volume with R = 10 km, centered at the mainshock. We used a moving window approach, whereby the window covered 500 events. Uncertainty estimates are according to Shi and Bolt (1982). Gray squares and open circles show the b-values obtained from foreshocks and aftershocks, respectively. Horizontal line regional average b = 0.93; vertical line moment of the mainshock

Back to article page