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Progress in Earth and Planetary Science
Fig. 4 | Progress in Earth and Planetary Science

Fig. 4

From: Spatial pattern in stress drops of moderate-sized earthquakes on the Pacific Plate off the south-east of Hokkaido, Japan: implications for the heterogeneity of frictional properties

Fig. 4

a Stress drops for individual earthquakes estimated from P waves. The scale and color of circles indicate the earthquake magnitude and value of stress drop, respectively. The thick lines indicate the depth of the upper surface of the subducting Pacific Plate (Kita et al. 2010). Thin contours A through C show coseismic displacements for the 1968 Tokachi-oki (Nagai et al. 2001), 2003 Tokachi-oki (Yamanaka and Kikuchi 2003), and 1973 Nemuro-oki earthquakes (Yamanaka 2006), respectively, at intervals of 1 m. b Spatially smoothed stress drop derived from (a) at grid points at intervals of 0.1 degrees in latitude and longitude. The value at each grid point was calculated as the average of stress drops of earthquakes within 20 km of the epicentral distance from the grid point. Values were not assigned at grid points with less than four earthquakes within 20 km of the epicentral distance. c Stress drops estimated from S waves. d Map view of spatially smoothed stress drop derived from (c)

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