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Earth, Planets and Space
Fig. 3 | Earth, Planets and Space

Fig. 3

From: Spatio-temporal characteristics of frictional properties on the subducting Pacific Plate off the east of Tohoku district, Japan estimated from stress drops of small earthquakes

Fig. 3

a Stress drops for individual earthquakes estimated from P waves. The color and scale of circles express values of stress drop and earthquake magnitudes, respectively. The thick lines show the depth of the upper surface of the subducting Pacific Plate (Kita et al. 2010; Nakajima and Hasegawa 2006; Nakajima et al. 2009). Thin contours indicate the coseismic displacement of the 2011 Tohoku earthquake with \(M_W\)9.0 (Iinuma et al. 2012) at an interval of 2 m. b Spatially smoothed pattern of stress drop, which was derived from (a) at grid points at intervals of 0.1 degrees in latitude and longitude. Value at individual grid points were calculated as the average of stress drops of earthquakes within 20 km of the epicentral distance from the grid points. No values were assigned at grid points with less than four earthquakes within 20 km of the epicentral distance. c Values of stress drop obtained from S waves. d Spatially smoothed pattern of stress drop derived from (c). e Spatial pattern of the stress drop ratio derived from P and S waves. f The ratio of stress drops derived from P and S waves as a function of the values estimated from S waves

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