Figure 2
From: Could a Sumatra-like megathrust earthquake occur in the south Ryukyu subduction zone?
Focal mechanisms of the thrust-type earthquakes extracted from the Global CMT catalog. (a) Along the Sumatra subduction system from 1976 to 25 December 2004 and (c) along the Ryukyu subduction system from 1976 to December 31, 2011 are shown. Deep blue beach balls show focal mechanisms. Co-seismic slip contours every 5 m of the 2004 great Sumatra earthquake shown in pink in (a) are from Chlieh et al. (2007). Pink light areas show the aseismic zones. (b, d) The free-air gravity anomaly. Purple dashed contours show the high free-air gravity anomalies in the fore-arc areas. The letter ‘S’ shows the possible mainshock area if a Sumatra-like earthquake were to occur in the Ryukyu fore-arc. The black focal mechanisms in (a) and (b) show the positions of the 2004 and 2005 mainshocks.