Fig. 1.
From: Variability of megathrust earthquakes in the world revealed by the 2011 Tohoku-oki Earthquake
Seismic activity in Japan and its vicinity. a: Seismic segmentation used in the official earthquake forecasting4 of the Evaluation of Major Subduction Zone Earthquakes by the Headquarters for Earthquake Research Promotion. The historically largest earthquake in each segment is indicated. b: Epicenters of earthquakes (yellow symbols classified by magnitude) from 1950 to 2010 with magnitudes given by Japan Meteorological Agency equal to, or larger than, 6.0 and focal depths equal to, or shallower than, 60 km. Trenches and troughs near Japan are illustrated by red curves. The 2011 Tohoku-oki megathrust earthquake ruptured the area circled by the solid ellipse, where along-dip double segmentation (ADDS) is obvious. Along-strike single segmentation (ASSS) can be found in the Nankai Trough, where little recent seismic activity has been observed. Such regions are often called seismic gaps. 4http://www.j-shis.bosai.go.jp/map/?lang=en (2010).