Fig. 1.

Seismicity in subduction zones of (a) Tohoku, eastern Japan, and (b) Alaska with fault areas of the 2011 and 1964 earthquakes in white, compiled by Tohoku University (after Uchida et al. (2009)) and the U.S. Geological Survey, respectively. In eastern Japan, earthquakes in 1980–2001 at depths shallower than 60 km are plotted. The segmentation of seismogenic zones are shown in (a), following the national project of disaster prevention of Japan (http://www.j-shis.bosai.go.jp/?lang-en). In Alaska, earthquakes before the 1964 earthquake of magnitude over 5.0 are plotted from 1935 to 1964 and magnitude over 4.5 from 1990 to 2010.