ZHAO Shuxian;XU Shaoxie;MA Li;WU Pingjing;ZHANG Yongqing
It is not anywhere and anytime that large earthquakes can occur. Large earthquakes occur in their special temporal and spatial windows. The intersection between earthquake strip and earthquake circularity, the difference in seismic activities, the earthquakes in great depth and the events outside the Earth are the main factors that control the temporal and spatial windows of large earthquake occurrences. An earthquake of magnitude of 9.0 occurred on 11 March 2011, off the Pacific Coast of the northeastern part of the Japanese main land (Tohoku Region). Before the earthquake of M9.0, in Japan Trench subduction zone, the seismic activities showed some characteristic predictability signs: (1) quiescence area of the interplate earthquake of Mj≥7.0, since 1925, (2) the strip of earthquake of Mj≥7.0 perpendicular to Japan Trench since 2003 which begins with a deep earthquake and locates in the middle of the quiescence area, (3) generalized foreshocks of Mj≥5.6 occur in a limited local time period, not random in nature, since March 2009, and (4) foreshock (2011-03-09 Mj7.3) occurs in the quiescence area. The main shock occurred at the place where in the margin of the quiescence area, at the intersection of an earthquake strip perpendicular to Japan Trench and the arc-shaped interpolate earthquake zone in Japan Trench subduction zone, in the area with a distinct spatial variability in seismic activities. The fault surface of the main shock looks to match coplanarly with the fault surfaces of another two interplate earthquakes of Mj≥7.0 in the earthquake strip perpendicular to Japan Trench. The main shock occurs in the middle of the local time period in which generalized foreshocks occur frequently. Predictability patterns of the Tohoku earthquake of M9.0 in 2011 are very similar as our previously discovered ones.
