SEISMIC ACTIVITY CHANGE PRECEDING THE SUMATRA GIANT EARTHQUAKE SERIES, 2004M9.0, 2005M8.6, AND 2007M8.5

摘要

The seismicity along the Sunda trench was examined from the viewpoint of whether or not any significant change preceded the major earthquakes. Based on the seismicity of M5 and greater earthquakes, a growth of activated zones with time approaching the final breakage was detected. These activated zones well predicted the positions of the real asperities for the following 2004 M9.0, 2005 M8.6, and 2007 M8.5 events. Such a feature in seismicity change can be explained by introducing an assumption that a quasi-static slip progressed on a weakly locked plate boundary prior to the final breakage, and resulted in an activation corresponding to the induced stress concentration. At present, there are two activated zones unresolved. Accepting the limit in validity of the above hypothesis, I would like to give warnings for imminent earthquake occurrences in these zones.