VARIATION IN SOURCE CHARACTERISTICS OF REPEATING M6-CLASS PLATE-BOUNDARY EARTHQUAKES OFF KESENNUMA, NORTHEAST JAPAN

Abstract

Nowadays, the scenario-based strong motion prediction is strongly required quantitatively to show its diversity and uncertainty. We focus on the variation or uncertainty in source parameters such as the size and stress drop of the strong motion generation area (SMGA). Repeating M6-class plate-boundary earthquakes occurring off Kesennuma, northeast Japan, were analyzed. The latest event on May 13, 2015 (MJMA 6.8) had two SMGAs, and each event in 1973, 1986 and 2002 had one SMGA. The SMGA1 of the 2015 event and SMGAs of the other three events were close to each other in space, and their spatial extent was almost same. The variation in the estimated stress drop of SMGA was approximately less than 1.6 times of the smallest event.