A fault model of the 2000 Tottori-ken Seibu earthquake

Haruo Horikawa, Haruko Sekiguchi, Tomotaka Iwata and Yuichi Sugiyama

We investigated the characteristics of the 2000 Tottori-ken Seibu earthquake, using strong motion data and leveling data. Five faults were assumed on the basis of detailed analyses of the aftershock distribution (Fig. 1 , Fig. 2). Inversion of the strong motion data with the multiple time window method revealed two asperities (patches of large slip, Fig. 3 , Fig. 4 , Fig. 5). The larger asperity is shallow and to the southeast of the hypocenter, extending over two faults. The smaller asperity is located at the deep part of the northernmost fault. However, the depth of the larger asperity is somewhat ambiguous. Analysis of leveling data suggests that the southernmost fault does not reach the ground surface and the upper edge of the fault is about 1 km deep (Fig. 6 , Fig. 7). Another characteristic of the event is a distinct initial rupture stage. The rupture area during the initial stage covers the region of swarm activities prior to the 2000 event (Fig. 8).