HR: 0800h
AN: T21B-0580    [Abstracts]
TI: Transitional pattern of stress field between Honshu arc and Ryukyu arc in Japan revealed by the multiple inverse stress analysis using the focal mechanisms
AU: * Otsubo, M
EM: otsubo-m@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology (AIST), GSJ, 1-1-1, Higashi, Tsukuba, 305-8567, Japan
AU: Kubo, A
EM: akubo@cc.kochi-u.ac.jp
AF: Kochi earthquake observatory, 2-17-47 Asakura Honmachi, Kochi, 780-8073,
AB: We analyzed stress state in the connective region between Honshu and Ryukyu arc to discover the transitional stress between with and without backarc opening of the arcs around southwestern Japan. We used multiple inverse stress analysis method developed in structural geology. This technique can reduce artificial effect to make dataset for stress tensor inversion and provide opportunities to detect spatio-temporal heterogeneities of the stress field. We used focal mechanism solutions (best double couple components of regional moment tensors derived by Fnet, NIED, Japan) as input data of stress inversion. We analyzed three datasets which divided spatially along arc (from Ryukyu to Honshu). Because seismicity with moderate magnitude in forearc side is low, we obtained results only in the region of backarc side. Each result show strike-slip regime having two distinct clusters with different stress axes (30°). In perspective view, Shmax and Shmin directions rotate gradually from Ryukyu to Honshu. This result constrains pattern of the fan shaped stress trajectory between compressive Honshu arc and extensional Ryukyu arc, which is important issue to the understand geodynamics of subduction zone island arc. On the other hand to interpret multiple stress solutions and these stress ratio variations, locally heterogeneous stress state are required.
DE: 8123 Dynamics: seismotectonics
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: 2007 Fall Meeting