HR: 16:00h
AN: S34C-01    [Abstracts]
TI: Tectonic loading of active faults in central Japan revealed by dense GPS observations
AU: * Sagiya, T
EM: sagiya@seis.nagoya-u.ac.jp
AF: Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
AU: Ohzono, M
EM: makozono@gmail.com
AF: Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
AU: Hirahara, K
EM: hirahara@kugi.kyoto-u.ac.jp
AF: Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
AU: Hashimoto, M
EM: hasimoto@rcep.dpri.kyoto-u.ac.jp
AF: DPRI, Kyoto University, Gokasho, Uji, 611-0011, Japan
AU: Hoso, Y
EM: hoso@rcep.dpri.kyoto-u.ac.jp
AF: DPRI, Kyoto University, Gokasho, Uji, 611-0011, Japan
AU: Wada, Y
EM: yasuo@rcep.dpri.kyoto-u.ac.jp
AF: DPRI, Kyoto University, Gokasho, Uji, 611-0011, Japan
AU: Takeuchi, A
EM: takeuchi@sci.u-toyama.ac.jp
AF: Toyama University, Gofuku-cho, Toyama, 930-8555, Japan
AU: Douke, R
EM: d0671304@ems.u-toyama.ac.jp
AF: Toyama University, Gofuku-cho, Toyama, 930-8555, Japan
AU: Nishimura, T
EM: t_nisimura@gsi.go.jp
AF: Geographical Survey Institute, Kitasato 1, Tsukuba, 305-0811, Japan
AU: Yarai, H
EM: yarai@gsi.go.jp
AF: Geographical Survey Institute, Kitasato 1, Tsukuba, 305-0811, Japan
AB: We have been conducting dense GPS observations around two active faults zones in central Japan, the Atotsugawa fault (AF) system and the Itoigawa-Shizuoka Tectonic Line (ISTL) fault system. These faults constitute a part of the Niigata-Kobe Tectonic Zone, the inland strain concentration zone detected by the nationwide continuous GPS network. Our dense observations provide a key to understand detailed deformation pattern within the deformation zone and to solve the physical mechanism of the tectonic loading of active faults. AF fault sustem is a group of ENE-WSW trending right-lateral strike slip faults. Among three major faults in the fault system, AF is considered to play an important role and have the largest slip deficit of 3-5mm/year, which is consistent with the geologic slip rate. GPS observation indicates that the oblique contraction across AF may be partitioned into fault-normal and fault-parallel components, which are accommodated differently. Contraction across the fault distributes more widely. ISTL fault system is a major geologic structure in central Japan. The fault has a high probability of a large event. We have conducted a campaign GPS observation at 28 sites around ISTL every year since 2002. The campaign observation results revealed laterally heterogeneous deformation along the fault. In the northern part, WNW-ESE contraction is dominant, consistent with a reverse faulting of this portion. Concentrated contraction near the fault suggest that the stress is not accumulated but released. On the other hand, the Gofukuji fault in the central ISTL is characterized by left-lateral shear, implying strike slip faulting. The left-lateral shear strain is widely distributed over a long distance. Such a distributed shear strain implies stress relaxation in the lower crust and the fault may be in the latest stage of its interseismic period.
DE: 1209 Tectonic deformation (6924)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1243 Space geodetic surveys
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8159 Rheology: crust and lithosphere (8031)
SC: Seismology [S]
MN: 2007 Fall Meeting