Japan Geoscience Union Meeting 2014

Presentation information

Oral

Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG66_30AM1] Toward the integrated understanding of crustal deformation in plate convergence zones

Wed. Apr 30, 2014 9:00 AM - 10:45 AM 414 (4F)

Convener:*Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Yuji Yagi(Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba), Takeshi Sagiya(Disaster Mitigation Research Center, Nagoya University), Manabu Hashimoto(Disaster Prevention Research Institute, Kyoto University), Masanobu Shishikura(Active Fault and Earthquake Research Center, GSJ/AIST), Shoichi Yoshioka(Research Center for Urban Safety and Security, Kobe University), Yasutaka Ikeda(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Gaku Kimura(Department of Earth and Planetary Science of the Graduate School of Science, The University of Tokyo), Mitsuhiro Matsu'ura(The Institute of Statistical Mathematics), Chair:Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Saeko Kita(National Research Institute for Earth Science and Disaster Prevention)

9:30 AM - 9:45 AM

[SCG66-03] Crustal deformation in the Mid-Niigata area and its implication for strain concentration

*Takeshi SAGIYA1, Angela MENESES1 (1.Nagoya University)

Keywords:Strain concentration, Niigata-Kobe Tectonic Zone, 2004 Chuetsu earthquake, 2007 Chuetsu-oki earthquake, aseismic faulting, inelastic deformation

The Mid-Niigata area is located within the concentrated strain belt along the eastern margin of the Japan Sea. This area suffered from two large earthquakes, the 2004 Chuetsu and the 2007 Chuetsu-oki earthquakes. Based on GPS velocity data calculated from daily coordinate time series of GEONET, we identified significant time dependence of the interseismic crustal deformation patterns before, between, and after these two earthquakes. Modeling results of the deformation pattern changes are summarized as follows. 1) Contraction before 2004 occurred between the source regions of the two earthquakes and it was attributed to aseismic faulting across almost the whole elastic layer, implying that the observed strain was largely inelastic. This interpretation is also supported from a fact that the historical seismic energy release in this area is much smaller than that expected from geodetic strain accumulation. 2) After two earthquakes, aseismic faulting seems to have continued without explicit time decay. The aseismic faulting is estimated close the source fault of the main shocks, implying that postseismic strength recovery did not occur on the main shock fault or a nearby parallel fault was activated to accommodate regional contraction. This is consistent with an idea that the upper crust in this area is segmented to smaller blocks and the mechanical behavior is very sensitive to external stress changes.