Japan Geoscience Union Meeting 2015

Presentation information


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

[S-CG57] Structure, evolution and dynamics of mobile belts

Thu. May 28, 2015 9:00 AM - 10:45 AM IC (2F)

Convener:*Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Hiroshi Sato(Earthquake Prediction Research Center, Earthquake Research Institute, The University of Tokyo), Koichiro Obana(Research and Development Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology), Takuya NISHIMURA(Disaster Prevention Research Institute, Kyoto University), Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Aitaro Kato(Graduate School of Environmental Studies, Nagoya University), Jun Muto(Department of Earth Sciences, Tohoku University), Katsushi Sato(Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University), Shuichi Kodaira(Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and Technology), Takeshi Sagiya(Disaster Mitigation Research Center, Nagoya University), Tatsuya Ishiyama(Earthquake Research Institute, University of Tokyo), Makoto MATSUBARA(National Research Institute for Earth Science and Disaster Prevention), Yasutaka Ikeda(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Chair:Tadashi Yamasaki(National Institute of Advanced Industrial Science and Technology)

10:00 AM - 10:15 AM

[SCG57-14] Crustal deformation around the Kamishiro fault and its implications for the 2014 Northern Nagano earthquake

*Takeshi SAGIYA1, Naoko TERATANI1, Takuya NISHIMURA2, Hiroshi YARAI3, Hisashi SUITO3 (1.Nagoya University, 2.Kyoto University, 3.Geospatial Information Authority of Japan)

Keywords:Kamishiro Fault, 2014 Northern Nagano Earthquake, GPS, crustal deformation

The Itoigawa-Shizuoka Tectonic Line (ISTL) is a major geologic boundary intersecting the Japanese mainland into the northeastern and the southwestern parts. It is also an active fault system that is supposed to have a high seismic potential. We have conducted dense GPS observation and identified a highly localized E-W contraction
around the Kamishiro fault at the northern ISTL. Kinematic modeling of this deformation pattern suggests that the fault is dipping to the east and accommodating the E-W contraction by aseismic faulting below the depth of 2-4 km.

On November 22, 2014, a Mw 6.3 earthquake occurred at the Kamishiro fault. The hypocenter is located at a depth of 5 km and surface rupture appeared for about 9 km along the fault trace. Considering the pre-seismic deformation pattern and aseismic fault slip at depth, this earthquake is considered to rupture the remaining shallow locked part. Thus no further large earthquake is not anticipated in this area in the near future although much larger event is expected to occur along the whole ISTL.

This earthquake caused a heavy damage on a small neighborhood called Horinouchi. It should be noted that the same neighborhood had experienced a severe damage by another earthquake in 1714. Considering that the locked portion is limited to the shallowest 5 km and strain rate around this area is very large, it is possible that the same fault segment was reactivated in 300 years, which is an unusually short recurrence interval as a intra-plate active fault. This example demonstrates an importance of dense as well as precise geodetic observation for seismic hazard evaluation and understanding the crustal seismogenesis.