Japan Geoscience Union Meeting 2015

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Oral

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)

10:15 AM - 10:30 AM

[SCG57-15] Urgent seismic observation for the 2014 Northern-Nagano Prefecture Earthquake and complex fault system

*Shin'ichi SAKAI1, Eiji KURASHIMO1, Kazushige OBARA1, Takaya IWASAKI1, Hiroaki TAKAHASHI2, Satoshi MATSUMOTO3, Megumi KAMIZONO3, Tomomi OKADA4 (1.Earthquake Research Institute, the University of Tokyo, 2.Institute of Seismology and Volcanology, Graduate School of Science, Hokkaido University, 3.Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University, 4.Research Center for Prediction of Earthquakes and Volcanic Eruptions, Tohoku University)

Keywords:2014 Northern-Nagano Prefecture earthquake, urgent aftershock observation, precise aftershock distribution, multi-fault system

The 2014 Northern-Nagano Prefecture Earthquake (MJMA 6.7) occurred in central Japan at 22:08 on November 22, 2014 (JST). A temporal seismic network has deployed two days before the main shock, because an earthquake swarm occurred 4 days ago. Then the main shock occurred and the region of aftershocks spread, we installed jointly 13 new observation sites to determine the seismic activity. It was possible to decide the precise hypocenters because observational data located right above the main shock was used. Strong lateral heterogeneity in the velocity of the source area resulted in the locations of the epicenters determined in this study being located approximately 2.5 km east of those reported by the JMA routine catalogue. Using those high-resolution seismic data for early days, one major source fault and some minor faults were identified. The main shock located on the high angle distribution that eastern dipped. Much distribution is also existed, and those aren't always parallel with the inclination of the main shock.