Japan Geoscience Union Meeting 2019

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[E] Poster

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

[S-CG48] Science of slow earthquakes: Toward unified understandings of whole earthquake process

Wed. May 29, 2019 10:45 AM - 12:15 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Satoshi Ide(Department of Earth an Planetary Science, University of Tokyo), Hitoshi Hirose(Research Center for Urban Safety and Security, Kobe University), Kohtaro Ujiie(Graduate School of Life and Environmental Sciences, University of Tsukuba), Takahiro Hatano(Earthquake Research Institute, University of Tokyo)

[SCG48-P37] Spatiotemporal distribution of regular and very low-frequency earthquakes in the northern part of the Ryukyu subduction zone

*Youichi Asano1, Kazuhiko Goto2, Hiroshi Yakiwara3, Shuichiro Hirano3 (1.National Research Institute for Earth Science and Disaster Resilience, 2.Association for the development of earthquake prediction, 3.Nansei-toko Observatory for Earthquakes and Volcanoes, Kagoshima University)

Keywords:very low-frequency earthquake, Ryukyu subduction zone

We have investigated detailed spatiotemporal distribution of regular and very low-frequency (VLF) earthquakes including an Mw 6.3 interplate event near Tanegashima along the Ryukyu trench on Jun. 08, 2019. This earthquake was followed four Mw4-5 class regular and many VLF earthquakes by the end of Jan., 2019. At first we estimated centroid moment tensors of these regular and several VLF earthquakes, respectively, from broadband seismograms recorded at the NIED F-net and temporally observation stations. In the next step, the known VLF earthquakes were selected to be template events for searching unknown VLF earthquakes from continuous seismograms. If there are several candidates of VLF earth quake, we select the most coherent event with a maximum cross-correlation coefficient averaged over all stations in every 180 seconds. Finally we estimated locations of the selected events from phase shift of the wavelets between the template and these selected events. Obtained result shows that activity of VLF earthquakes after the Mw 6.3 earthquake was started in the adjacent area east of this Mw 6.3 earthquake; however, the following Mw4-5 regular earthquakes occurred south of this area in the period of Jan. 25-30, 2019. In this period, the front of the VLF activity migrated toward east from these Mw4-5 events. Such a spatiotemporal distribution of regular and VLF earthquakes suggests that the after slip of the Mw 6.3 and/or an SSE caused these regular and VLF earthquakes.



Acknowledgment

This study is partly supported by JSPS KAKENHI Grant Number JP16H06473.