Invited Seminar by Kevin Chao on 2012/09/28


日時: 2012年9月28日(金) 15:00-16:30
場所: 理学部E館セミナー室101
主催: 名古屋大学大学院環境学研究科 地震火山研究センター
概要: 巨大地震によって励起された(地球表面を伝わる)「表面波」で誘発された微動とその地球科学的意義について、彼の博士論文研究を中心に講演して頂きました。





Title: Global Search of Deep Triggered Non-Volcanic Tremor
Dr. Kevin Chao (Earthquake Research Institute, University of Tokyo)

Abstract:

Deep“non-volcanic” tremor has been observed at many major plate-boundary faults. Recent studies have shown that triggered tremor occurs on the same fault patches as ambient tremor and can be used as a proxy to estimate background tremor activity. A systematic global search of triggered tremor could help to identify the physical mechanisms and necessary conditions for tremor generation. Following our previous studies, we conduct a global search for tremor triggered by teleseismic earthquakes on major subduction zones around the Pacific Rim. These include the main islands of Japan (i.e., Kyushu, Shikoku, Honshu, and Hokkaido), New Zealand, the Cascadia subduction zone, Alaska and Aleutian Arc, and the major subduction zones in Central and South America. In addition, we examine major strike-slip faults around the Caribbean plate, the Alpine fault in the South Island of New Zealand, the Queen Charlotte fault in northern Pacific Northwest Coast, and the San Andreas fault system in California, and the collision environment in Taiwan. In each place, we first identify triggered tremor as a high-frequency non-impulsive signal that is in phase with the large-amplitude teleseismic waves. When possible, we locate triggered tremor using a standard envelope cross-correlation technique. We also calculate the dynamic stress and check the triggering relationship with the Love and Rayleigh waves. Finally, we calculate the apparent tremor triggering potential with the local fault orientation and surface-wave incident angles. Our current results suggest that tremor could be triggered at many plate-boundary faults in different tectonic environments. Their triggering behavior could be best explained under the Coulomb-Griffith failure criteria. The apparent triggering threshold is on the order of 1-10 KPa, although this value could be partially influenced by the background noise level or quality and quantity of seismic data. Our next step is to correct the apparent tremor triggering potential in each region, then compare it with the tectonic age in different tectonic environment.


略歴等:

Dr. Tzu-Kai Kevin CHAO (趙子凱)
Home country: Republic of China, TAIWAN

Education
•2012.05 Ph.D. Geological Sciences in the school of Earth and Atmospheric Sciences, Georgia Institute of Technology, Georgia, USA (Advisor: Dr. Zhigang Peng)
•2009.05 M.S. in the school of Earth and Atmospheric Sciences, Georgia Institute of Technology, Georgia, USA
•2001.08 M.S. in Earth Sciences, National Taiwan Normal University(国立台湾師範大学), Taiwan
•1997.06 B.S. in Physics, Fu-Jen Catholic University(輔仁大学), Taiwan

Employment
•2012- Postdoctoral Fellow in the Earthquake Research Institute, the University of Tokyo, Japan (Host Professor: Dr. Kazushige Obara)
•2006-2012 Research & Teaching Assistant in the Georgia Institute of Technology, USA

Personal website: http://www.kevinchao.com/


紹介:

Dr. Kevin Chao got his PhD. at the Georgia Institute of Technology, Georgia, US, in May, 2012. He is one of pioneering researchers on non-volcanic tremor triggered by passage of teleseismic surface waves. Now he has stayed at the Earthquake Research Institute, the University of Tokyo, collaborated with Prof. Kazushige Obara.

Kevin Chaoさんはプレート収束境界における微動に関して先駆的研究をされている方の一人で、今年(2012年)5月にアメリカ合衆国ジョージア州アトランタにあるジョージア工科大学において博士号(PhD)を取得されました。現在は、東京大学地震研究所にポスドクとして滞在され、微動及び低周波地震の研究の第一人者である小原一成教授と研究を進めています。

地震火山研究センター研究員 永井 悟


感想:

今回はKevin Chao氏に遠地地震によって誘発された世界中の深部低周波微動について様々なお話をして頂きました。遠地地震の表面波(Rayleigh波やLove波)の振幅や到来方向,微動発生域の断層形状の違いなどから誘発の閾値を模索するといった興味深い研究でした。話を聞いていた学生も,Kevin Chao氏のお話の内容と興味の方向性が合えば,きっと研究のやる気をトリガーされたに違いないでしょう。発表者のKevin Chao氏に感謝致します。

D3 吉本 昌弘



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