Rapid estimation of the moment magnitude of the 2011 Tohoku-Oki earthquake (Mw 9.0) from static strain changes

Abstract The 2011 Tohoku-Oki earthquake, of moment magnitude (M w) 9.0, occurred on March 11, 2011, on the boundary between the Pacific and North America tectonic plates. The preliminary report of the magnitude announced by the Japan Meteorological Agency just after the earthquake was 7.9, which was considerably smaller than the final calculated Mw of 9.0. I used data from nine borehole strainmeters deployed by the National Institute of Advanced Industrial Science and Technology to estimate a fault model with M w of 8.7 for the 2011 earthquake. This model was estimated using data recorded during the first 7 min after the origin time of the earthquake (5 min after the first P-wave arrival). To date, strainmeter data have rarely been used to derive earthquake fault models because observed strainmeter data often include noise caused by the local effect of earthquake shaking. My results indicate that strainmeter data can measure large changes of static strain that can be used to rapidly and precisely estimate earthquake fault models and moment magnitudes for great earthquakes and can provide an important and useful complement to analyses based on seismic waves

カツダンソウ ニ オケル ジシン カツドウド ノ テイリョウテキ ヒョウカ シュホウ ノ カイハツ ト ジシン カツドウ サイクル

京都大学0048新制・課程博士博士(理学)甲第11318号理博第2876号新制||理||1430(附属図書館)22961UT51-2005-D69京都大学大学院理学研究科地球惑星科学専攻(主査)助教授 渡辺 邦彦, 教授 竹本 修三, 教授 Mori James Jiro学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDA

自治体の防災に貢献する地震情報の構築と提供―GISによるデータベースの構築―

自治体や住民に貢献する地震情報の構築とその伝達手法の開発を目的とする．そのためには，まず基礎となるデータベースの構築が必要となる．本報告は，鳥取県を対象とした地震防災に関する情報のデータベース化についての報告である．データベース化にはGISを利用した．基本的な地図情報，地震防災に関連する震源，地盤構造，地下水観測情報についての説明，地震発生の特徴について震源，地盤情報を用いた解析例を示す．Working with Tottori prefecture as a target area, we prepared a basic database ofinformation for earthquake disaster prevention. Using GIS software, we created adatabase of information for earthquake disaster prevention, which includes hypocenterand seismic wave data, geological data, geophysical exploration data, and hotspring andgroundwater data. We analyzed these data and tried to estimate several features of thetarget area to help reduce earthquake damage.自治体や住民に貢献する地震情報の構築とその伝達手法の開発を目的とする．そのためには，まず基礎となるデータベースの構築が必要となる．本報告は，鳥取県を対象とした地震防災に関する情報のデータベース化についての報告である．データベース化にはGISを利用した．基本的な地図情報，地震防災に関連する震源，地盤構造，地下水観測情報についての説明，地震発生の特徴について震源，地盤情報を用いた解析例を示す．Working with Tottori prefecture as a target area, we prepared a basic database ofinformation for earthquake disaster prevention. Using GIS software, we created adatabase of information for earthquake disaster prevention, which includes hypocenterand seismic wave data, geological data, geophysical exploration data, and hotspring andgroundwater data. We analyzed these data and tried to estimate several features of thetarget area to help reduce earthquake damage

Temporary slip speed increases during short-term slow slip events with durations of one to three hours

Abstract Temporary slip speed increases with durations of 1–3 h were identified during short-term slow slip events in records of borehole and laser strainmeters in the Tokai region, Japan. They were found by searching for peaks of correlation coefficients between stacked strain data and ramp functions with rise times of 1 and 2 h. Although many of the strain steps were considered due to noise, some strain steps occurred with simultaneous activation of the deep tectonic tremors and shared source areas with the tremors. From 2016 to 2022, we observed five strain steps with simultaneous activation of tectonic tremors and coincidence of source locations with the tremors. Those strain steps occurred during short-term slow slip events and were temporary slip speed increases of the slow slip events. Those strain steps seemed to be related to successive occurrences with source migration of short-term slow slip events. The detrended strain steps corresponded to plate boundary slip events of moment magnitude around 5, which was consistent with the scaling law of slow earthquakes. Graphical Abstrac