Japan Geoscience Union Meeting 2018

Presentation information

[EJ] Evening Poster

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

[S-CG57] Dynamics in mobile belts

Wed. May 23, 2018 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Hikaru Iwamori(海洋研究開発機構・地球内部物質循環研究分野)

[SCG57-P17] Coulomb stress change on the fault in Japan assumed from focal mechanism estimated from GNSS surface displacements of GEONET

*Masayuki Yamanaka1, Satoshi Fujiwara1, Hiroshi Yarai1, Takuya NISHIMURA2 (1.Geospatial Information Authority of Japan, 2.Disaster Prevention Research Institute Kyoto University)

Keywords:Coulomb stress change (ΔCFS), GNSS


Many studies used Coulomb stress change (ΔCFS) to discuss effects of large tectonic events like large earthquakes on surrounding faults. Calculation of ΔCFS is usually applied dislocation model assuming in an elastic half-space. It requires a source fault model for each tectonic event. On the other hand, previous studies (Ueda & Takahashi 2005; Ohzono & Takahashi 2016) suggest a method to calculate ΔCFS directly from the observed GNSS displacement. If the method reasonably works, it gives ΔCFS imparted by not only large tectonic events but also constant deformation. Nishimura (2017) examined efficacy of the method, and demonstrated ΔCFS increase on some fault segment ruptured by large earthquake before their rupture.

The purpose of this study is to demonstrate that actual earthquakes are consistent with ΔCFS calculated by the constant deformation from the observed GNSS displacement.

Method and Result

We calculate ΔCFS in same way to Nishimura (2017) on all source faults before the 2011 Tohoku-oki Earthquake imparted by the constant deformation observed by a GNSS. When the depth of hypocenter is less than 20km, approximately 70 % of calculated ΔCFS is positive, and annually increases several kPa (fig. 1, 2). The result is as our expectation that the method to calculate ΔCFS directly from the observed GNSS displacement reasonably works at a shallow depth in the upper crust.