IAG-IASPEI 2017

講演情報

Oral

IASPEI Symposia » S09. Open session: Earthquake generation process - physics, modeling and monitoring for forecast

[S09-2] Open session: Earthquake generation process – physics, modeling and monitoring for forecast II

2017年8月1日(火) 10:30 〜 12:00 Room 503 (Kobe International Conference Center 5F, Room 503)

Chairs: Alexey Zavyalov (Institute of Physics of the Earth RAS) , Naoshi Hirata (ERI)

11:15 〜 11:30

[S09-2-04] Testing the Coulomb stress triggering hypothesis for three recent megathrust earthquakes

Takeo Ishibe1, Yosihiko Ogata2, 3, Hiroshi Tsuruoka2, Kenji Satake2 (1.Association for the Development of Earthquake Prediction, Tokyo, Japan, 2.Earthquake Research Institute, the University of Tokyo, Tokyo, Japan, 3.The Institute of Statistical Mathematics, Tokyo, Japan)

We test the static Coulomb stress triggering hypothesis for three recent megathrust earthquakes (the 2004 Sumatra-Andaman earthquake, the 2010 Maule earthquake, and the 2011 Tohoku-Oki earthquake) using focal mechanism solutions for actual earthquakes as receiver faults to calculate Coulomb stress changes. For the 2004 Sumatra-Andaman and 2011 Tohoku-Oki earthquakes, the median values of the Coulomb stress changes for 100 consecutive earthquakes revealed temporal changes from approximately zero before the megathrust earthquake to significant positive values following the mainshock, followed by a decay over time. Furthermore, the ratio of the number of positively to negatively stressed receiver faults increased after the megathrust. These results support the triggering hypothesis that the static stress changes imparted by megathrust earthquakes cause seismicity changes. This is in contrast to the results of a previous study that used optimally orientated receiver faults to calculate Coulomb stress changes, and this difference indicates the importance of considering the spatial and temporal heterogeneities of receiver fault distributions. For the 2010 Maule earthquake, however, the results are strongly dependent on fault-slip models. Since most receiver faults are concentrated in the mainshock source region, slip models significantly affect the computed Coulomb stress changes and sometimes cause anomalous stress concentrations along the edge of each sub-fault.