[S-SS29_28PM2] Earthquake Source Processes and Physics of Earthquakes

[SSS29-P08_PG] Focal mechanisms of the triggered tremor beaneath the Hinagu fault zone, southwestern part of Japan

3-min talk in an oral session

*Masahiro MIYAZAKI¹, Satoshi MATSUMOTO², Hiroshi SHIMIZU² (1.Grad. Sch. Sci., Kyushu Univ., 2.SEVO, Kyushu Univ.)

Keywords:triggered tremor, focal mechanisms, Hinagu fault zone

Non-volcanic tremors induced by large amplitude surface wave have been detected all over the world. Most of them are located on and near the plate boundary (Miyazawa and Mori, 2005; Nadeau and Dolene, 2005) and few of them are near volcanoes (Obara, 2012). Chao and Obara (2012, SSJ) found the triggered tremor that located beneath the Hinagu active fault zone, western part of Kyushu Island, Japan. Miyazaki et al. (2013, SSJ) reported that the tremor occurred beneath the seismogenic zone.In this study, we attempted to estimate focal mechanisms of the tremors triggered by the surface wave of the 2012 Sumatra earthquake. We use the method developed by Hirasawa (1966) that uses the S wave polarization angles. We eliminated the data with low Signal-to-Noise ratio because the angles of waves of tremors were sensitive to background noise.As a result, we found that focal mechanisms of the triggered tremors were roughly consistent with regional stress field. They could provide constraint for investigating dynamic triggering process of the tremor.AcknowledgementWe used the seismic data from Kyushu University, the Japan Meteorological Agency, the National Research Institute for Earth Science and Disaster Prevention and Kagoshima University.