5:30 PM - 5:33 PM
[SCG62-P01] Detection of seismic anisotropy from low frequency earthquake
3-min talk in an oral session
Keywords:low frequency earthquake, seismic anisotropy, fluid
In this study, we detected seismic anisotropy at the plate interface of the PHS slab from the isolated phase during non-volcanic tremor episode, which are categorized as low frequency earthquakes by the JMA (Nishide et al., 2000). The phases are regarded as S-wave and used by hypocenter determination. Therefore, in order to detect anisotropy, we utilized S-wave splitting method (e.g., Ando et al., 1983), in which seismic anisotropy is represented by polarization direction of fast S-wave (direction of anisotropy) and delay time between two S-waves.
Preliminary result of S-wave splitting analyses showed that the directions of anisotropy are tend to be orientated in the East-West trending direction and the delay times are 0.2-0.4 sec. In general, however, anisotropy obtained by S-wave splitting analysis is strongly affected by anisotropy near the receiver. In fact, the obtained anisotropy in this study is consistent with crust anisotropy in the study area. In order to rigorously discuss anisotropy around the source region, we have to remove the effect of the anisotropy in the crust.