Interpretation of stresses and subsurface structures in the case of Mt. Fuji area
IPGP - Îlot Cuvier
Séminaires de Sismologie
Kohtaro R. Araragi
ERI Univ Tokyo
Interaction of stresses in volcanic area has been discussed in previous study. In this research, we measure shear wave splitting on Mt. Fuji to understanding stresses in the area. After 2011 Tohoku-Oki Earthquake, Mw 5.9 earthquake occured on 15 March 2011 and numerious aftershocks are followed by the event. We used data from 2009 to 2012 at 24 seismic stations around Mt. Fuji. Measurement resutls show clear trends spatially in terms of fast polarization directions. The distribution of fast polarization directions near the summit show the radial pattern from the summit. By contrast, fast polarization directions at stations far from the summit have a trend in the NW-SE orientation that is pararell to the regional compression. Since the current measurement of shear wave splitting do not have adequate resolutionm we can not detect subtle temporal changes like in Brenguier et al. (2014). Interaction of gravity of volcanic edifice and regional stresses has been considered taking important role on geologic structures in Mt. Fuji area. We attmpted to verify this idea with stress modeling. The model indicates that the spatial distribution of maximum compression caused by the gravitational effect of volcanic edifice and regional stresses can show similar pattern with seismic anisotropy measured by shear wave splitting. In this presentation, I would also like to talk about my project with Florent Brenguier at ISTerre. In Brenguier et al. (2014), they discovered subtle velocity change beneath Quaternary period volcanoes in the eastern part of Japan. I would like to present ambient noise analysis focusing on the Mt. Fuji volcanic area.