S41B-2746
Monitoring of Seismic Anisotropy at the Time of the 2008 Iwate-Miyagi Earthquake.
Thursday, 17 December 2015
Poster Hall (Moscone South)
Maria Saade1, Jean-Paul Montagner1, Philippe Roux2, Katsuhiko Shiomi3, Bogdan Enescu4 and Qingyu Wang2, (1)Institut de Physique du Globe de Paris, Paris, France, (2)Université Joseph Fourier, Grenoble, France, (3)NIED National Research Institute for Earth Science and Disaster Prevention, Tsukuba, Japan, (4)University of Tsukuba, Tsukuba, Japan
Abstract:
We investigate temporal variations of polarization of surface waves at the time of the June 13, 2008 Iwate-Miyagi Nairiku earthquake (Mw = 6.9) using passive image interferometry. We use continuous data recorded at 20 high-sensitivity seismic stations (Hi-net) from mid-2007 till end 2009. We compute cross-correlations of ambient seismic noise between each pair of 3-component stations, at the frequency of 0.08-0.22 Hz. The temporal variations of surface waves polarization (Ψ) show slow and weak variations due to seasonal changes superposed to rapid and strong variations at the time of the earthquake and slightly before, at the end of april. Strong change in Ψ (of the order of 10°) might be related to change in the orientation of cracks distribution, hence change in the induced extrinsic anisotropy between two receivers.
