A study on stress sensitivity of seismic velocity at shallow media using the earth tide and seismic wave interferometry

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We used the tidal effect acting on the solid earth by the moon to examine the strain sensitivity of seismic velocity at shallow structure. We retrieved seismic waves propagating between two sites by cross-correlating the ambient noises for the dilatational and contractional episodes of the earth tide, respectively. Travel time differences of the seismic waves for the two episodes are measured for the ambient noises recorded at a small seismic array deployed on the foot of Mt. Iwate and Hi-net data. The results show that the seismic velocity at the dilatational episode is slightly lower than that at the contractional one. The strain sensitivity is estimated to be about 2-7x10^4 /strain.