Estimate of shear wave velocity, and its time-lapse change, from seismic data recorded at the SMNH01 station of KiK-net using seismic interferometry

Abstract

This study uses the deconvolution of small earthquakes registered in the SMNH01 station of KiK-net, one of the most important seismic networks which is located in Japan, to estimate effective shear wave velocities β, shear modulus μ, and quality factors Q, and to identify physical changes in the soil. This station has a borehole which is equipped with triaxial accelerometers installed at the surface and at 100m of depth. By deconvolving seismic events registered at surface and at 100m of depth, we obtain physical parameters. To interpret deconvolved waves, we use a one dimensional (1D) layered medium. Based on changes observed in amplitudes and arrival times of deconvolved waves, we identify time-lapse variations in shear wave velocities (maximum change in δβ/β=3.8%) and shear modulus (maximum change in δμ/μ=7.8%). The variations in shear wave velocities detected at station SMNH01 are mainly due to the combined influence of precipitation and recurrent seismic events.