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| | Abstract | | In order to estimate two-dimensional shallow S-wave velocity structures, we tried chain array analysis and seismic interferometry analysis on observed microtremors record. We observed microtremors for 2 days in Inzai City, Chiba Prefecture. We set geophones on both road shoulders with a distance of the survey line shifted 3.5 m. Furthermore, we set geophone in a straight line at intervals of about 12 m on the road. In the chain-array analysis, we obtained 2-D S-wave velocities of about 70 to 100 m/s at a depth of about 10 to 20m, which were varying laterally. Also, it was found that S-wave velocities below the central area of the survey line were about 200 m/s at the depth of 30 m, but S-wave velocities below both ends of the survey line were about 150m/s. The one-dimensional S-wave velocity structure obtained from microtremors survey by using an array with a radius of up to about 140m array spacing agreed with the result by Kawasaki et al. (2006). In the seismic-interferometry analysis, we could see two characteristic phases propagating at the velocities of about 1500m/sec and 350m/sec on the cross-correlation function records. |
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