Permalink : http://hdl.handle.net/2115/44471

JaLCDOI : 10.14943/gbhu.73.159

S-wave velocity structures were explored in the northwestern part of Ishikari plain from microtremor array measurements. We measured microtremors using seismometer arrays at 3 sites on 4 days during May - July 2005. Phase velocities in a frequency range of 0.22 - 4.32 Hz were estimated using SPAC（SPatial AutoCorrelation）analysis of the microtremor records. The S-wave velocity structures were obtained by the inversion from the phase velocities using a genetic algorithm technique. The inverted S-wave velocity structures obtained from the microtremor array surveys in the present and previous studies indicate that the S-wave velocities of a geologic layer clearly depend on the depth.