Three-component microtremor measurements and microtremor array measurements have been performed at 6 points in central Mexico City. The microtremor array measurements used 25 to 650 m triangular arrays and clear dispersion curves were obtained between 0.3 and 10 Hz. The peak frequencies of the Horizontal and Vertical ratio (H/V) of spectra vary from 0.25 to 2 Hz. A joint inversion of an H/V spectrum and a dispersion curve is applied to observed data and S-wave velocity models down to a depth of 200 m were obtained. A low velocity layer with S-wave velocity lower than 150 m/s existed at a depth of 70 m at the middle of the Mexico basin. It seems that the peak frequency of 0.25 Hz in the H/V spectra is due to this shallow low velocity layer.
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