S-wave velocity structures of the Taipei Basin, Taiwan, using microtremor array measurements

•We study VS structures of the Taipei Basin using the array records of microtremors at 15 sites.•The alluvial thickness is ∼100–650 m and gradually increases from southeast to northwest.•Our results are in good agreement with well-logging data and seismic reflection studies.

The S-wave velocity structures of the Taipei Basin in Taiwan are investigated using the array records of microtremors at 15 sites. Dispersion curves at these sites are calculated using the frequency–wavenumber (F–K) spectrum method. The S-wave velocity structures in the Taipei Basin are then estimated by employing surface wave inversion technique. Harder strata sites have higher phase velocities than softer sites. If the S-wave velocity of the Tertiary Basement is assumed to be 1000 m/s, then the Quaternary alluvial thicknesses in the Taipei Basin are between about 100 m and 650 m. The thickness of the alluvium gradually increases from the southeast to the northwest. The inversion results are also in good agreement with well-logging data and seismic reflection studies of the Taipei Basin. The study concludes that microtremor array measurement is a useful tool for estimating S-wave velocity structure.