Abstract
AbstractShear-wave velocities (VS) have been widely used for the site characterization of earthquake ground motion. We report here our investigation of theS-wave velocity structures of Chia-Yi City, Taiwan using the array records of microtremors at seven sites. The dispersion curves at these sites were first calculated using the F-K method proposed by Capon (1969); theS-wave velocity structures in Chia-Yi City were then estimated by employing the surface wave inversion technique (Herrmann, 1991). At frequencies lower than about 1 Hz, the propagation directions are concentrated in the northwest and southwest quadrants. The generation of these may be attributed to the ocean waves of the Taiwan Strait. The harder site (CBA) has higher phase velocities, while the softer sites (CWB, SHP and YRU) have lower phase velocities, especially at frequencies between 1 and 5 Hz. The shallow velocity structures (0–1,500 m) can be roughly divided into four to five layers. The depth of the alluvium gradually increases from east to west and from north to south.
Highlights
For both theoretical simulations and ground motion predictions, it is essential to obtain concrete evidence pertaining to underground structures, especially for sedimentary layers overlying bedrock
We report here our investigation of the S-wave velocity structures of Chia-Yi City, Taiwan using the array records of microtremors at seven sites
The dispersion curves at these sites were first calculated using the F-K method proposed by Capon (1969); the S-wave velocity structures in Chia-Yi City were estimated by employing the surface wave inversion technique (Herrmann, 1991)
Summary
For both theoretical simulations and ground motion predictions, it is essential to obtain concrete evidence pertaining to underground structures, especially for sedimentary layers overlying bedrock. The Rayleigh-wave inversion technique using the array records of microtremors has been recognized as one of the most useful exploration methods to obtain the S-wave velocity structures of sedimentary layers in urbanized areas (Horike, 1985; Matsushima and Okada, 1990). In this method, longperiod microtremors are used to estimate deep S-wave velocity structures, while short-period microtremors (
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