Estimations of the S-wave velocity structures in Chia-Yi City, Taiwan, using the array records of microtremors

Abstract

Shear-wave velocities (V S ) have been widely used for the site characterization of earthquake ground motion. 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 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.

Estimation of shallow S-wave velocity structure in the Puli basin, Taiwan, using array measurements of microtremors

“…They correlated the frequency variation with the structure of the basin, investigated the directional properties of the noise wave eld and recognized the possible in uence of the basin structure on the propagation of seismic waves. Huang and Wu (2006) performed microtremor array measurements for a total of 28 arrays at seven sites to estimate the S-wave velocity structures in Chia-Yi City. According to the f -k analysis, at frequencies lower than about 1 Hz, the generation of microtremors may be attributed to the ocean waves of the Taiwan Strait.…”

The Wave Telescope Technique

“…The Capon method has been introduced in various geophysical multi‐point measurements such as experiments of ocean wave breaking (Babanin et al., 2011), tidal interval waves (Dushaw & Worcester, 1998), oceanic Rossby waves (Zang & Wunsch, 1999), atmospheric layer imaging (Chen et al., 2014), and seismic waves (Gal et al., 2016; Huang & Wu, 2006; Menon et al., 2014). The wave telescope technique has successfully been used to obtain the Cluster fluxgate magnetometer data to study the low‐frequency waves in near‐Earth space (e.g., foreshock, magnetosheath, and magnetotail) and turbulence in the solar wind.…”

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

“…The resulting model showed locally good agreement with the few existing data of velocity profiles. Huang and Wu (2006) estimated S-wave velocity structures (0-1500 m) in Chia-Yi City, Taiwan, using the array records of microtremors. Wu and Huang (2012) calculated the S-wave velocity structures (0-2000 m) of the Puli area, Taiwan and their results matched well the results from other seismic exploration methods.…”