EGU2020-15135, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-15135
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Temporal Variations of Near-surface seismic structure of Taiwan revealed by coda interferometry

Sheng-Jyun Cai1, Li-Wei Chen2, Hsin-Yu Lee3, Ying-Nien Chen4, and Yuan-Cheng Gung1
Sheng-Jyun Cai et al.
  • 1Department of Geosciences, National Taiwan University, Taipei City, Taiwan (yrt12378@gmail.com)
  • 2Department of Earth and Planetary Science, University of California at Berkeley, CA, USA
  • 3Department of Earth and Planetary Sciences, University of California at Riverside, CA , USA
  • 4Department of Earth and Environmental Sciences, National Chung Cheng University, Chiayi, Taiwan

We report the temporal change of the near-surface(<400m) seismic structure of Taiwan revealed by coda interferometry. Following our earlier work (Chen et al., 2017), the Empirical Green’s Functions (EGF) of shear waves extracted from the earthquake coda recorded by the vertical pairs of borehole array, deployed by the Central Weather Bureau, are used to examine the temporal variations of vs and Vs azimuthal anisotropy at the borehole sites. In total, about 700 local events, from 2013 to 2018, are used in this study. The band-passed (3 – 8 hz) EGF extracted from each single event are stacked over variable time period to ensure the reliability of measurements and the desired temporal resolution. The averaged Vs and patterns of Vs azimuthal anisotropy are in good agreement with the site geology, the ambient stress and those reported in our early work. Apparent drop in the Vs isotropic velocities and perturbations in Vs azimuthal anisotropy are observed in few representative borehole sites, and we also noticed that such variations are tightly correlated with the occurrence of major earthquakes in Taiwan. We present the preliminary results and discuss the triggering mechanisms, the healing revolution, and their relationship with the site geology.

How to cite: Cai, S.-J., Chen, L.-W., Lee, H.-Y., Chen, Y.-N., and Gung, Y.-C.: Temporal Variations of Near-surface seismic structure of Taiwan revealed by coda interferometry, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15135, https://doi.org/10.5194/egusphere-egu2020-15135, 2020

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