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Mapping Near-Surface Rigidity Structure using Co-located Pressure and Seismic Stations from the EarthScope Transportable Array

Jiong Wang, & Toshiro Tanimoto

Published August 15, 2019, SCEC Contribution #9860, 2019 SCEC Annual Meeting Poster #052

We propose a single-station approach to obtain shallow elastic structure by using co-located pressure and seismic instruments and apply this approach to stations in the EarthScope Transportable Array. This approach retrieves rigidity of the shallowest 50 or 100 m of the ground and provides complementary information to other techniques that examine near-surface S-wave velocity. Co-located data indicate that the coupling between atmosphere and solid Earth is strong for frequencies between 0.01 Hz and 0.05 Hz; and the coherence between pressure and seismic signals becomes low above 0.05 Hz, therefore our method focuses on the frequency range between 0.01 Hz and 0.05 Hz. This frequency range differs from that of most studies on wind-generated seismic noise, which usually focus on higher frequencies (> 1 Hz). Using this low frequency range and a homogeneous half-space model for the solid Earth, for which analytical solutions exist, we have estimated the near-surface rigidity structure at 784 TA stations. Different from our previous work in which we derived the rigidity from ratios between the vertical seismic power spectral density (PSD) and the co-located pressure PSD, this new approach uses the ratios between the horizontal PSD the co-located pressure PSD at each station. Our rigidity map shows a good spatial agreement with large-scale surface geological features, such as the Appalachian Mountains and the Mississippi Alluvial Plain. Even though the results correlate with various Vs30 models, there are stations show clear differences. Despite the fact that some variations may result from methodological differences, our approach can serve as an independent parameter to resolve potentially problematic locations in proxy-based models. Close Examination on those differences will lead to improvements of Vs30 models.

Wang, J., & Tanimoto, T. (2019, 08). Mapping Near-Surface Rigidity Structure using Co-located Pressure and Seismic Stations from the EarthScope Transportable Array. Poster Presentation at 2019 SCEC Annual Meeting.

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