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Shear Wave Velocities in the Central Eastern United States

Mehrdad Hosseini, Paul G. Somerville, Andreas Skarlatoudis, Jeff R. Bayless, & Hong Kie Thio

Published July 27, 2016, SCEC Contribution #6379, 2016 SCEC Annual Meeting Poster #170

USARRAY and ANSS seismic stations provide an invaluable waveform dataset for studying ground motion attenuation in the Central and Eastern United States. However, the dataset is useful only after the site effects at each station are well understood. Since there are many stations in USARRAY and ANSS, it would be costly to accurately determine sub-surface velocity structure beneath every station using geophysical exploration techniques involving arrays, such as ReMi and SASW. It would be more economical to estimate the site effects with waveforms recorded at the seismic stations. Such approaches have been widely applied, but most of them involve the frequency dependent ratio between the horizontal and vertical component of either ambient noise or S waves from earthquakes. The horizontal component of P waves can also be used to infer sub-surface velocity structure. It is demonstrated that the ratio of radial to vertical P waves is mostly sensitive to sub-surface shear velocity, so the radial/vertical ratio of the P wave is a good indicator of subsurface shear velocity. Therefore, the subsurface velocity structure can be estimated using an approach similar to teleseismic P receiver functions, but at much smaller scale and higher frequency that matches well with results from ReMi and Refraction/Reflection techniques (Ni et al. 2014). We used the approach introduced by Ni et al. (2014) and calibrated our models with findings from Ni and Somerville (2013) to obtain data on shallow shear-wave structure in the Central and Eastern United States. A rich database of local earthquakes from 2009 to 2013 recorded at ~560 seismic stations was analyzed and associated receiver functions were inverted. The results are in reasonable agreement with local geology and with the results of Ni and Somerville (2013), Ni et al. (2014) and Kim et al. (2014). The data are made publically available for future refinement.

Hosseini, M., Somerville, P. G., Skarlatoudis, A., Bayless, J. R., & Thio, H. (2016, 07). Shear Wave Velocities in the Central Eastern United States. Poster Presentation at 2016 SCEC Annual Meeting.

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