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Seismic source and path parameters in Central California estimated with recorded ground motion

Jorge G. Crempien, & Ralph J. Archuleta

Published August 15, 2017, SCEC Contribution #7774, 2017 SCEC Annual Meeting Poster #020

With strong motion networks deployed in Central California, we used recorded shear-waves generated by earthquakes to estimate shear-wave quality factor and kappa in this region. For this we used both a parametric and non-parametric approach, with 23 earthquakes with magnitudes ranging between Mw 3.5-6.0, recorded at 32 different seismic stations. For this, we computed the Morlet continuous wavelet transform (CWT) for each horizontal acceleration recording. We then proceeded to integrate the CWT along the time domain between the onset of the S-wave and the end of this phase. This was done to estimate the Fourier amplitude spectrum of acceleration. The advantage of first computing the Morlet CWT and integrating along the time domain is to naturally smooth the Fourier spectrum between frequencies. We find a dependence of shear-wave quality factor with frequency, and our average kappa estimate for this region is ~35 ms.

We also analyzed the coda portion of seismograms to estimate coda intrinsic quality factor. The envelopes of coda were computed for different Butterworth bandpass filtered data to estimate the energy density in time. We then fitted the theoretical energy flux to the data with the method of Frankel and Wennerberg (1987). Preliminary results show intrinsic quality factor values of ~315, 720, 890 and 1100 at 1-2, 2-4, 4-8, and 8-16 Hz frequency bands. The coda scattering estimates are ~1000.

Key Words
seismic quality factor; kappa; Central California

Crempien, J. G., & Archuleta, R. J. (2017, 08). Seismic source and path parameters in Central California estimated with recorded ground motion. Poster Presentation at 2017 SCEC Annual Meeting.

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