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Earthquake Source Parameter Analysis Using Peak Narrow Band Displacement Amplitudes

Trey C. Knudson, William L. Ellsworth, & Gregory C. Beroza

Submitted September 10, 2023, SCEC Contribution #13037, 2023 SCEC Annual Meeting Poster #031

We present a source parameter analysis of over 3800 earthquakes in the 2019 Ridgecrest sequence as part of the SCEC Stress Drop Study. We determine the corner frequency and moment by measuring an apparent spectrum defined as the maximum amplitude of the S-wave displacement seismogram after it is passed through a series of bandpass filters. From each seismogram we extract 17 peak amplitude measurements in half-octave bands between 0.125 and 46 Hz. The apparent spectrum is defined by the half-octave peak amplitudes. We obtain the source spectrum by applying corrections for site and path effects using a frequency-dependent distance correction based on Richter's local magnitude relation (-log(A0)). Our frequency-dependent attenuation relations account for geometric spreading, attenuation, and local site amplification. We fit an omega-squared Brune model to the mean spectrum from all observing stations to obtain the moment and corner frequency for each event. Given an S-wave arrival for each event, this workflow is fully automated and reproducible. Through this approach we find that moment magnitude can be reliably measured using this method for earthquakes at least as small as Mw 1.8, and that the regional, frequency-dependent path and site corrections allow for a more robust estimate of source parameters.

Knudson, T. C., Ellsworth, W. L., & Beroza, G. C. (2023, 09). Earthquake Source Parameter Analysis Using Peak Narrow Band Displacement Amplitudes. Poster Presentation at 2023 SCEC Annual Meeting.

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