Effect of Time Window and Spectral Measurement Options on Empirical Green's Function analysis using DAS Array and Seismic Stations

Xiaowei Chen, Jiuxun Yin, Colin N. Pennington, Qimin Wu, & Zhongwen Zhan

Accepted February 4, 2025, SCEC Contribution #14152

The recorded seismic waveform is a convolution of event source term, path term and station terms. Removing high-frequency attenuation due to path effect is a challenging problem. Empirical Green's Function (EGF) method uses nearly collocated small earthquakes to correct the path and station terms for larger events recorded at the same station. However, this method is subject to variability due to many factors. We focus on three events that are well recorded by the seismic network and a rapid response DAS (distributed acoustic sensing) array. Using a suite of high-quality EGF events, we assess the influence of time window, spectral measurement options and types of data on the spectral ratio and relative source time function (RSTF) results. Increased number of tapers (from 2 to 16) tends to increase the measured corner frequency and reduce the source complexity. Extended long time window (e.g., 30s) tends to produce larger variability of corner frequency. The multi-taper algorithm that simultaneously optimizing both target and EGF spectra produces the most stable corner frequency measurements. The stacked spectral ratio and RSTF from the DAS array are more stable than two nearly seismic stations, and are comparable to stacked results from the seismic network, suggesting that DAS array has strong potential in source characterization.

Citation
Chen, X., Yin, J., Pennington, C. N., Wu, Q., & Zhan, Z. (2025). Effect of Time Window and Spectral Measurement Options on Empirical Green's Function analysis using DAS Array and Seismic Stations. Bulletin of the Seismological Society of America, (accepted).