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Group B, Poster #054, Seismology

Evaluating location and depth uncertainties in the Southern California earthquake catalog

Erika Jaski, Gabrielle Tepp, Ellen Yu, & Egill Hauksson
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Poster Presentation

2023 SCEC Annual Meeting, Poster #054, SCEC Contribution #13194 VIEW PDF
The Caltech/USGS Southern California Seismic Network (SCSN) has maintained a regional seismic event catalog since 1932. The physical network and analysis procedures have changed many times over the years, improving the quality and completeness of detected events. Currently, the SCSN operates an automated event detection system in real-time to detect events and provide initial information. The events are then manually reviewed by an analyst to improve the phase pick quality and, ultimately, the hypocenter and magnitude. Hypocenters are computed using hypoinverse with a single 1-D velocity model and station delays for all of Southern California and are accompanied by a few different parameters... that indicate how reliable the location and depth are. However, while horizontal and depth location errors computed by hypoinverse may provide a measure of precision, they don’t necessarily indicate how accurate the resulting depth or epicenter is. To better evaluate the quality of event hypocenters in the SCSN catalog, we can compare them to a relocated catalog produced using a 3-D velocity model and differential travel times that includes events since 1981. In this presentation, we explore the temporal and spatial trends in the typical hypocenter quality parameters and in the quality based on similarity to the relocated catalog. Better understanding of the hypocenter quality will allow us to more easily determine how best to adjust and update our network and analysis procedures to improve the accuracy of the SCSN event catalog. Both the SCSN and relocated catalogs are available for download here: https://scedc.caltech.edu/