Update of the Lower Seismogenic Depth Model for Western U.S. Earthquakes

Yuehua Zeng, Mark D. Petersen, & Oliver S. Boyd

Submitted September 8, 2024, SCEC Contribution #13656, 2024 SCEC Annual Meeting Poster #230

We present an updated model of the lower seismogenic depth of earthquakes in the western United States (WUS), estimated using the hypocentral depths of events with magnitudes greater than 1, a crustal temperature model, and historical earthquake rupture depth models. The earthquake locations are sourced from the Advanced National Seismic System Comprehensive Earthquake Catalog (ComCat) spanning from 1980 to 2024. This data is supplemented with relocated seismicity in southern California (Hauksson et al., 2012) for higher precision and better resolution. We calculated the average depth of the deepest 10% of the events in the merged catalog using an adaptive radius (R) instead of a fixed 50 km. This initial R is determined based on the best depth location errors. Our findings show a strong correlation between this updated depth model and rupture depths derived from the coseismic slip of large earthquakes across the region. Generally, our estimated earthquake depths are deeper than the seismogenic depths previously determined for the Uniform California Earthquake Rupture Forecast version 3 (UCERF3) model, which was based on work by Petersen et al. (1996) using seismicity cross-sections along major fault zones in California. We also updated the brittle–ductile transition model using the WUS crustal temperature models by Blackwell et al. (2011) and Boyd (2020), applying it to the seismogenic depths in the model east of the Intermountain West Seismic Belt, where the seismicity rate is low. This updated depth model is valuable for recalibrating the lower geologic fault rupture depths and for constraining deformation and seismicity source models in updates to the U.S. Geological Survey National Seismic Hazard Model.

Key Words
Lower seismogenic depth

Citation
Zeng, Y., Petersen, M. D., & Boyd, O. S. (2024, 09). Update of the Lower Seismogenic Depth Model for Western U.S. Earthquakes. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Community Earth Models (CEM)