Lower Seismogenic Depth Model of Western U.S. Earthquakes

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

Submitted September 11, 2022, SCEC Contribution #12553, 2022 SCEC Annual Meeting Poster #266

We present a model of the lower seismogenic depth of earthquakes in the western U.S. estimated using the hypocentral depths of events M>1 from the USGS National Earthquake Information Center (NEIC) catalog from 1980 to 2021 supplemented with seismicity in southern California that was relocated by Hauksson et al. (2012) to obtain higher precision and better resolution in the model. Previous determination of the seismogenic depth for the UCERF3 model was based on work by Petersen et al. (1996) who used seismicity cross sections along major fault zones in California. We calculated the average depth of the deepest 10% of the merged catalog using an adaptive radius of 50 km or more. Along the San Andreas Fault, the deepest seismogenic depths are located at 23 km around the Cholame segment, whereas the shallowest depths are located at about 10 km along the Rodgers Creek and Macaama faults. For the western U.S outside California, the depth varies between 10 and 25 km with an average around 14 km. We have also found very good agreement between the small magnitude depths and rupture depths derived from coseismic slip of large earthquakes across the region. This new seismogenic depth distribution correlates closely with the crustal temperature model derived from the heat flow distribution for the western U.S region (Blackwell et al., 2011). We developed a brittle-ductile transition model based on these temperature profiles, that we use to replace seismogenic depths in the model east of the Frontal Range and Intermountain West Seismic Belt where seismicity rate is low. This updated depth model could be used to recalibrate the lower geologic fault rupture depths in the western US and applied to the background seismicity source model in the 2023 update of the National Seismic Hazard Model (NSHM).

Key Words
Lower seismogenic depth

Zeng, Y., Petersen, M. D., & Boyd, O. S. (2022, 09). Lower Seismogenic Depth Model of Western U.S. Earthquakes. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
SCEC Community Models (CXM)