Toward a Statewide Community Model for Stress Orientation and Stressing Rate

Karen Luttrell, Jeanne L. Hardebeck, & Elizabeth H. Hearn

Submitted September 8, 2024, SCEC Contribution #13675, 2024 SCEC Annual Meeting Poster #225

One of the key priorities for the Statewide California Earthquake Center is improving observations and closing critical data gaps for the suite of Community Earth Models (CEM). The Community Stress Model (CSM) was developed throughout SCEC4 and SCEC5 and includes a range of models of in situ stress orientation, stress accumulation rate, and some estimates of stress magnitude from across southern California. As we expand our investigations of earthquake system science to the full San Andreas Fault System (SAFS), it is vital that we develop statewide estimates of 3D stress that can support the broader investigations of the SCEC community. Here we provide updates on our ongoing work collecting existing models of stress orientation and strain rate, particularly throughout northern California, and synthesizing them into stress orientation and stressing rate models consistent with existing CSM contributions. Our newly defined common grid for CSM products extends from the current southern California grid definition, for full backward compatibility. To date, there have been no published stress inversion studies made for the entirety of central or northern California, perhaps because of the many regions of northern California with low seismicity rate and low station density. However, we have incorporated several published focal mechanism inversion models of stress orientation from regions of central and northern California, and compare their resulting patterns with one another and with prior results from southern California. We also calculate new statewide stressing rate estimates from existing western U.S. deformation rate models, including those used in the recent National Seismic Hazard Model update, using simple assumptions about the elastic moduli in the region. Many of these estimates do cover the entirety of the state of California, including all sections of the SAFS as well as secondary fault systems throughout the state. We again compare their resulting patterns with one another and with prior results from southern California. Our ultimate goal is to formally release these products and associated metadata in standardized CSM format both as part of the permanent CSM archive, and via the newly developed CSM visualization tool.

Key Words
CSM, stress, stressing rate

Citation
Luttrell, K., Hardebeck, J. L., & Hearn, E. H. (2024, 09). Toward a Statewide Community Model for Stress Orientation and Stressing Rate. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Community Earth Models (CEM)