Evaluating seismic velocity models in the Salton Trough, Southern California using spectral-element wave simulation of validation events

Rasheed Ajala, Patricia Persaud, Alan Juarez, & Gboyega Ayeni

Submitted August 14, 2019, SCEC Contribution #9577, 2019 SCEC Annual Meeting Poster #055 (PDF)

Poster Image: 
The Southern California ShakeOut Scenario considers a potential M7.8 earthquake that initiates on the southernmost section of the San Andreas fault in the Salton Trough, with energy propagating northward into the Los Angeles basin. To improve earthquake hazard assessments in the region, we must accurately forecast strong ground motions through realistic 3D earth models. Recently, we have utilized active-source data from reflection and refraction seismic experiments in the Salton Trough such as the 2011 Salton Seismic Imaging Project to produce 3D travel time velocity models for Coachella and Imperial Valley basins (Ajala et al., 2019; Persaud et al., 2016). Comparisons of our models with two popular community velocity models in Southern California – CVM-S4.26 and CVM-H15.1 – reveal significant differences in basin geometry and crustal heterogeneity. To investigate the accuracy of the models in ground motion prediction, we registered our velocity models into the SCEC Unified Community Velocity Model software framework. This facilitates the construction of hybrid velocity models and mesh generation.

For our validation tests, we plan to simulate medium-sized earthquakes with magnitudes between 3.5 and 5.5 in four velocity models with geotechnical layers in the top 350 m: (1) our travel time velocity models embedded in CVM-H15.1, (2) our travel time velocity models embedded in CVM-S4.26, (3) CVM-H15.1 only, and (4) CVM-S4.26 only. Simulations will be done using the SPECFEM3D Cartesian package, which implements the spectral-element solution to the 3D wave equation for hexahedral meshes. Discrepancies between observed and synthetic seismograms will provide information that can be used to improve scenario earthquake simulations used for future earthquake preparations in Southern California.

Citation
Ajala, R., Persaud, P., Juarez, A., & Ayeni, G. (2019, 08). Evaluating seismic velocity models in the Salton Trough, Southern California using spectral-element wave simulation of validation events. Poster Presentation at 2019 SCEC Annual Meeting.


Related Projects & Working Groups
Seismology