Earth model space exploration in Southern California: Influence of topography, geotechnical layer, and attenuation on wavefield accuracy

Rasheed Ajala, Patricia Persaud, & Alan Juarez

Under Review July 25, 2022, SCEC Contribution #11904

Earth models play an important role in the geoscientific community for their use in deterministic earthquake hazard assessments, earthquake source research, and structural geologic studies. These models should represent the geology well while reasonably predicting important geophysical observations. We test two regional Southern California community models for their performance in earthquake hazard analysis. Our goal is to study the impact of certain geologic and model features on earthquake ground motion predictions. These Earth model add-ons include topography, geotechnical layering that reflects shallow weathered materials, and attenuation. Our results provide some counterexamples to factoids about their importance that are usually exaggerated in the literature without validation using actual data. We find that excluding topography in the elevation-reference model produced better waveform predictions. At the same time, including topography in the model developed without an elevation model had better waveform predictions, with the influence becoming less impactful at higher frequencies. Geotechnical layering had inconsistent marginal effects on the waveform predictions, improving them in some cases and deteriorating in others. Only attenuation performs as expected; it enhances wavefield predictions in all cases and becomes more critical at higher frequencies. Our results serve as caution and offer recommendations for developing and implementing Earth models.

Citation
Ajala, R., Persaud, P., & Juarez, A. (2022). Earth model space exploration in Southern California: Influence of topography, geotechnical layer, and attenuation on wavefield accuracy. Frontiers in Earth Science, (under review).