← Back to Sessions

Evaluation of Seismic Community Velocity Models With Simulations of Small Earthquakes

Description: 

Seismic community velocity models (CVMs) are foundational for many basic and applied topics ranging from derivations of earthquake source properties to simulations of ground motions. CVM accuracy directly impacts the epistemic uncertainty of synthetic wave fields generated by earthquakes or 3D physics-based simulations. We present an innovative methodology to evaluate the epistemic uncertainty reflected in key intensity measures of ground motions related to seismic hazard analysis. This methodology involves simulating point source approximation wavefields from small historic earthquakes located in different parts of the crustal volume of interest and comparisons of results to observations. Using small events and the point source approximation facilitates a focus on properties of the CVM rather than finite source ruptures. Evaluation of differences between observed and synthetic data in spectral amplitude, phase matching, and signal duration allows us to estimate epistemic uncertainties and identify features and subregions of the CVM to improve. Here, we apply this framework to evaluate the performance of CVMs developed for southern and northern California. The evaluation employs three-dimensional physics-based ground motion simulations of sets of local small earthquakes with magnitudes ranging from 3.5 to 4.5. Because of the relatively low ground-motion amplitude induced by these earthquakes, the soil response is expected to be well-represented as linear at all recording sites. Therefore, the misfit between observed and synthetic waveforms can be mainly attributed to structural complexities not fully represented in the examined CVMs and, to a lesser extent, the source parameterization (location, depth, focal mechanism, source time function). Maps displaying the spatial distribution of residuals in the spectral domain facilitate the recognition of areas where each model performs better than the others and provide important guidance for future refinements of the CVMs.

Session: Physics-Based Ground Motion Modeling - I

Type: Oral

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Camilo Ignacio

Student Presenter: No

Invited Presentation: 

Authors