Assembly and Validation of a Multi-scale Community Velocity Model (CVM) for the South-central Alaska Region, SCAR-CVM V1.0

About This Grant

Eleven percent of the world's recorded earthquakes occur in Alaska, with many notable historical events including the 1964 M9.2 Alaska earthquake, the second largest earthquake ever recorded, as well as the 2018 M7.1 Anchorage earthquake. Earthquake hazards in south-central Alaska are a serious concern because the area includes the city of Anchorage where more than a third (~280,000 people) of the state’s population live. To facilitate estimating seismic hazard for the region from future large earthquakes, this project will assemble the first version of a multi-scale three-dimensional Community Velocity Model (CVM) of the subsurface of south-central Alaska. The CVM will be built with existing model components, calibrating its parameters by comparison of simulated and recorded waveforms for small local earthquakes. The CVM will be freely available to local agencies, scientists, and communities, bridging advanced modeling with practical applications such as assessing the seismic hazard to critical infrastructure in this region. The project will train a graduate student in seismic wave propagation simulation, fostering the next generation of geoscientists. The researchers plan to assemble and distribute the first version of a multi-scale Community Velocity Model (CVM) for the south-central Alaska Region, SCAR-CVM V1.0, from existing model features. The accuracy of such a CVM is fundamental to estimates of ground motions for seismic hazard analysis using physics-based wave propagation. Features in the proposed CVM will include 3-D tomographic velocity variation, high-resolution surface topography, the depth to basement in the Cook Inlet basin, generic basin velocities combined with near-surface constraints in the sediments, and a low-velocity weathering layer constrained by Vs30 values. Modeling of 0-1 Hz ground motions and comparison to seismic observations for six local M4.6-5.9 earthquakes will allow calibration of the velocity and attenuation structure in the model, as well as help assess the efficacy of the model for waveform prediction. This project will demonstrate to what extent the model can forecast geographically specific ground motion patterns such as extended durations and amplitudes, or amplification above the sedimentary basins of south-central Alaska. These are all capabilities needed for physics-based seismic hazard analysis. The work will also incorporate into the CVM the best available geometry of the subducting slab south-southeast of Anchorage, allowing future simulations of megathrust simulations such as the 1964 M9.2 earthquake, as well as intra-slab events such as the 2018 M7.1 Anchorage earthquake. The planned CVM will be the first iteration of any future improvements when new parameter constraints become available for studies such as nonlinear analysis of the soils and critical lifelines, as well as help enhance seismic risk preparedness, bridging advanced modeling with practical applications. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.