Suite of Regional Seismic Velocity Models for the U.S. Atlantic and Gulf Coastal Plains (CPVMv2.0): Incorporating Epistemic Uncertainty in Velocity Models

Abstract

The U.S. Atlantic and Gulf Coastal Plain (CP) sediments are kilometers‐thick, low‐velocity deposits underlain by high‐velocity bedrock that create regional patterns of amplification and attenuation of ground motions. Capturing these effects is challenging because of the limited subsurface information available, particularly the shear wave velocity ( V S ) structure down to bedrock (or assumed reference rock condition) and the associated uncertainties. This paper introduces a new suite of regional velocity models for the CPs, called CPVMv2.0, which builds upon previous efforts integrating geology, V S measurements, and sediment thickness in the region. CPVMv2.0 uses 750 measured V S profiles and identifies nine surficial‐geologic‐age‐based and geography‐based groups (with alternative physiographic‐province‐based subgroupings) to create surface‐based median V S profiles. This suite of new models also includes six subsurface‐based median profiles developed using geologic age boundaries from depth‐dependent stratigraphic sequences extracted from the U.S. Geological Survey National Crustal Model. In addition to quantifying aleatory variability in sediment velocity, weathered‐rock velocity, bedrock velocity, and the depth to the top of weathered rock and bedrock, CPVMv2.0 provides alternative profile models that allow for the characterization of the epistemic uncertainty. This is a unique and relevant feature of CPVMv2.0. Our suite of models was validated using measured and estimated fundamental resonant frequencies as well as other V S models in the region. CPVMv2.0 enables the incorporation of crustal velocities (and their associated variability and uncertainty) into physics‐based ground‐motion simulations in the eastern United States and into the development of new ground‐motion models aiming to characterize systematic site effects via V S30 , depths to V S isosurfaces, and/or sediment thickness in the region.