MUSCAL - The Multi-Scale P and S Seismic Velocity Models of California and Western Nevada

MUSCAL: The Multi-Scale P and S Seismic Velocity Models of California and Western Nevada

Overview

The MUlti-Scale CALifornia (MUSCAL) velocity model provides a high-resolution, integrated 3D description of Vp and Vs structures across California and western Nevada. Building upon the CANVAS base model (Doody et al., 2023), MUSCAL assembles multiple regional and local seismic datasets into a single, unified framework. It effectively captures geological features across scales, from broad crust-mantle interfaces to fine-scale sedimentary basin geometries.

Key Features & Methodology

• Data-Informed Refinement: The merged multi-scale structure underwent a rigorous validation process using wavefield simulations of small seismic events.

• Optimized Near-Surface: A defining feature of MUSCAL is the inclusion of a locally optimized Low-Velocity Taper (LVT). This component is specifically engineered to represent under-resolved shallow structures, significantly improving the precision of high-frequency ground-motion predictions.

• Surface-Relative Coordinate System: MUSCAL utilizes a "squashed" vertical coordinate system where depth = 0 m represents the solid surface (topography or bathymetry). Because the model is not hard-coded to a specific Digital Elevation Model (DEM), it offers maximum flexibility for researchers to map the velocity structure onto their own numerical meshes.

Technical Specifications

• Format: Distributed as a single, self-describing NetCDF-4 file.

• Horizontal Resolution: 0.01° (~1 km) regular geographic grid (longitude/latitude).

• Vertical Resolution: Variable depth sampling to optimize resolution in the near-surface.

• Interoperability: The regular grid structure is designed for high-performance interpolation, making it ideal for constructing large-scale 3D numerical models for various applications. 

Dataset Specifications

• Coordinate System: Geographic (WGS84)

• Vertical Datum: Depth in meters (m) below the surface/sea level.

• Data Format: NetCDF-4 (.nc)

• Total Grid Points: 1,251 x 1,301 x 210

Variables

The following 3D arrays are included in the file:

Dimensions

• longitude: 1301 points

• latitude: 1251 points

• depth: 210 points (values provided in meters)