San Francisco Bay Area Seismic Velocity and Depth Profiles for Rock Types

Northern California rock formations have empirical compressional wave velocity versus depth relationships documented for constructing the USGS Bay Area Velocity Model 05.0.0. The report summarizes data for major rock types like the Franciscan Complex and provides a new polynomial relation for Holocene deposits derived from hundreds of USGS vertical seismic profile measurements. This model was developed by the USGS, converting Vp to shear wave velocity and density using established empirical rules.

Use Cases

• Model shear wave velocity (Vs) versus depth for specific rock types like Franciscan metagraywacke using the provided empirical Vp-to-Vs conversion rules.
• Calculate intrinsic attenuation coefficients (Qs and Qp) for seismic waves using the derived Vs values and the documented methodology.
• Apply the polynomial function Vp = 0.7 + 42.968z - 575.8z^2 + 2931.6z^3 - 3977.6z^4 to estimate compressional wave velocity in Holocene and Plio-Quaternary deposits for the upper 40 meters.
• Estimate rock density for crystalline formations using the Vp values and the referenced Gardner's rule and Christensen and Mooney (1995) relations.
• Validate or constrain regional seismic velocity models by comparing against the empirical Vp versus depth relationships tabulated for rock types like Salinian granite and Great Valley Sequence.

Strengths

• Relationships are derived from hundreds of measurements in USGS 30-meter vertical seismic profiles (VSPs) for Holocene deposits.
• The model covers multiple major rock formations in northern California, including the Jurassic and Cretaceous Franciscan Complex and Cretaceous Salinian granites.
• Provides a specific polynomial equation for velocity in near-surface (upper 40 m) Holocene and Plio-Quaternary deposits.

Limitations

• The specific row count for the underlying measurement data is not provided, limiting assessment of statistical robustness.
• Geographic scope is focused exclusively on the San Francisco Bay Area, limiting applicability to other regions.
• The report's publication date and the temporal range of the source VSP measurements are unknown, potentially affecting recency.

Provenance

Source

U.S. Geological Survey (USGS), as part of the development for the Bay Area Velocity Model 05.0.0.

Collection Method

Empirical analysis of vertical seismic profile (VSP) measurements and compilation of existing data for defined rock types.

Geography

San Francisco Bay Area and northern California, United States.