SCEC Award Number 22060 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Support of next generation Statewide Community Velocity Models through enhanced basin representations
Investigator(s)
Name Organization
Andreas Plesch Harvard University John Shaw Harvard University
Other Participants M. Peter Suess
SCEC Priorities 4b SCEC Groups Seismology, CXM, GM
Report Due Date 03/15/2023 Date Report Submitted 03/16/2023
Project Abstract
 We improved 3D descriptions of sedimentary basins in California to support the development of next-generation SCEC Community Velocity Models (CVM’s). First, we evaluated new probabilistic approaches to parameterize the basin velocity structure (Vp & Vs) using wellbore, seismic reflection, and other direct velocity constraints. This effort focused on the Los Angeles basin, which is the most data rich and mature basin velocity representation in the current CVM’s. Our analysis included formal assessment of model uncertainties as well as provide statistical measures of spatial variability in the sedimentary velocity structure. In a second phase of the project, we developed new, detailed basin surfaces for the complete Central Valley (San Joaquin and Sacramento basins) to provide for continuity and consistency in velocity modeling. The Central Valley is the largest sedimentary basin structure in California, yet is not directly represented in CVM-S or CVM-H. Development of the new Central Valley model is critical for SCEC’s efforts to move toward encompassing the entire San Andreas plate boundary system. This year we focused on improving the Central Valley basin shape. It is now represented by a top-basement surface and a detailed base Tertiary geologic horizons along its entire, ca. 650 km long extent. We also developed a database which provides the basis for developing a base Quaternary geologic horizon for the complete basin. Finally, we identified a list of wells which have extensive sonic logs and cover large portion of the Sacramento Valley.
Intellectual Merit The first component of this research examines how we consider uncertainty in velocity model descriptions and its influence on numerical simulations of seismic wave propagation. Properly understanding uncertainty, and its impact on simulations is a critical component of improving these community models. The second part of our project developed new descriptions of the Central Valley region in southern California, and area largely unrepresented in current CVM’s. Thus, our efforts are helping to improve and expand the coverage of the CVM’s in ways that will enhance their use in a range of SCEC science and hazard assessment efforts. This work also helps us take steps to expand models statewide, which is a focus of the Center.
Broader Impacts This research establishes new approaches to representing geologic structures in Community Models, including the defining of sedimentary basin velocity descriptions that can be used to develop next-generation Community Velocity Models (CVM’s). Such improvements seek to enhance our ability to forecast strong ground shaking during large earthquakes, and thus provide critical information to help protect life and property.
Exemplary Figure Figure 2: Left: A perspective view of the top of crystalline basement surface for the entire Central Valley basin. The interval of the color contours is 1000m. Letters point at major data sources: A: structure contours by Wentworth et al., (1995), B: Unruh et al. (2004), C: Brocher et al. (1994), D: Fuis & Mooney (1990); Right: A perspective view of the detailed base Tertiary surface for the entire Central Valley basin. The interval of the color contours is 500m. Letters point at major data sources: A: Well Tucker-1 (API 0408900003), B: cross-sections in CA DWR (2014), C: AAPG correlation sections (Cross et al., 1954, Edmondson et al., 1967, Rennie, 1987), D: Cherven, 2020, E: Bartow (1991), F: Walter, 1990, G: Guzofski et al. (2007), H: Wentworth et al., 1984, I: Namson & Davis, 2017