SCEC Award Number 11193 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Deep Structure of the Southeastern NewportInglewood and Compton-Los Alamitos Faults
Investigator(s)
Name Organization
Robert S. Yeats Earth Consultants International Danielle M. Verdugo Earth Consultants International
Other Participants
SCEC Priorities A3, A9, B1 SCEC Groups Geology, USR
Report Due Date 02/29/2012 Date Report Submitted N/A
Project Abstract
 Recent structural models for the Los Angeles (LA) Basin attribute deformation along the Compton-Los Alamitos fault (CLA) to fault-bend folding above a NE-dipping ramp rather, than to a shallow fault propogation fold. Our discovery last year of repeated stratigraphic sections on oil well logs across the northwestern CLA, however, support the latter interpretation. To test whether the fault we observe represents a significant structure, rather than localized fold-related faulting, we focused our efforts this year on confirming our earlier work, and extending our study to the southeastern CLA. Analysis of new exploratory well data, petroleum industry seismic lines, and cross-sections of seismicity across the southeastern CLA reveal a complex fault that cannot be explained by folding. Newly relocated seismicity by Yang and Hauksson reveal primarily reverse focal solutions below this section of the CLA. South of the LA River, seismic lines and well data reveal truncated reflectors up to depths of 5-1.5 km and gently warped basinal stratigraphy, exhibiting less apparent vertical separation than observed on the northwestern section of CLA. This southeastern section of the CLA also corresponds to the easternmost extent of uplift measured by Gilluly and Grant after the 1933 Long Beach earthquake. Its proximity to the eastern boundary of this coseismic uplift and the oblique strike-slip focal mechanisms calculated by Yang and Hauksson suggest a structural connection between the southeastern extent of the CLA and NIFZ, implying a strain-partitioning relationship between the two faults.
Intellectual Merit Our work improves and evaluates the Community Fault Model (CFM) to consider strain partitioning between reverse‐slip and strike‐slip faults in LA Basin. We have found evidence of a structural relationship between the Newport Inglewood and Compton - Los Alamitos fault.
Broader Impacts Prior to our work, the Compton - Los Alamitos fault was poorly characterized, despite underlying one of the densest urban areas in southern California. Placing it in structural context with the Newport-Inglewood and associating it with a historical earthquake redefines the seismic hazard posed by this complex fault system.
Exemplary Figure Figure 3 Seal Beach-San Gabriel River lines cross-section with Gilluly and Grant uplift across the southeastern CLA