SCEC Project Details
| SCEC Award Number | 24005 | View PDF | |||||
| Proposal Category | Individual Research Project (Single Investigator / Institution) | ||||||
| Proposal Title | Combining Erosion Rates with Mechanical Models to Evaluate Slip Rates along the Concord-Greenville Fault System in the Vicinity of Mount Diablo, California | ||||||
| Investigator(s) |
|
||||||
| SCEC Milestones | A1-3, A2-2, A3-4 | SCEC Groups | Geology, Geodesy, PBS | ||||
| Report Due Date | 03/15/2025 | Date Report Submitted | 06/23/2025 | ||||
|
Project Abstract |
This project combines millennial-scale erosion rates with mechanical boundary element models to estimate fault slip rates within the Mount Diablo restraining step of the Concord-Greenville fault system. Our approach uses cosmogenic ¹⁰Be measurements from river sediments to determine basin-averaged erosion rates, which serve as proxies for rock uplift rates under appropriate geomorphic conditions. These uplift rates are then inverted using three-dimensional boundary element models to constrain slip rates along both the strike-slip Concord-Greenville faults and the blind reverse faults that accommodate shortening within the restraining step. We have successfully completed the mechanical modeling phase, creating detailed fault geometries and computing Greens functions that relate boundary motions to uplift patterns throughout the Mount Diablo region. River sand samples from five strategic watersheds around Mount Diablo have been collected and are currently undergoing cosmogenic sample preparation. While challenging due to the low quartz abundance in Franciscan lithologies, sample processing is nearing completion after which analysis at Lawrence Livermore National Laboratory will proceed. Once erosion rate measurements are complete, we will rapidly invert these data to estimate millennial-scale slip rates along the target structures and compare these with geodetic observations. This work provides a framework applicable to other similar structures throughout the San Andreas fault system. |
| Intellectual Merit | his project develops methodologies integrating millennial-scale cosmogenic erosion rates with boundary element mechanical models to constrain fault slip rates in restraining steps. The approach maps regional plate motions to local uplift patterns, enabling inversion of landscape evolution data to extract tectonic information. This approach may be valuable for studying blind fault systems and distributed deformation zones. The methodology directly addresses SCEC objectives A1-3 and A3-4 by providing new tools for constraining long-term fault behavior where conventional approaches are challenging to apply. |
| Broader Impacts | The project establishes methodologies combining Stanford's Cosmogenic Isotope Laboratory capabilities with computational modeling. The integrated approach provides essential baseline observations supporting SCEC's earthquake preparedness mandate. Aaron Steelquist received specialized training in both cosmogenic sample preparation. Results will directly inform regional seismic hazard models for the San Francisco Bay Area, contributing to public safety through improved understanding of fault system kinematics and earthquake potential. |
| Project Participants |
George Hilley Aaron Steelquist |
| Exemplary Figure | Figure 1: (left) Map of the study location in the eastern San Francisco Bay Area, CA. The Concord and Greenville faults accommodate ~4 mm/yr of the Pac-NA plate motion as they undergo a left step that localizes contraction within the restraining step. Uplift generated within this restraining step is accommodated along a series of blind reverse faults. The five sample watersheds are shown as W1--3, S1, and E1. (right) Long-channel profiles for the five basins flanking Mount Diablo. The stars in each profile show the along-channel position of samples that were collected. |
|
Linked Publications
Add missing publication or edit citation shown. Enter the SCEC project ID to link publication. |
|
