SCEC Award Number 25270 View PDF
Proposal Category Collaborative Research Project (Multiple Investigators / Institutions)
Proposal Title Fault architecture, geomorphic expression, and mineralogy of the Northern Calaveras Fault
Investigator(s)
Name Organization
Christie Rowe University of Nevada, Reno Rich Koehler University of Nevada, Reno
SCEC Milestones A1-3, A2-2, A3-1, A3-4, B1-1, B2-1 SCEC Groups Geology, PBS, CEM
Report Due Date 03/15/2026 Date Report Submitted 03/16/2026
Project Abstract
 The San Andreas plate boundary in the San Francisco Bay Area shares slip across a set of sub-parallel dextral faults, some of which creep either at constant rates or episodically. The Calaveras Fault is the continuation of the creeping section of the San Andreas Fault which moves steadily at approximately the farfield plate rate south of Hollister. North of Hollister, the San Andreas fault is apparently locked, and slip continues on the Calaveras Fault, the slip rate decaying northward until becoming undetectable north of Danville, 115 km along strike. The Northern Calaveras fault has hosted several recent M6 earthquakes, but there is no geologic slip rate reported. This is an excellent natural laboratory for answering two questions with broad implications: first, can the field characteristics or geomorphic expression of creeping faults be distinguished from those who only slip seismically? Second, are there any geologic factors (fault structure, fault rock mineralogy, or wall rock characteristics) that can help explain the rapid decay in current creep rate along strike? To answer these questions, we propose a multi-pronged study to synthesize existing literature including consultant reports, detailed mapping of geomorphic features in Lidar DEM followed by field mapping. Outcomes at the end of year 1 include: a detailed fault trace map for the Northern Calaveras with documentation of geomorphic and geologic indicators of faulting, identification of along-fault sedimentary deposits favorable for paleoseismic investigations and potential geologic slip rate records, and a preliminary lithologic / structural map of the wall rock in the central Northern Calaveras.
Intellectual Merit Creep on potentially seismogenic faults may accommodate some of the slip rate over geologic time, affecting estimates of slip deficit that are critical inputs to seismic hazard estimation. Instrumental records of fault creep in the San Francisco Bay area reach back at most a few decades, showing that the creep rates are variable and sensitive to changes triggered by nearby earthquakes and other phenomena, so cannot be confidently projected back in time. By investigating the landscape, textural, and mineralogical signatures of creep, we aim to provide geologists with better tools for interpreting creep history on faults.
Broader Impacts This study has produced novel primary observations that will contribute to enhancing our understanding of the role of fault creep in hazard models, which will be communicated to the research community and practitioners through conference presentations and open access publication. In addition, Hannah Martin, a Ph.D. student with primary responsibility for this project, has gained valuable research experience as well as two other graduate students who have assisted in the field (Maggie Duncan and Alex Travers, all female students in a traditionally underrepresented field). Hannah’s experience on this project contributed to her securing a 2026 summer internship with LCI.
Project Participants The work described here was substantially completed by UNR Ph.D. student Hannah Martin with support and supervision, including in the field, from the PIs Christie Rowe and Rich Koehler. Field assistant support also enabled two other graduate students studying paleoseismology /neotectonics to spend time mapping in the Calaveras Fault: Alex Travers (U. Otago) and Maggie Duncan (Desert Research Institute). We were fortunate to be accompanied by Ben Curry (Santa Clara County Parks Archeologist) whose local knowledge helped inform our work and whose support we have secured for the forthcoming trenching permit application.
Exemplary Figure Figure 3: Hillshade images showing the process of improving the fault trace maps in the Calaveras
fault. A: Existing Quaternary Faults and Folds Database (Bryant & Cluett, 1999) fault strands, fault
54a, central Calaveras. B: Identified geomorphic indicators. C: Interpreted fault map.
Linked Publications

Add missing publication or edit citation shown. Enter the SCEC project ID to link publication.