Geology and Geomorphology of the Creeping Central Calaveras Fault
Description:
The Calaveras Fault creeps rapidly at its southern end where it inherits slip from the San Andreas fault around Hollister, California. The creep rate declines to the north until it is essentially zero around San Ramon, California. The central section of the fault has generated several historical M5 - M6 earthquakes in spite of a high rate of continuous to episodic creep. We report new remote mapping and field observations of the central Calaveras fault in the vicinity of Coyote Lake and Anderson Lake. In this section, the Calaveras fault juxtaposes stratified Great Valley Group sediments against unstratified Franciscan Complex rocks of mixed lithology. In the central Calaveras, a single fault strand appears to be accommodating creep. Surface outcrops of the creeping strand reveal a ~10 m-wide zone of weathered and foliated reworked clay–rich gouge, with green serpentinite-rich bands and wider black bands apparently derived from Great Valley shales. The trace of this main strand shows evidence of recent and exhumed carbonation, in the form of travertine terraces in Coyote Creek, exhumed listvenites in ultramafic to mafic host rocks, and carbonate-cemented breccias representing recent seep deposits in the presently dry bed of Anderson Lake.
The current creeping strand is one of several geomorphically young fault strands spanning a zone up to ~1 km wide. Most of the fault strands evident in the geomorphology are west of the current creeping strand, cutting the Franciscan Complex. Following recent work (Adam, et al. 2023 and Scott, et al. 2025), we mapped geomorphic indicators of faulting and their relative confidence and certainty along the central Calaveras. Preliminary statistical analysis indicates that some bedrock compositions exert a strong control on the presence, type, and prominence of some geomorphic indicators. Ongoing investigations will reveal whether the geomorphic signals of bedrock geology dominate, or whether the currently creeping strand has a distinct geomorphic expression relative to nearby recently active fault strands.
Session: The Landscape Record of Earthquakes and Faulting - III
Type: Oral
Date: 4/16/2026
Presentation Time: 02:15 PM (local time)
Presenting Author: Christie D. Rowe
Student Presenter: No
Invited Presentation:
Poster Number:
Authors
Hannah Martin hannahmartin@unr.edu University of Nevada, Reno |
Christie Rowe Presenting Author Corresponding Author rowec@unr.edu University of Nevada, Reno |
Richard Koehler rkoehler@unr.edu University of Nevada, Reno |
Maggie Duncan maggie.duncan@dri.edu Desert Research Institute |
Alex Travers ahstravers1@gmail.com University of Otago |
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Geology and Geomorphology of the Creeping Central Calaveras Fault
Category
The Landscape Record of Earthquakes and Faulting