Short-term Variations in Earthquake Production in the Southern San Andreas Fault System Due to Lake Level Variations in Lake Cahuilla, Salton Trough, California: Implications for Short-term Slip Rate Variability
Description:
Paleoseismic data collected over the past several decades from among the major elements of the southern San Andreas fault (sSAF) system in the Salton Trough, southern California, show significant variability in earthquake production resulting from the presence or absence of the regional Lake Cahuilla. Modeling by Hill et al. (2023) demonstrate that ~100 m of water load effect the strength of the southern SAF due to variations in pore water pressure, and Rockwell et al. (2023) show that this effect also applies to the Imperial fault (IF) and elements of the southern San Jacinto fault. M7 and larger earthquakes account for most of the moment release in the sSAF system, with the majority of these larger earthquakes having occurred during periods of high lake stand on the southernmost SAF and SJF, sometimes resulting in periods of higher moment release (clusters).
The Salton Trough was dry or mostly so for at least 1 ka between about 100 BCE and 950 CE during which the system equilibrated to lower pore pressure conditions. When lakes again repeatedly filled the Salton Trough between about 950 and 1250 CE, earthquake production on the Imperial fault increased by a factor of 2 to 3 suggesting that its slip rate also increased by this magnitude. A similar burst of activity is seen on the sSAF based on reanalysis of paleoseismic data. These observations indicate that relatively small changes in water depth, such as lake level variations, seemingly innocuous differences in the water table, or the result of sea level rise from the late Pleistocene to the Holocene, can dramatically affect earthquake production on faults that are directly connect to a fluctuating water system in a fluid saturated crust.
Session: Temporally Variable Records of Earthquake Behavior and Considerations for Seismic Hazard Analyse [Poster]
Type: Poster
Date: 4/17/2025
Presentation Time: 08:00 AM (local time)
Presenting Author: Thomas
Student Presenter: No
Invited Presentation: Yes
Poster Number: 35
Authors
Thomas Rockwell Presenting Author Corresponding Author trockwell@sdsu.edu San Diego State University |
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Short-term Variations in Earthquake Production in the Southern San Andreas Fault System Due to Lake Level Variations in Lake Cahuilla, Salton Trough, California: Implications for Short-term Slip Rate Variability
Category
Temporally Variable Records of Earthquake Behavior and Considerations for Seismic Hazard Analyses