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Seasonal and Long-Term Groundwater Unloading in the Central Valley Modifies Crustal Stress
G Carlson1, M Shirzaei1, S Werth1,2
1School of Earth and Space Exploration Arizona State University Tempe AZ USA.
Journal of Geophysical Research. Solid Earth
|November 9, 2020
Summary
Groundwater depletion in California
Area of Science:
- Geophysics
- Hydrology
- Seismology
Background:
- Terrestrial water storage changes cause Earth's crust deformation, influencing crustal stress and seismicity.
- Groundwater is a key factor in California's water storage fluctuations and drought-induced water loss.
Purpose of the Study:
- To investigate the impact of groundwater volume changes on crustal stress evolution in California's Central Valley.
- To assess the accuracy of existing models in capturing groundwater's contribution to terrestrial water loading.
Main Methods:
- Utilized high-resolution Interferometric Synthetic Aperture Radar (InSAR)-based vertical land motion data to estimate groundwater volume loss.
- Applied GPS-derived elastic load models for comparison with InSAR data.
- Calculated Coulomb stress changes at seismogenic depths.
Main Results:
- Groundwater unloading during the 2007-2010 drought induced Coulomb stress changes up to 5.5 kPa.
- Seasonal groundwater fluctuations caused stress changes up to 2.6 kPa at seismogenic depths.
- Faults near the Central Valley experienced the most significant stress changes, while the San Andreas Fault showed minimal impact.
Conclusions:
- Groundwater loading contributes to non-tectonic fault loading, particularly near the Central Valley.
- Existing GPS-derived models may underestimate crustal stress changes due to groundwater fluctuations.
- Groundwater's influence on California seismicity is localized and not a dominant modulating factor due to rapid stress decline with distance.
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