Seismic sensing to monitor changes in groundwater storage in California’s Central Valley

We propose to use seismic interferometry to monitor changes in groundwater. Seismic interferometry is a sensitive technique that uses the background seismic field, which is always present in the Earth, to track very small changes in seismic velocity of less than 0.1%. These velocity variations are sufficiently sensitive that they can reflect changes in groundwater. With a distributed seismic network, we can image the geographical extent of those changes. Their frequency variation is sensitive to the depth of the changes, and the lapse time into the seismogram is sensitive to the total volume sampled. Together these allow a sort of tomography that results a reconstruction of the distribution of these changes with only a modest number of seismic stations. We demonstrated that the atmospheric river storms of 2023 had a limited impact on the recovery of aquifers in the Los Angeles area. Mao et al. (2025) demonstrated and validated seismic sensing of groundwater for the Los Angeles Area. We propose to deploy 12 trillium intermediate seismometers to create analogous images for the Kaweah Basin of California’s Central Valley. We would begin by permitting and installing the stations, after which we would systematically analyze the data, which involves the correlation of continuously wavefields recorded at all stations with all other stations. We will follow (Mao et al., 2025) to measure the time-dependence of the velocity change and will map out 4D variations (3 spatial dimensions plus time) in groundwater in the Earth’s crust. We propose to make these measurements over at three annual cycles to confirm that we can faithfully recover the signal of interest and resolve inter-season variability. Mao, S., W. L. Ellsworth, and G. C. Beroza (2025) Depth-dependent seismic sensing of groundwater recovery from the atmospheric-river storms of 2023, Science 387, 758-763.