Groundwater Variations From Autocorrelation and Receiver Functions

Using a 20-year continuous broadband record and two independent single-station techniques-ambient noise autocorrelation and receiver functions-we document a relationship between subsurface seismic response and groundwater levels (GWLs) in the Gulf Coast Aquifer System of southern Texas. We find that a surge of GWL following three consecutive hurricanes and documented at an adjacent monitoring well is accompanied with changes in receiver function power spectra and ambient noise autocorrelations. Using a simple physical model, we show that GWL changes should affect P- (V-P) more strongly than S-wave (V-S) velocities, consistent with our observations and previous ones based on inter-station correlations. Agreement between receiver function and ambient noise analyses shows that both can be used to reliably estimate temporal changes in subsurface properties on long timescales. Due to their sensitivity to V-P, single-station techniques respond more strongly to GWL changes, making them useful for characterizing and monitoring aquifer systems.