Using Ambient-Noise Based Ellipticity and Delay Times to Probe Groundwater Changes in Southern California

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

In recent years, a dramatic and unsustainable mining of groundwater, our largest fresh water source, has taken place in the western US, with depletion rates currently at their highest. Paired with periods of drought in as much as a third of the contiguous US, the monitoring of groundwater resources is increasingly important. How do aquifers respond to stresses such as increased withdrawal rates and droughts? What does the end of a drought mean for groundwater availability? We employ temporal monitoring of ambient-noise-based horizontal-to-vertical amplitude measurements (H/V, or ellipticity) and delay times of Rayleigh waves to reflect changing conditions within the shallow subsurface. Both types of measurements are promising for monitoring changes at shallow depths relevant to groundwater, and they are complementary in their relative sensitivities to the near-sensor and integrated-path structure between sensors, respectively. We present results of this analysis for southern California for 2000-present using data from stations in the CalTech Regional Seismic Network. Notable features observed are long-term changes in H/V interpreted to be groundwater signals and seasonal variability in H/V from a variety of sources.

Presenting Author: Ellen M. Syracuse

Authors