Tracking Groundwater with the Ambient Seismic Field

Abstract

Aquifers are vital groundwater reservoirs for residential, agricultural, and industrial activities worldwide. Tracking their state with high temporal and spatial resolution is critical for water re- source management at the regional scale yet is rarely achieved from a single dataset. Here, we show that variations in groundwater levels can be mapped in space and time using perturbations in seis- mic velocity (dv/v). We employ the computing language Julia and cloud computing resources to make daily measurements of dv/v across California from the cross-correlation and auto-correlation of the ambient seismic field. We compare our results to estimates of groundwater from groundwa- ter wells, precipitation and satellite measurements. dv/v reproduces the groundwater level changes that are marked by the multi-year depletions and rapid recharges typical of California’s cycles of droughts and floods. dv/v correlates spatially with vertical surface displacements and deformation measured with GPS and the GRACE satellite.