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Abstract

Groundwater withdrawal for domestic, industrial, and agricultural consumption has intensified in Santa Ana Basin, California. It’s imperative to monitor the hydraulic head for groundwater management and the sustainability of water resources. Observation wells provide direct information on groundwater level. However, the sparse spatial coverage makes it inappropriate for large-area studies. Satellite-based remote sensing observations, such as the GRACE/FO data, can obtain regional groundwater storage. Nevertheless, it has coarse spatiotemporal resolution and suffers non-uniqueness between water volume and aquifer depths. Recently, the seismic velocity change (dv/v) calculated by the cross-correlation of ambient seismic time series has been adopted to reveal the groundwater level change. The dv/v has the advantage of illustrating the purely elastic response of the aquifer. Here, we measure the dv/v change at eleven seismic stations from 2000 to 2022 to study the spatiotemporal variabilities of groundwater levels in the Santa Ana basin. Our results manifest good consistency with observed groundwater levels with a correlation coefficient reaching up to 0.8, which means dv/v can reveal both long-term and seasonal fluctuations. Furtherly, the dv/v showed great agreement with precipitation data, which means the groundwater levels in the Santa Ana basin are modulated mostly by the rainfall pattern. As an independent measurement, dv/v shows great promise for regional groundwater study.