Using microgravity and passive seismic methods jointly to explore the Brazos River Alluvium Aquifer.

This study used a combined passive seismic (HVSR) and microgravity method to estimate depth to bedrock, alluvial composition, and saturated thickness throughout the Northern Segment of the Brazos River Alluvium Aquifer. Previous borings and confirmation borings drilled in this study suggest this method was able to estimate depth to bedrock with an average error of 21% throughout the study area and was able to indicate trends in changing alluvial composition along each transect. Surveys were completed over eight transects at five sites within the Brazos River Alluvium aquifer in McLennan and Falls County, TX. In all, 202 passive seismic and 342 microgravity measurements were obtained. The combined passive seismic (HVSR) and microgravity method can be used to estimate depth to bedrock and alluvial composition with medium resolution (several meters) over transects of medium spatial extent (hundreds of meters to several kilometers).