A geologic survey system includes a plurality of acoustic sources spaced at intervals over a target area of a terranean surface. Each of the plurality of acoustic sensors is configured to generate a seismic energy wave. The system also includes a plurality of acoustic sensors positioned in a plurality of boreholes formed in a geologic formation, where the boreholes have a depth sufficient to reach a geologic datum. The system also includes a control system communicably coupled to the plurality of acoustic sensors and configured to perform operations including receiving, from the plurality of acoustic sensors, data associated with reflected acoustic signals generated by the plurality of acoustic sources and received by the plurality of acoustic sensors; determining, based on the received data, a subsurface topology of the geologic formation; and generating a subsurface model of the geologic formation based on the determined subsurface topology.