Seismic surveys looking for oil and gas use what’s called a thumper truck, which literally thumps the ground to send seismic signals through the Earth. Those signals are received by seismometers some distance away. Geologic structures underground are detected by the way they reflect, bend and otherwise change the thumper truck’s seismic waves.

When seismologists perform these surveys near sand dunes, however, they notice their signals are not coming through clearly.