geophone

noun

1. a device that is placed on or in the ground and used to detect seismic waves.

1. An electronic receiver designed to pick up seismic vibrations on or below the Earth’s surface and to convert them into electric impulses that are proportional to the displacement, velocity, and acceleration of ground movement. Geophones detect motion in only one direction and are usually used in groups of at least three, oriented at different angles, so that a three-dimensional record of ground movement can be obtained.