In geophysics, a geophone is a transducer for converting ground motion to an electrical impulse for the purposes of recording. In plain English, a geophone is similar to a microphone or stethoscope that is specialised for recording vibrations in the ground. In the geophysics industry, geophones are generally referred to as 'jugs.'

Geophones are distinguished from seismometers in that they cannot be calibrated. A seismometer may be presicely calibrated so that a voltage produced by the seismometer can be translated directly to ground motion. Geophones have no capacity for calibration, and are used in situations where the exact earth-motion is of little interest. Geophones also typically record higher-frequency signals than seismometers.

Geophones are typically built to be rugged and cheap, and deployed in large arrays for reflection or refraction geophysical exploration. Most geophones only record ground motions in the vertical direction (called z-component geophones. Some geophones record all three components of ground motion.

Most geophones are a composed of a small, jug-shaped section (hence the name) attached to a metal spike, which is driven into the ground. This is typically done by pushing the spike into the ground, and then steping on it with the heel of your boot ("stomping jugs" is not something you want to do wearing tennis shoes, from personal experience). Geophones are often specialized for the environment where they will be used. Hydrophones are specialized for towing behind boats for off-shore exploration (the term is also used for any underwater microphone), and 'swamp jugs' are specialized for use in wetlands.

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