an instrument used in seismic exploration and designed to pick up mechanical oscillations of the ground and convert them into electrical oscillations. Inertial sensors are used for work on land. A common type is an electro-dynamic sensor with natural frequencies of 0.5–40 Hz and with aperiodic critical damping. There are vertical and horizontal seismic sensors. Vertical sensors, which primarily record compressional waves (P waves) arriving from below, are used most often. Horizontal types are used to record shear waves (S waves). A three-component sensor consisting of a vertical sensor and two horizontal sensors in a single housing is used to study the total vector of ground displacement.
Ceramic piezoelectric pressure sensors are used at sea. They become electrically polarized when an elastic wave causes a change in the external pressure applied to the sensor. Such sensors are placed inside a special hose, which is towed by a ship. Hermetically sealed, electrodynamic sensors are usually used for integrated seismic well logging. They are equipped with electronic amplifiers for preliminary amplification of the weak electrical oscillations transmitted by cable up from the well.
I. I. GURVICH