Seismology instruments

320px|thumb|Kinemetric seismograph

thumb|upright|140px|Geophone (SM-24), frequency band 10 Hz to 240 Hz, standard resistance 375 Ω A geophone is a device that converts ground movement (velocity) into voltage, which may be recorded at a recording station. The deviation of this measured voltage from the base line is called the seismic response and is analyzed for structure of the Earth.

thumb | right | Sketch of an accelerograph by Marcel DeprezAn accelerograph can be referred to as a strong-motion instrument or seismograph, or simply an earthquake accelerometer. They are usually constructed as a self-contained box, which previously included a paper or film recorder (an analogue instrument) but now they often record directly on digital media and then the data is transmitted via the Internet.

thumb|250px|Distortion seismometer A strainmeter is an instrument used by geophysicists to measure the deformation of the Earth. Linear strainmeters measure the changes in the distance between two points, using either a solid piece of material (over a short distance) or a laser interferometer (over a long distance, up to several hundred meters).

thumb|right|A tiltmeter on Mauna Loa, used to predict eruptions by measuring very small changes in the profile of the mountain.

seismometer developed by Harry Oscar Wood & John August Anderson

seismometer that is designed to record the earth motion under oceans and lakes from man-made sources and natural sources