seismografer

Seismografer are instruments used to detect and record ground motions caused by earthquakes, volcanic activity, explosions and other dynamic processes within the Earth. They are central to seismology, helping scientists determine the size, location and mechanism of seismic events and to monitor ongoing activity.

A seismograph typically consists of a sensor, or seismometer, connected to a recording system. The seismometer uses a mass that moves relative to the Earth’s surface as ground motion occurs, generating an electrical signal that is proportional to acceleration. Modern systems commonly employ three-component sensors that measure motion in vertical and two horizontal directions. The recording system logs the signal as a seismogram with a time reference. Early seismographs produced mechanical traces on paper or ink on drums, while contemporary instruments are digital and can store data locally or transmit it to central networks.

Types of seismografer include analog (mechanical writing) instruments and digital broadband seismographs capable of capturing a wide range of frequencies. Some sensors are designed for strong-motion to withstand large ground forces near major earthquakes. The data from seismografer enable the estimation of earthquake location, depth, magnitude, and faulting style, as well as the monitoring of volcanic activity and the operation of early warning systems.

The development of modern seismography began in the late 19th and early 20th centuries, with continuous improvements in sensors, recording methods and global networks. The word seismograph comes from the Greek seismos, meaning quake, and graphein, meaning to write.