Terme préférentiel

Seismograph

Description

Instrument that detects and records ground motions (and especially vibrations due to earthquakes) along with timing information. It consists of a seismometer, a precise timing element, and a recording device or data logger.
To avoid the strong ambient noise caused by ocean waves (microseisms), two types of seismograph have traditionally been used to record seismic signals: one for periods longer than about 10 s and the other for those shorter than 3 s. However, this kind of filtering may result in significant signal distortions and underestimation of earthquake magnitude. A broadband seismograph can record faithfully seismic signals in a frequency range of 3 decades or some 10 octaves (e.g., between 0.1 s to 100 s) or even wider, thanks to the improved linearity range of the seismometer and dynamic range of the recorder