A geophones is a sensitive ground motion transducer that converts ground movement into electrical signals. A geophone is used by seismologists and geophysicists to measure the wave signals that are generated in response to seismic waves.
As the seismic waves propagate downward, they are reflected or refracted off layers in the subsurface. The output data is recorded on geophones and compiled and processed by a seismograph.
These signals are later analyzed for studying the earth's structure and for determining in-situ stress measurements in rocks.
Trenchlesspedia Explains Geophone
Geophones have low-resonance frequency to measure low-frequency signals. A geophone consists of a mass suspended on springs. When velocity is applied at frequency lower than the resonance frequency, the suspended mass begins to move. The mass will remain stationary for frequencies greater than the resonance frequency.
While conducting a seismic refraction survey, low-frequency seismic energy is produced by a seismic source on the surface such as a hammer plate, buffalo gun or weight drop, depending on the depth of penetration required and prevalent site conditions.
As the seismic waves propagate downward, they are reflected or refracted off layers in the subsurface. 24 or 48 geophones arranged at regular intervals of 1 to 10 meters detect these refracted seismic waves. The output data from the geophones is compiled and processed by a seismograph.
The seismic trace components include direct wave, reflected wave and critically refracted wave.