What Does Seismic Trace Components Mean?
The seismic trace components include direct wave, reflected wave and critically refracted wave. Wave refraction occurs at interfaces where the lower layer has greater seismic velocity than the overlying layer in near-surface site investigation.
Seismic reflection and refraction are used for mapping sub-surface geology and use laws of optical wave reflection and refraction when the waves come in contact with two different media.
Trenchlesspedia Explains Seismic Trace Components
In seismic refraction test, low-frequency seismic pulses are generated using a buffalo gun, weight drop, hammer-plate or explosives, depending on the depth of penetration required. The output from the geophones that record these waves is compiled and processed in a seismograph. The seismic trace has three basic components namely, direct wave, reflected wave and critically refracted wave.
The first seismic wave to arrive at the geophone position is the direct waves, and after a critical distance from the source of the waves, the refracted waves arrive first. The measurement of the waves that arrive first is very critical for interpretation purposes to calculate the seismic velocities of the different layers and the depth of refracting interfaces.