Seismic noise

In seismology and seismic noise means any accidental and unwanted signal components that are recorded at a measuring point along with the desired user signal by the measuring instrument.

Since the earthquake or artificially (eg blasting) excited seismic waves are usually very weakly with increasing distance, the noise affects usually from distracting and hinders the evaluation of the data obtained.

Causes

Seismic waves are recorded as vibration or movement of the earth. Originally, the seismic noise was the noise, therefore, meant that is not caused by the source signal. The ground is almost always in trouble, because any mechanical influence of the soil generates seismic energy. This can be done by natural as well as artificial influences.

Natural sources include weathering: Sun, wind may be about to act directly on the ground or tall objects (trees, poles, etc.) them into vibrations that transmit on the floor and be propagated. However, the ground motion is also produced eg from direct sunlight when the ground or rocks to warm and expand.

One of the predominant sources of natural seismic noise represents the sound of the sea, which is generated by running onto the coastal waves and surf. But the tides, air pressure fluctuations or seasonal temperature differences lead to long-periodic deformations of the soil according to the low frequency noise trigger.

In addition, there are also artificial sources, which go back to the influence of man and technology: shock about by machinery, road or rail transport, technical devices or people that move a short distance from the measuring instrument. A common source of noise in the use of explosives for signal excitation, for example, the air-borne noise, which may be close to the source particularly pronounced.

Since seismological measurements in modern times are usually done with digital technology, the term noise and interference caused by the operation of the meter itself includes but additionally ( instrument noise, see also: Noise ( physics ) ) or by externally applied electromagnetic fields arise. So can influence the modern highly sensitive instruments such as high -voltage power lines over several hundred meters.