Study On The Phenomenon Of Static Displacement In CSAMT

Controlled source audio frequency magnetotelluric method (CSAMT) developed on the basis of the magnetotelluric method (MT) and audio frequency magnetotelluric method (AMT) is an artificial emission source electromagnetic sounding method.MT field source using the ionosphere as the incident electromagnetic wave excitation signal, AMT make use of lightning as the incoming electromagnetic wave excitation signal, the two do not need a large emission source equipment, the equipment more portable. As the excitation source is weak, MT and AMT observations are small too. Collecting data need long superimposed time, while not suppress the industrial electricity and electrical interference from the air, thus contributing to find a geophysical methods that has strong anti-jamming capability, which using controlled source and by changing the frequency for sounding. University of Toronto in Canada in 1971, this interference better and faster exploration stacking methods (namely CSAMT) came into being.CSAMT has a wide range of applications, in the mining, geothermal, water, oil and gas exploration work in a role to play, and have achieved good results. However, MT originally had a static displacement problem (also called static effects) also exists in CSAMT, it became one of several major problems in CSAMT processing and interpretation, seriously affecting the credibility of the exploration results. Therefore, the static correction in CSAMT data processing and interpretation has become an indispensable step.Static shift correction needs to be clear the physical nature of the phenomenon that produced static displacement. As there is the small-scale electrical heterogeneity near-surface, the current distribution underground media distorted, making the ground field observations curve displaced up or down with the same shape, while the phase curve of the same, leading to apparent resistivity curves change in same form of upward or downward displacement along the resistivity axis. This combination of Maxwell's equations under the boundary conditions, analysis of the static displacement mechanism for the generation and use program demonstrates static shift forward, static shift identification and the correction of static displacement. The static displacement correction should firstly to correctly identify whether it contains static displacement data (abnormal data and the static effect should be distinguished), then choose the reasonable correction method to correct the data. Domestic and foreign literature data indicate that static shift correction methods are curves translation, spatial filtering, median filtering, the phase method, the magnetic field measured data calculate the resistivity, wavelet analysis method. The paper show by model median filtering and curves translation correction is the ideal result.Most of the time, static displacement in our exploration work is harmful. The static correction to eliminate the interference of the static displacement is needed. In some cases, such as theory researching, Static displacement may also be an better exploration method in exploring the non-uniform electric properties of shallow geological, in which only a theoretical study.In practical CSAMT data processing, select the CSAMT data near a copper mine, including the phenomenon of static shift of a lot more serious. Static correction eliminate the static effect effectively (low resistivity caused the static displacement in the area), avoids some of the static shift effect interpreted as resulting from abnormal deep faults.