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Simulation of CSAMT static effect and research on its characteristics in homogeneous earth |
HU Rui-Hua, LIN Jun, SUN Cai-Tang, LIU Chang-Sheng, ZHOU Feng-Dao |
College of Instrument Science and Electrical Engineering, Jilin University, Changchun 130061, China |
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Abstract Uneven electric body near the ground surface interferes the target field, which is called static effect that is regarded as one of the noises of deep exploration. In order to deeply understand the static effect, the authors simulated respectively the ground surface responses of axial and asides observation methods on the conditions of taking homogeneous earth as model background and Cagniard apparent resistivity as explanation parameter. Some conclusions have been reached:(1) The effects of static characteristics of the two observation methods are consistent. (2) The interference is maximum for measuring points above the anomaly body. On the contrary, the interference is minimum for the points which stay away from the anomaly body. (3) Low resistivity abnormal body causes the contours of the interference area to become concave. The resistivity is lower. High resistivity abnormal body causes the contours of the interference area to become convex. However, changes of contours into convexity are not obvious although the resistivity of anomaly body is enlarged. Both low resistivity abnormal body and high one cause the mid-low frequency contours to become nearly erect in the interference area; (4) The static effect of low resistivity causes the standard curve to be parallel downward in mid-low frequency, but in high frequency the extent of the standard curve paralleling downward depends on low resistivity value, the lower the resistivity is, the less parallel the standard curve downward is, because of stronger electromagnetic induction for lower abnormal body which is superimposed upon the static effect. However, the static effect of high resistivity causes the standard curve parallel upward in full frequency, which is consistent with previous conclusions. The results can provide a reference for the identification and improvement of static effect correction algorithm and hence has a certain theoretical and practical value.
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Received: 26 November 2014
Published: 10 December 2015
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