Artificial Source Frequency-Tripper Sounding Method

The natural source tipper tensor survey exists disadvantages, on one hand, the limited signal-to-noise ratio makes the field data unreliable; on the other hand, the vertical electrical sounding is more difficult than the lateral prospecting.Therefore, this paper presents the Artificial Source Frequency Tipper Sounding Method (ASFTSM), with the support of11th Five-Year project (2007CB8416608) from Department of Science and Technology, to solve the problem of high-precision tipper tensor sounding and to provide a way for precise geophysical exploration.Based on the sounding theory of artificial source, the expressions of tipper tensor of artificial source in homogeneous half space is deduced, the function of frequency tipper parameter and electrical parameter of the earth is built, the feasibility of artificial source tipper tensor sounding is theoretically proved, the restriction of arrangement of measuring points and the affect of measurement result which caused by field source sector is solved, the work area of single source is broadened, full measurement of frequency tipper in the far zone is achieved.In order to demonstrate the feasibility of frequency tipper sounding, and to derive the recurrence formula of tipper tensor of the single source and compound orthogonal artificial source in homogeneous layered media, adaptive numerical filtering technique is applied to calculate the frequency tipper response of single electric dipole source, single horizontal magnetic dipole source, orthogonal electric dipole source and horizontal orthogonal source in typical layered models, the results show that frequency tipper can effectively reflect and distinguish the electrical characteristics of layered media. The feasibility of frequency tipper tensor of artificial source is demonstrated. By comparing the sounding curves of single source and orthogonal source, the affect of field source to measurement results can be solved by multi-source polarization is proved.In order to study the response of artificial source tipper tensor to complex geological target, the ASFTSM2.5-dimensional finite element numerical method is used to simulate the response pattern of tipper tensor parameters to ASFTSM typical two-dimensional geological models. The study shows that frequency tipper can effectively reflect the vertical and horizontal change of electrical properties of complex geological body. Meanwhile, with the aid of tipper amplitude, tipper elasticity and the real induction vector and tensor tipper, geometric information such as dimension, border, tendency and spatial location of the target can be extracted to precisely position the geological body. Through numerical calculation, the responses of artificial frequency tipper and natural field Cagniard resistivity to near-surface2-dimensional low resistivity body are compared; the result shows that the static shift caused by near-surface uneven geological body based on Cagniard resistivity sounding is basically eliminated by artificial source frequency tipper sounding method.The vertical and horizontal detective ability of ASFTSM is studied through theoretical and numerical calculation, the result shows that ASFTSM not only has the ability of detecting lateral heterogeneous geological body but also has longitudinal electrical resolution, it is especially sensitive to low resistivity geological body. Also, the field source, measurement, survey scope, observing program, resolution, topographic effect and applicable condition of ASFTSM are studied and summarized, technical programs such as reinforcing the natural field through adding artificial source, tipper tensor measurement, full observation in the far zone are proposed. Field tests using the assembled ASFTSM transmit and receive system at Moon Island of Changsha and Zhaoyuan Shandong show the validity and prospects of ASFTSM in metal ore exploration.Through a series of research in the paper, the theoretical foundation, techniques, data processing and interpretation of ASFTSM are established. ASFTSM is a new method of geophysical exploration, providing a way for accurate geophysical prospecting.