Estimation of the depth and structural index of 2D magnetic anomalies using improved analytic signal method
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Article Type:
Research/Original Article (دارای رتبه معتبر)
Abstract:
Summary: This paper presents a new method for interpretation of two dimensional (2D) magnetic anomaly data. The new method uses a combination of analytic signal and its total gradient to estimate the depth and nature -i.e. structural index- of an isolated magnetic source. However, the proposed method is sensitive to noise. In order to lower the effect of noise, upward continuation technique is applied to smooth the anomaly. Tests on synthetic noise-free and noise-corrupted magnetic data show that the new method can successfully estimate the depth and nature of the causative source. For practical application of the method, it was applied to measured magnetic anomaly data from Khalilabad area. For validity of the method, it was tested on a synthetic example with and without random noise. After adding 5%, 10% and 15% random noise to the synthetic data, the maximum error for the model parameters was seen to be less than ±3%. Moreover, it was found that the inversion results of magnetic data from an area in northeast Sirjan was in good agreement with the results from Euler deconvolution of the analytic signal of the magnetic data. Introduction: An important goal in the interpretation of magnetic anomaly data is to obtain the depth and the geometry or structural index of the causative source. To this end, a large number of methods exist to accomplish this goal. The analytic signal method is a popularly used method for this purpose. Using the analytic signal method, we can calculate both the depth and structural index of causative sources. However, the improved analytic signal method, presented in his paper, needs the computation of third-order derivatives of the magnetic anomaly and requires data of high precision or strict filtering. Methodology and Approaches: In this paper, we present an improved analytic signal method to interpret 2D magnetic anomaly data. The proposed method uses a combination of the analytic signal and its total gradient to estimate the depth and the structural index of the causative source. The feasibility of the proposed method to compute the source parameters is displayed on synthetic and measured magnetic anomalies. Results and Conclusions: We have proposed a new method to estimate the depth and the structural index of the causative source using the ratio of analytic signal to its total gradient. Our method provides two linear equations to estimate individually the depth and nature of a magnetic source. The feasibility of the new method is demonstrated on synthetic magnetic anomaly with and without random noise. For noise-free data, the structural index and the depth, estimated by the new method, are consistent with the theoretical values. For noise-corrupted data, our approach can provide reasonable results by applying upward continuation technique to lower the effect of noise. Application of the method on measured data indicates that the results of the method are in god agreement with the results computed by the Euler deconvolution of analytic signal method.
Language:
Persian
Published:
Journal Of Research on Applied Geophysics, Volume:4 Issue: 2, 2018
Pages:
351 to 363
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