| dc.description.abstract | Magnetic and gravity data are generally used to discuss geological structure characteristics, and the most applications are used to determine the location of the sources. Among the interpretation techniques, the methods of the analytic signal and Euler deconvolution have been widely adopted for these purposes. The major advantage of using these two techniques is that the determination of magnetic source locations and depths is independent of the ambient earth magnetic parameters. In this thesis, generally based on the analytic signal and Euler deconvolution we attempt to develop new methods and then discuss its applications.
We have developed a new method by using the joint analysis of analytic signal and Euler deconvolution to estimate the parameters of 2D magnetic sources, especially to identify the horizontal locations, depths, structural types (indices), magnetization contrasts and structural dips. Furthermore, this method is used to estimate the possible magnetization contrast of geomagnetic reversals. This information could be a useful constrain for geomagnetic age modeling. Thus, one does not need to assume a constant magnetization of the magnetized layer in the modeling. This could make the synthetic magnetic anomaly more realistic. This method has been tested to determine the magnetization contrast of the Brunhes-Matuyama boundary of geomagnetic reversal.
The Poisson theorem provides a simple relationship between the gravity and magnetic potentials. Based on the simple Poisson theorem, magnetization/density ratio (MDR) can be estimated. Here, we combined the Poisson theorem and analytic signal technique to estimate MDR. Follow this method the MDR values can be determined from gravity and magnetic data. Apply this method to a profile across the offshore area of the northern Taiwan. In comparison with the reflection seismic profile, it shows that the method can help us to identify the existence of a deep-seated igneous body beneath the area of Mienhuayu and Pengchiagu islands off northern Taiwan.
Finally, we show a magnetic survey result for the purpose of detecting buried buildings of Siaolin Village in southern Taiwan after the catastrophic landslide induced by Typhoon Morakot in 2009. Compared the original locations of buildings with the magnetic data analysis results, high-resolution magnetic survey can effectively identify positions of buried buildings in Siaolin Village. The estimated depths of the possible buried buildings are about 5-10 meters deep. In addition, magnetic data analysis can further suggest the possible debris-flow direction of N250o, because the northern part of village was mostly destroyed off while the southern part of village buildings remained in place.
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