The Application Of Gravity Data In The Qiangtang Basin Structural Identification

The edge detection methods are widely used in geologic interpretation, and the method has a great development in recent years. Unfortunately, the real data acquired in the field do not exist without noise. The noise affects the processing and interpretation of the potential field data. In this thesis, we combine the wavelet denoising method and edge detection technology in the process of gravity data.Firstly, we evaluate and analyze the edge detection technology methods by using synthetic model and gravity data. Potential field edge detection method we used include the Tilt angle, the Theta Map, the total horizontal derivative of the Tilt angle, the curvature of gravity gradient tensor and normalized standard deviations. The Tilt angle and the Theta Map delineate synthetic model edge clearly, the results show that using the total horizontal derivative of the Tilt angle and the normalized standard deviations method is an effective tool for delineating edges of shallow and deep structures in the gravity data and is shown to behave robustly in the presence of noise. Based on these, we establish ETilt, ETheta and EThdr edge detection methods, the results show that these methods can detect more detail information.Secondly, we do some study of wavelet denoising of gravity data. The Fourier transform method is mostly used for suppressing the noise. The applications of Fourier transform are suitable for the stationary signals but not good for nonstationary signals. To address this difficulty, we propose a wavelet filtering to process gravity data. The method is based on the thresholding of the wavelet coefficients. We further illustrate the method by applying it to gravity data and removed the noise. Both synthetic and actual data show that the proposed method is an efficient and practical method.In a word, we have found that the edge detection methods and wavelet denoising technique have a good effect through the results of the model experiment and actual data processing. The major faults or tectonic boundary of Qiangtang Basin can be delineated with the methods mentioned above. These methods could provide more evidence and information for faults or tectonic boundary. Thus, we believe that the proposed methods has a great potential to be applied to the potential field data interpretion.