Horizontal Derivative Iteration Method for Downward Continuation of Gravity and Magnetic Data
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摘要: 向下延拓是重磁数据处理的常用手段，能有效地区分叠加异常、增强浅部异常，但现有向下延拓算法的计算大多是不稳定的，且易受噪声的干扰，往往造成异常形态的畸变.提出一种基于水平导数和向上延拓联合迭代的向下延拓算法，由于向上延拓和水平导数的计算是稳定的，因此该向下延拓方法可有效地增强结果的准确性和稳定性.理论模型试验表明该方法的向下延拓结果比Fourier变换计算结果更加稳定、准确，且受噪音干扰小.将该方法应用于实际数据的处理，结果显示该方法能稳定和准确地完成异常的向下延拓任务，且有效地增强了浅部局部异常.Abstract: Downward continuation is an effective tool in the processing of potential field data, which can identify overlap anomalies and enhance weak anomalies effectively. But the existing computation methods of downward continuation easily distort the true feature of potential field data since they are unstable and sensitive to noise. In this paper, we present an iteration method based on horizontal derivative, and we prove that downward continuation can be computed by the combination of upward continuation and horizontal derivative, and the computation of upward continuation and horizontal derivative is stable, which confirms stability and reliability of the method. The proposed method has been tested on synthetic potential field data, and it is found that the output results are more stable and accurate than those computed by the Fourier transform, and more insensitive to noise. Its application to real potential field data shows the same results and it really enhances the local anomalies.
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Key words:
- gravity and magnetic /
- horizontal derivative /
- downward continuation /
- iteration /
- geophysics
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图 1 模型重力异常不同延拓方法应用效果
a.球体埋深为15 m时引起的重力异常；b.球体埋深为12 m时的异常；c.利用本文方法将1a中异常向下延拓3 m；d.利用Fourier变换将1a中异常向下延拓3 m；e.球体埋深为10 m时异常；f.利用本文方法将1a中异常向下延拓5 m；g.利用Fourier变换将1a中异常向下延拓5 m；h.图 1e和1g异常的差；i.图 1e和1h异常的差
Fig. 1. The application effect of different downward continuation methods of synthetic gravity anomaly
图 2 剖面重力异常不同延拓方法应用效果
a.不同方法向下延拓3 m后异常；b.不同方法向下延拓5 m后异常
Fig. 2. The application effect of different downward continuation methods of profile gravity anomaly
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