航磁异常深部弱信号提取技术研究

Extracting Weak Magnetic Signals at Depth from Aeromagnetic Anomaly Data

磁异常通常是地下不同深度磁性地质体产生磁场的叠加,在规范高度的航磁测量结果中,深部磁性体所产生的异常通常表现为弱而平缓,其水平与垂向分辨率均较低,在航磁资料处理解释中难以有效捕获。因此,应用适当方法提取由深部地质体引起的弱磁信息是十分必要的。本文采用精度高且稳定的位场延拓技术将航磁异常向下延拓,可以稳定增强磁异常幅度,随着延拓面与场源之间距离的减小,浅成磁信号与深成磁信号的视深度差异将增大,在对数功率谱上可以将其区分,而后可利用匹配滤波方法将浅部信号剥离,从而得到深部弱信号,同时可计算深部弱信号的视深度。

Magnetic anomalies are superposition of magnetic fieht anomalies of geological bodies at different depths in the subsurface. In aeromagneli surveys, such signals from depth are generally weak and gentle, with low resolutions in both horizontal and vertical direetions. Thus they are difficuh to extraet from aeromagnetic data processed aud interpreted. To solve this problem, this work uses the high-precisiun and stable downward continuation method to enhance amplitudes of magnetic anomalies. With decreasing distances between the continuation plane and field source, the apparent depth diffrence between shallow and deep magnetic signals increases progressively. So they can be distinguished on the logarithm power spectrum. Then the shallow signals are removed by the matched filter to isolate the deep signals. Meanwhile the apparent depths of these deep signals can be calculated.