PRC_MTMV和EMTF在长周期大地电磁数据处理中的应用

The application of PRC_MTMV and EMTF in long-period magnetotelluric data processing

长周期大地电磁信号强度弱,频带宽,容易受到多种噪声的干扰,观测数据不满足加性、平稳和最小相位特性.因而,其数据处理仍有较多难点.常规的大地电磁数据处理方法是相似的,其主要差别是在时域或频域压制噪声、提高信噪比的数学方程和算法不同.为了提高数据处理的可靠性,拓宽方法的选择范围,本文介绍了广泛使用的PRC_MTMV和较少使用的EMTF两套软件系统的处理原理、参数配置以及用于处理长周期大地电磁资料的基本流程.利用两套系统对实测数据进行处理,对比发现,PRC_MTMV处理得到的视电阻率和相位曲线总是比EMTF的曲线平滑;EMTF的远参考处理对视电阻率曲线高频部分有较大的改善,说明EMTF能够有效克服磁场干扰;将同一测点长周期和宽频测深曲线拼接,二者的效果是相当的,表明EMTF能够满足需要并用于处理长周期大地电磁数据.

Long-period magnetotelluric signals can usually be contaminated by kinds of noises for the features of being weak and having a broad band, which makes the field data biased badly and deviate the hypothesis of being additive, stationary and minimum-phase required by the traditional data processing methods. As a result, many problems still lie in long-period magnetotelluric data processing. General steps of common data processing methods are the same. The differences among various methods mainly lie in kinds of techniques used to suppress noises and improve the signabnoise ratio, such as different mathematical formulas and algorithms. At present, softwares for long period magnetotelluric data processing are few and quite immature. In order to improve the reliability of data processing by using different softwares and expand the range of optional methods, in this paper, we give a muchdetailed introduction about the principles, parameter configurations and processing techniques of two magnetotelluric data processing systems, which are called by PRC_MTMV and EMTF, and their application to long-period magnetotelluric data processing. By processing practical field data using the two systems and comparing the resulting apparent resistivity and impedance phase curves, we find that the curves of PRC_MTMV are always smoother than that of EMTF, and even stay stable during some bands. However, curves from remote reference of EMTF can be greatly improved at high frequency band, which proves that EMTF is capable of getting rid of magnetic noise. By combining with broad-band sounding curves, combined curves of both systems are comparable, which shows EMTF are effective and can be used for long-period magnetoteiluric data processing.