长周期大地电磁测深数据采集及处理技术

Data acquisition and processing technology of long-period magnetotellurics

研究岩石圈底部的上地幔盖层甚至软流圈的电性结构,需要采集周期长达几万秒的长周期大地电磁场信号,这对仪器设备、采集以及处理技术都提出了更高的要求.本文论述了用于采集长周期信号的仪器设备及其特殊性,讨论了长周期大地电磁测深测站的布置要求,并采用长周期大地电磁测深仪器试采了长周期大地电磁场信号.对试采信号的处理结果表明,采用长周期仪器设备和稳定性好的不极化电极,合理布置测站,能够采集到最长周期达几万秒的长周期大地电磁场信号.

In order to research the electrical structure of the circle at the bottom of the upper mantle lid and the asthenosphere. It needs to acquire very long period Magnetotelluric （MT） signal, even as long as several tens of thousands of seconds. This requires some special characteristics and superior accuracy of MT instruments, and high technology of data processing. In this paper, we discussed some the special characteristics of long periods Magnetotellurie （LMT） instruments, especially the difference of magnetic sensor between broad band Magnetotellurie （BMT） and （LMT）. Then we summarized our experience for layout the LMT station, such as, increasing electrodes length to observe larger signal, used the long-time stable electrodes. And also we did some experiment on how to improve the accuracy of acquisition signal. The results of data processed show that if we applied very stable non-polarizing electrodes and set the station reasonably. We can get satisfactory signal as low frequency as we wanted.