實用大地電磁測勘法及其在臺灣之應用：儀器分析

作者:鄭懌(國立臺灣師範大學地球科學系)

摘要：

「大地電磁(Magnetotelluric)記錄系統為一套精密的電子儀器組合，可用來測量自然的地磁場強度變化及因之而感應出來的微弱地電流。系統中的磁力儀必須要能夠量出地磁場之X, Y, 和Z三分量，而測量地電流變化的電位計必須要有極高之輸入阻抗以避免電流分路而造成過大之誤差。在地電流量度上最重要的部分是要設計一組非極化之電極，並且要設法與地面接觸良好，以消除假性電位差。

《詳全文》

A Practical Magnetotelluric Method and Its Application in Taiwan: Instrumentation

Author: Yih Jeng(Department of Earth Sciences, National Taiwan Normal University)

Abstract：

The magnetotelluric recording instrument is a deliberately designed electronic system to record the natural magnetic fluctuations and the induced extremely weak terrestrial current. The magnetometer chosen must be capable of measuring the X, Y, and Z components of the mag-netic field. A high input impedance d.c. potentiometer is strongly recommended for sensing the electric field. The most important parts of the terrestrial current measurement are the non-polarizing electrodes which can eliminate the spurious potential created by the electrochemical polarization of the electrodes. Furthermore, the electrodes must be carefully coupled to the ground to avoid the instability of the measurement.
Another critical factor in a magnetotelluric survey is the selection of the energy passband. The data should be recorded at different sampling rates for varying sounding depths. A low-cut filtering of the data before A/D conversion may be employed to avoid the saturation of the converter before the high frequency signal can be registered.
The most troublesome problem in conducting magnetotelluric field work in Taiwan proba-bly comes from environmental factors like the dense population, high man-made noise, and pol-lution. However, the magnetotelluric data collected in this area may provide some interesting information which could qualitatively determine the types of environmental pollution.