Electromagnetic methods in applied geophysics
Electromagnetic methods in applied geophysics
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DOI：
10.1007/bf01452955
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发表时间：
1980-09
期刊：
影响因子：
--
通讯作者：
K. Vozoff
中科院分区：
文献类型：
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作者：
K. Vozoff
近年来，除了传统的矿物领域外，地热能、煤炭和永久冻土的重要性日益增加，也影响了应用电磁学的研究。对煤和冰等近绝缘体的兴趣促进了雷达和其他VHF-UHF技术的发展。解释这些测量结果需要这些材料在6-10个十年频率范围内的可靠物理特性数据。通过使用瞬态数据采集技术和类似于反射地震学中使用的数据处理方案，提高了高频场数据的效用。在应用电磁物理学的更常见的频率范围（30 Hz-3 kHz）内的主要发展也涉及瞬变。在某些情况下，它们似乎具有用离散频率法不易获得的基本灵敏度。三维问题的计算机模拟进展缓慢。改进的二维反演程序正在使用中，但它们的能力非常有限。超导性在几种新仪器的开发中发挥了作用。SQUID和SQUID梯度仪自上次研讨会以来有了很大改进。噪声级为的坚固的SQUID磁力计现在可以在商业上获得。相应地，温度计的灵敏度也得到了提高。一个直径3米的超导环将于1979年初试飞，这是一个新的低频系统的原型，用于从直升机上绘制电导率。由于低频和预期的低系统噪声，预计它在导电地层中的穿透深度比现有最好的系统更大。一种新的大地电磁法程序，使用远场参考，将视电阻率和其他响应函数的散射降低到百分之几。如果我们要从这一发展中受益，现在必须在建模和解释MT结果方面做出进一步的改进。
Applied electromagnetic research in recent years has been influenced by the growing importance of geothermal energy, coal, and permafrost, in addition to the traditional area of minerals. The interest in near-insulators such as coal and ice encouraged development of radars and other VHF-UHF techniques. Interpreting such measurements required reliable physical properties data for those materials over a frequency range of 6–10 decades. The utility of the high frequency field data has been improved through the use of transient techniques for data acquisition, and data processing schemes similar to those used in reflection seismology. The major developments in the more usual frequency range of applied geophysics (30 Hz—3 kHz) have also dealt with transients. In certain circumstances they appear to have a fundamental sensitivity not readily obtained by discrete frequency methods.Computer modelling of 3-D problems is progressing slowly. Improved 2-D inversion programs are in use, but their capabilities are very limited.Superconductivity plays a role in several new instrument developments. SQUIDs, and SQUID gradiometers have improved considerably since the last Workshop. Robust SQUID magnetometers having noise levels ofcan now be obtained commercially. Gradiometer sensitivities have improved accordingly. A superconducting loop 3 metres in diameter, to be test flown early in 1979, is the prototype of a new low frequency system to map conductivity from a helicopter. It is expected to have greater depth penetration in conductive terranes than the best existing systems, because of the low frequency and anticipated low system noise.A new magnetotelluric procedure, using a remote field reference, reduced the scatter in apparent resistivities and other response functions to a few percent. Further improvements must now be made in modelling and interpreting MT results if we are to benefit from this development.