The Telluric‐magnetotelluric Method

Hermance, John F.; Thayer, Richard E.

doi:10.1190/1.1440557

Cited by 35 publications

(22 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In general, however, one does not have 8 r ~ a b (27) and the approximate Equation (26) does not hold, although Hermance and Thayer (1975) have reported agreements within 10% between the correct [Z r] and the one inferred from the approximate relation (26) for a variety of sites in Iceland. The main point to be made, however, is that Equation (25) relates observations at distant sites.…”

Section: --1 D =mentioning

confidence: 82%

See 1 more Smart Citation

Magnetotelluric observational techniques on land

Fischer

1982

Geophysical Surveys

View full text Add to dashboard Cite

Abstract. During the period since the Workshops in Sopron and Murnau we have witnessed some quite remarkable changes in the techniques employed in magnetoteUurie (NIT) observations. These changes have brought about significant improvements in the quality of MT data that can be gathered today. The new techniques are very likely to bring improvements in many areas beside MT, but are reviewed here in the light of the progress they have rendered possible for MT soundings on land. Three main subjects are covered in this review. The first one is concerned with the use of cryogenic or SQUID magnetometers. The new instruments are presented to the geomagnetist. An explanation of how these instruments work is given without, however, details of their operation and fabrication, and without showing that they usually have a much larger, i.e. better, signal-to-noise ratio than conventional magnetometers. Next, the method of the remote magnetic reference is examined. Originally the MT method assumed incident signals in the form of plane waves. While it is known today that incident wave amplitudes which vary linearly with distance are perfectly acceptable for MT soundings, there are many other higher order distortions of the incident signal which are not acceptable. Most of these high order or local perturbations are man-made and can seriously falsify MT data. All processes of MT data analysis try to minimize the errors caused by locally perturbed signals. But they are only partly successful, especially when the perturbations produce strong cross-power bias. The remote magnetic reference method has proved far superior in avoiding most of this cross-power as well as faulty autopower. The last section of this review deals with the use in the field of microcomputers or microprocessors. These have made it possible to process the data on the site already to such a degree that the sounding crew knows whether the sounding is proceeding satisfactorily, and can decide how best to continue the survey work. Of particular interest is digital filtering, which is especially easy with the microcomputer, and which may be used to avoid specific sources of perturbation.

show abstract

Section: --1 D =mentioning

confidence: 82%

“…It is worth, at this point, mentioning a method somewhat related to that of the remote magnetic reference. This is the telluric-magnetotelluric method utilized by the Brown University group (Hermance and Thayer 1975;Hermance et al, 1976;Thayer et al, 1981). Here a complete MT base station is operated, as well as several remote or satellite …”

Section: --1 D =mentioning

confidence: 99%

Magnetotelluric observational techniques on land

Fischer

1982

Geophysical Surveys

View full text Add to dashboard Cite

show abstract

“…This method has been called the telluric-magnetotelluric method by Hermance and Thayer (1975). The authors calculated the magnetotelluric impedance tensor at the base station and in addition a telluric transfer tensor between the electric fields at the base statiorrand at the different field stations.…”

Section: Techniques With Natural Source Fieldsmentioning

confidence: 99%

Electromagnetic studies in geothermal regions

Berktold¹

1983

Geophysical Surveys

View full text Add to dashboard Cite

Abstract. During the past 25 yr, nearly all available electromagnetic and geoelectric techniques have been tested for their usefulness in geothermal exploration and exploitation. Dipole-dipole profiling, audiomagnetotellurics and controlled source electromagnetic methods are examples of those which have proven to be rather efficient for geothermal exploration. From the hundreds of field surveys which have been performed in many geothermal regions of the world, a large variety of geothermal regions and local geothermal systems, with different geological, hydrological and heat transfer characteristics, has been found to exist. Depending on the combination of these different characteristics each geothermal region or system presents a new problem which may need a different field technique or group of field techniques for optimal exploration. Despite these problems, new geothermal regions have been detected and structures and processes in geothermal systems are now much better understood. For example, advances have been made in the study of (a) the characteristics of porous/permeable hot water/vapor reservoirs and of fractioned zones for hot water/vapor circulation and production (b) the distribution and movement of cold meteoric and of hot water (c) the thermal insulation of reservoirs by cap-rocks (d) convective and/or conductive heat transfer and (e) the thermal influence of magma intrusions to high crustal levels.New exploration techniques, data analysis procedures and model calculations have been developed in the course of research in geothermal areas. They include the controlled source electromagnetic methods, the remote reference field technique and the development of better and faster algorithms for direct and inverse model calculations. Problems for the future are (a) the development and improvement of equipment and field techniques for more precise delineation and resolution of the conductivity distribution in geothermal areas especially those with productive zones of high porosity/permeability and fracturing, (b) the improvement of computerised data analysis in the field to optimise progress during the field measurements and (c) the development of more efficient interpretation procedures for the rather inhomogeneous conductivity distribution which exists in most geothermal areas.

show abstract

“…The main advantage of the T-MT method is that with one magnetic field measurement, almost the same information as contained in the impedance tensor Z (defined in Eq. 1) is obtained (Hermance and Thayer 1975).…”

Section: Introductionmentioning

confidence: 99%

“…In the mid-1970s, the telluric-magnetotelluric (T-MT) method was introduced (Hermance and Thayer 1975). In a T-MT survey, the magnetic field at a base site is related with the electric field at a field site according to…”

Section: Introductionmentioning

confidence: 99%

Introducing inter-site phase tensors to suppress galvanic distortion in the telluric method

et al. 2015

View full text Add to dashboard Cite

A common problem when interpreting magnetotelluric (MT) data is that they often are distorted by shallow unresolvable local structures, an effect known as galvanic distortion. We present two transfer functions that are (almost) resistant to galvanic distortion. First, we introduce the electric phase tensor, which is derived from the electric tensor, where the electric tensor relates the horizontal electric fields at a field and base site. The electric phase tensor is only affected by galvanic distortion, if present, at the base site. Second, we introduce the quasi-electric phase tensor, which is derived from the quasi-electric tensor, where the quasi-electric tensor relates the electric field at a field site with the magnetic field at a base site. The quasi-electric tensor is not affected by galvanic distortion. Using a synthetic data-set, we show that the sensitivity of the MT phase tensor, the quasi-electric phase tensor, and the electric phase tensor is comparable for our model under consideration. Furthermore, we demonstrate that stable (quasi-) electric phase tensors can be recovered from a real data-set with the use of existing processing software. In addition, we provide a formalism to propagate the uncertainties from the estimated (quasi-) electric and impedance tensors to their respective phase tensors. The uncertainties of the (quasi-) electric phase tensors are of the same order of magnitude as the uncertainties of the MT phase tensor. From our study, we conclude that the (quasi-) electric phase tensors are an attractive complement to the standard MT responses.

show abstract

The Telluric‐magnetotelluric Method

Cited by 35 publications

References 0 publications

Magnetotelluric observational techniques on land

Magnetotelluric observational techniques on land

Electromagnetic studies in geothermal regions

Introducing inter-site phase tensors to suppress galvanic distortion in the telluric method

Contact Info

Product

Resources

About