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Probability distributions for magnetotellurics

Description: Estimates of the magnetotelluric transfer functions can be viewed as ratios of two complex random variables. It is assumed that the numerator and denominator are governed approximately by a joint complex normal distribution. Under this assumption, probability distributions are obtained for the magnitude, squared magnitude, logarithm of the squared magnitude, and the phase of the estimates. Normal approximations to the distributions are obtained by calculating mean values and variances from error propagation, and the distributions are plotted with their normal approximations for different percentage errors in the numerator and denominator of the estimates, ranging from 10% to 75%. The distribution of the phase is approximated well by a normal distribution for the range of errors considered, while the distribution of the logarithm of the squared magnitude is approximated by a normal distribution for a much larger range of errors than is the distribution of the squared magnitude. The distribution of the squared magnitude is most sensitive to the presence of noise in the denominator of the estimate, in which case the true distribution deviates significantly from normal behavior as the percentage errors exceed 10%. In contrast, the normal approximation to the distribution of the logarithm of the magnitude is useful for errors as large as 75%.
Date: November 1, 1982
Creator: Stodt, John A.
Partner: UNT Libraries Government Documents Department

Audio-magnetotelluric data collected in the area of Beatty, Nevada

Description: In the summer of 1997, electrical geophysical data was collected north of Beatty, Nevada. Audio-magnetotellurics (AMT) was the geophysical method used to collect 16 stations along two profiles. The purpose of this data collection was to determine the depth to the alluvial basement, based upon the needs of the geologists requesting the data.
Date: November 1, 1998
Creator: Williams, J.M.
Partner: UNT Libraries Government Documents Department

Controlled-source magnetotellurics: source effects

Description: In this paper we evaluate the CSMT impedance in the wavenumber domain, and compare the result with the full EM impedance obtained from the exact solution over the layered earth. Preliminary results show that we can find a pair of wavenumbers that reproduces the full EM impedance over the frequency range affected by source effects. This observation suggests that it is now possible to obtain the electrical resistivity using the low-frequency EM impedance data that can be represented by a pair of wavenumbers, thereby greatly simplifying the computational requirements. The process will involve a non-linear inversion of near-source impedance data for a pair of wavenumbers and a layered-earth resistivity structure.
Date: April 1, 1999
Creator: Smith, T. & Lee, K.H.
Partner: UNT Libraries Government Documents Department

MAPPING INDUCED POLARIZATION WITH NATURAL ELECTROMAGNETIC FIELDS FOR EXPLORATION AND RESOURCES CHARACTERIZATION BY THE MINING INDUSTRY

Description: In this quarter we completed the field test of the first two prototypes of the MT-24/LF. Two prototypes were deployed in Japan as land remote reference systems during a marine MT survey. The two systems acquired data continuously for about two weeks. Data processing is in progress. The IP Target Test Area has been selected. The complete survey will be conducted in Arizona Safford-Sol prospect owned by Kennecott. This is a large porphyry copper with a significant IP response. Finally the Acquisition software has been completed.
Date: October 20, 2001
Creator: Nichols, Edward
Partner: UNT Libraries Government Documents Department

Interpretation of Shallow Electrical Features From Electromagnetic and Magnetotelluric Surveys at Mount Hood, Oregon

Description: A magnetotelluric survey, with a reference magnetometer for noise cancellation, was conducted at accessible locations around Mount Hood, Oregon. Thirty-eight tensor magnetotelluric (MT) and remote telluric stations were set up in clusters around the volcano except for the northwest quadrant, a wilderness area. Because of limited access, station locations were restricted to elevations below 1829 m, or no closer than 5 km from the 3424-m summit. On the basis of the MT results, three areas were later investigated in more detail using a large-moment, controlled-source electromagnetic (EM) system developed at Lawrence Berkeley Laboratory and the University of California at Berkeley. One-dimensional interpretations of EM and MT data on the northeast flank of the mountain near the Cloud Cap eruptive center and on the south flank near Timberline Lodge show a similar subsurface resistivity pattern: a resistive surface layer 400-700 m thick, underlain by a conductive layer with variable thickness and resistivity of <20 ohm m. It is speculated that the surface layer consists of volcanics partially saturated with cold meteoric water. The underlying conductive zone is presumed to be volcanics saturated with water heated within the region of the central conduit and, possibly, at the Cloud Cap side vent. This hypothesis is supported by the existence of warm springs at the base of the mountain, most notably Swim Warm Springs on the south flank, and by several geothermal test wells, one of which penetrates the conductor south of Timberline Lodge. The MT data typically gave a shallower depth to the conductive zone than did the EM data. This is attributed, in part, to the error inherent in one-dimensional MT interpretations of geologically or topographically complex areas. On the other hand, MT was better for resolving the thickness of the conductive layer and deeper structure. The MT data show evidence for ...
Date: April 1, 1981
Creator: Wilt, M.; Goldstein, N.E. & Mozley, E.
Partner: UNT Libraries Government Documents Department

Final report [The 15th Workshop on Electromagnetic Induction in the Earth, held 8/20-26/2000, and The 5th Magnetotelluric Data Interpretation Workshop, 8/17-19/2000]

Description: This document reports on how the DOE helped to support travel of students and scientists to the conferences in Brazil. Attendee names, funding, and session titles are listed.
Date: June 25, 2002
Creator: Alumbaugh, David L.
Partner: UNT Libraries Government Documents Department

High Frequency Electromagnetic Impedance Imaging for Vadose Zone and Groundwater Characterization

Description: A geophysical experiment is described for characterizing the clastic dike systems, which are ubiquitous within the vadose zone at the Hanford Nuclear Reservation. because the dikes possess a significant electrical contrast from the insulating host medium, we have applied controlled source audio magnetotelluric (CSAMT) measurements to map their geometric extent and to further clarify if the dike complex acts as a conduit for contaminant transport within the vadose zone. Because of cost and weak natural field signal levels, we employed controlled field sourcing using the STRATGEM acquisition system. Use of artificial fields often goes with the assumption that the data required in the far-field of the transmitter.
Date: June 5, 2003
Creator: Newman, Greory A.; Alumbaugh, David L.; Hoversten, Michael & Nichols, Edward
Partner: UNT Libraries Government Documents Department

A Hydrostrat Model and Alternatives for Groundwater Flow and Contaminant Transport Model of Corrective Action Unit 99: Rainer Mesa-Shoshone Mountain, Nye County, Nevada

Description: The three-dimensional hydrostratigraphic framework model for the Rainier Mesa-Shoshone Mountain Corrective Action Unit was completed in Fiscal Year 2006. The model extends from eastern Pahute Mesa in the north to Mid Valley in the south and centers on the former nuclear testing areas at Rainier Mesa, Aqueduct Mesa, and Shoshone Mountain. The model area also includes an overlap with the existing Underground Test Area Corrective Action Unit models for Yucca Flat and Pahute Mesa. The model area is geologically diverse and includes un-extended yet highly deformed Paleozoic terrain and high volcanic mesas between the Yucca Flat extensional basin on the east and caldera complexes of the Southwestern Nevada Volcanic Field on the west. The area also includes a hydrologic divide between two groundwater sub-basins of the Death Valley regional flow system. A diverse set of geological and geophysical data collected over the past 50 years was used to develop a structural model and hydrostratigraphic system for the model area. Three deep characterization wells, a magnetotelluric survey, and reprocessed gravity data were acquired specifically for this modeling initiative. These data and associated interpretive products were integrated using EarthVision{reg_sign} software to develop the three-dimensional hydrostratigraphic framework model. Crucial steps in the model building process included establishing a fault model, developing a hydrostratigraphic scheme, compiling a drill-hole database, and constructing detailed geologic and hydrostratigraphic cross sections and subsurface maps. The more than 100 stratigraphic units in the model area were grouped into 43 hydrostratigraphic units based on each unit's propensity toward aquifer or aquitard characteristics. The authors organized the volcanic units in the model area into 35 hydrostratigraphic units that include 16 aquifers, 12 confining units, 2 composite units (a mixture of aquifer and confining units), and 5 intrusive confining units. The underlying pre-Tertiary rocks are divided into six hydrostratigraphic units, including three ...
Date: March 1, 2007
Creator: Group, NSTec Geotechnical Sciences
Partner: UNT Libraries Government Documents Department

Generalized Error Analysis for Conventional and Remote Reference Magnetotellurics

Description: An error analysis which applies to both conventional and remote reference magnetotelluric impedance and tipper estimates is developed based on the assumption that noise in the field measurements is governed by a complex normal distribution. Under the assumed model of noise it is shown that the theoretical expressions for the variances and covariances derived recently by Gamble et al (1979b) specifically for remote reference estimates apply to conventional estimates as well. However, calculations are biased if the impedance or tipper functions are biased. The impedance and tipper functions are calculated as ratios of two random functions of noisy field measurements. The expressions for the variances and covariances account for noise in both the numerator and denominator of the estimates. They are useful provided the probability that the magnitude of the random error in the denominator exceeds the magnitude of its expected value is small. Expressions for the bias errors of the impedance and tipper functions are obtained in order to assess the relative contributions of random and bias errors to the man squared error of the estimates. The relative magnitude of both random and bias errors depends on the noise level and on the values of the sample coherencies between various pairs of the field measurements used to compute a particular estimate.
Date: November 1, 1982
Creator: Stodt, John A.
Partner: UNT Libraries Government Documents Department

THE HOHI GEOTHERMAL AREA, KYUSHU, JAPAN

Description: Geophysical data from surface measurements and downhole pressure/temperature data in northern Kyushu centered around Mount Waita are examined. The study area includes the geothermal fields supplying steam for the Hatchobaru and Ohtake power stations, but also extends a considerable distance to the northwest. Evidence from drilling logs, magnetotelluric surveys, lost-circulation horizons, downhole temperature surveys, and thermal and chemical properties of surface hot-spring discharge suggests the presence of a large geothermal reservoir north of the towns of Takenoyu and Hagenoyu.
Date: January 22, 1985
Creator: Pritchett, J.W.; Garg, S.K.; Farrell, W.E.; Ishido, T.; Yoshimurs, T.; Murakami, K. et al.
Partner: UNT Libraries Government Documents Department

Magnetotelluric Responces of Three-Dimentional Bodies in Layered Earths

Description: The electric and magnetic fields scattered by a three-dimensional inhomogeneity in a conducting earth result largely from current-gathering, a boundary polarization charge phenomenon that becomes increasingly important as frequency falls. Boundary charges cause normalized electric field magnitudes, and thus tensor apparent resistivities and magnitudes of vertical admittance elements, to remain anomalous as frequency approaches zero. However, these E-field distortions below certain frequencies are essentially in-phase with the incident electric field. In addition, secondary magnetic field amplitudes over a body ultimately decline in proportion to the layered host impedance. It follows that tipper element magnitudes and all MT function phases become minimally affected at low frequencies by an inhomogeneity. Resistivity structure in nature is a collection of inhomogeneities of various scales, and the small structures in this collection can have MT responses as strong as those of the large structures. Hence, a severe distortion due to current-gathering in any nearby, small-scale geological noise can be superimposed to arbitrarily low frequencies upon the apparent resistivities and vertical admittance magnitudes of buried targets. On the other hand, the MT responses of small and large bodies have frequency dependencies that are, in general, separated as the square of the geometric scale factor distinguishing the different bodies.
Date: November 1, 1982
Creator: Wannamaker, Phillip E.; Ward, Stanley H. & Hohmann, Gerald W.
Partner: UNT Libraries Government Documents Department

Weighted Least Squares Estimates of the Magnetotelluric Transfer Functions from Nonstationary Data

Description: Magnetotelluric field measurements can generally be viewed as sums of signal and additive random noise components. The standard unweighted least squares estimates of the impedance and tipper functions which are usually calculated from noisy data are not optimal when the measured fields are nonstationary. The nonstationary behavior of the signals and noises should be exploited by weighting the data appropriately to reduce errors in the estimates of the impedances and tippers. Insight into the effects of noise on the estimates is gained by careful development of a statistical model, within a linear system framework, which allows for nonstationary behavior of both the signal and noise components of the measured fields. The signal components are, by definition, linearly related to each other by the impedance and tipper functions. It is therefore appropriate to treat them as deterministic parameters, rather than as random variables, when analyzing the effects of noise on the calculated impedances and tippers. From this viewpoint, weighted least squares procedures are developed to reduce the errors in impedances and tippers which are calculated from nonstationary data.
Date: November 1, 1982
Creator: Stodt, John A.
Partner: UNT Libraries Government Documents Department

Intersections, ideals, and inversion

Description: Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly onedimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons.
Date: October 1, 1998
Creator: Vasco, D.W.
Partner: UNT Libraries Government Documents Department

Major results of geophysical investigations at Yucca Mountain and vicinity, southern Nevada

Description: In the consideration of Yucca Mountain as a possible site for storing high level nuclear waste, a number of geologic concerns have been suggested for study by the National Academy of Sciences which include: (1) natural geologic and geochemical barriers, (2) possible future fluctuations in the water table that might flood a mined underground repository, (3) tectonic stability, and (4) considerations of shaking such as might be caused by nearby earthquakes or possible volcanic eruptions. This volume represents the third part of an overall plan of geophysical investigation of Yucca Mountain, preceded by the Site Characterization Plan (SCP; dated 1988) and the report referred to as the Geophysical White Paper, Phase 1, entitled Status of Data, Major Results, and Plans for Geophysical Activities, Yucca Mountain Project (Oliver and others, 1990). The SCP necessarily contained uncertainty about applicability and accuracy of methods then untried in the Yucca Mountain volcano-tectonic setting, and the White Paper, Phase 1, focused on summarization of survey coverage, data quality, and applicability of results. For the most part, it did not present data or interpretation. The important distinction of the current volume lies in presentation of data, results, and interpretations of selected geophysical methods used in characterization activities at Yucca Mountain. Chapters are included on the following: gravity investigations; magnetic investigations; regional magnetotelluric investigations; seismic refraction investigations; seismic reflection investigations; teleseismic investigations; regional thermal setting; stress measurements; and integration of methods and conclusions. 8 refs., 60 figs., 2 tabs.
Date: December 31, 1995
Creator: Oliver, H.W.; Ponce, D.A. & Hunter, W.C.
Partner: UNT Libraries Government Documents Department

Multistation magnetotellurics. Final report, 1 January 1996--30 June 1997

Description: The author has developed the foundations of a practical multivariate approach to processing magnetotelluric array data. Compared to current standards for magnetotelluric data processing, the multivariate approach is unique in that all available data channels are used simultaneously. The approach is outlined in this report. Using Multmtrn, a program for multiple station analysis of magnetotelluric data, the author achieved significant improvements in apparent resistivity and phase estimates in initial tests. Examples of the use of this approach are given including: Carrizo Plain and Parkfield electromagnetic profiling data; sea floor magnetotelluric (MT) data from the Gulf of Mexico; MT survey in a culturally noisy area of Bavaria; and Parkfield/Hollister earthquake monitoring array data. Experience with these projects has resulted in an improved program. The new version of the code is available at http://www.cg.NRCan.gc.ca/mtnet/mtnet.html or by contacting egbert{at}oce.orst.edu. Appendices of this report present documentation for Multmtrn.
Date: 1997-23~
Creator: Egbert, G. D.
Partner: UNT Libraries Government Documents Department

Tectonic Versus Volcanic Origin of the Summit Depression at Medicine Lake Volcano, California

Description: Medicine Lake Volcano is a Quaternary shield volcano located in a tectonically complex and active zone at the transition between the Basin and Range Province and the Cascade Range of the Pacific Province. The volcano is topped by a 7x12 km elliptical depression surrounded by a discontinuous constructional ring of basaltic to rhyolitic lava flows. This thesis explores the possibility that the depression may have formed due to regional extension (rift basin) or dextral shear (pull-apart basin) rather than through caldera collapse and examines the relationship between regional tectonics and localized volcanism. Existing data consisting of temperature and magnetotelluric surveys, alteration mineral studies, and core logging were compiled and supplemented with additional core logging, field observations, and fault striae studies in paleomagnetically oriented core samples. These results were then synthesized with regional fault data from existing maps and databases. Faulting patterns near the caldera, extension directions derived from fault striae P and T axes, and three-dimensional temperature and alteration mineral models are consistent with slip across arcuate ring faults related to magma chamber deflation during flank eruptions and/or a pyroclastic eruption at about 180 ka. These results are not consistent with a rift or pull-apart basin. Limited subsidence can be attributed to the relatively small volume of ash-flow tuff released by the only known major pyroclastic eruption and is inconsistent with the observed topographic relief. The additional relief can be explained by constructional volcanism. Striae from unoriented and oriented core, augmented by striae measurements in outcrop suggest that Walker Lane dextral shear, which can be reasonably projected from the southeast, has probably propagated into the Medicine Lake area. Most volcanic vents across Medicine Lake Volcano strike north-south, suggesting they are controlled by crustal weakness related to Basin and Range extension. Interaction of dextral shear, Basin and Range extension, and the ...
Date: May 1, 2010
Creator: Gwynn, Mark Leon
Partner: UNT Libraries Government Documents Department

New approaches to estimation of magnetotelluric parameters. Final technical report, 1 August 1989--31 July 1991

Description: Fully efficient robust data processing procedures were developed and tested for single station and remote reference magnetotelluric (Mr) data. Substantial progress was made on development, testing and comparison of optimal procedures for single station data. A principal finding of this phase of the research was that the simplest robust procedures can be more heavily biased by noise in the (input) magnetic fields, than standard least squares estimates. To deal with this difficulty we developed a robust processing scheme which combined the regression M-estimate with coherence presorting. This hybrid approach greatly improves impedance estimates, particularly in the low signal-to-noise conditions often encountered in the ``dead band`` (0.1--0.0 hz). The methods, and the results of comparisons of various single station estimators are described in detail. Progress was made on developing methods for estimating static distortion parameters, and for testing hypotheses about the underlying dimensionality of the geological section.
Date: December 31, 1991
Creator: Egbert, G. D.
Partner: UNT Libraries Government Documents Department

Bias removal for conventional magnetotelluric data

Description: An algorithm has been developed for the removal of autopower bias errors from conventional magnetotelluric (MT) data. Nonlinear equations involving autopowers as unknowns with crosspower coefficients are obtained by cross substitutions between the eight referenced impedance equations to eliminate the four impedances. Although exact solutions to the nonlinear equations can be computed, they are often sensitive to noise components in the crosspower coefficients, due to degeneracy of the equations as Z/sub xx/ and Z/sub yy/ approach zero or as the coherence between the magnetic field components H/sub x/ and H/sub y/ approaches unity. However, the ordinary coherence functions between various pairs of the horizontal field components provide additional information. This information is incorporated as constraints by developing a constrained iterative solution for the autopowers. The solution is outlined and its usefulness is explored with examples of its application to field data.
Date: September 1, 1983
Creator: Stodt, J. A.
Partner: UNT Libraries Government Documents Department

Two and Three Dimensional Magnetotelluric Inversion. Final Report

Description: Electrical conductivity depends on properties such as the presence of ionic fluids in interconnected pores that are difficult to sense with other remote sensing techniques. Thus improved imaging of underground electrical structure has wide practical importance in exploring for groundwater, mineral and geothermal resources, and in assessing the diffusion of fluids in oil fields and waste sites. Because the electromagnetic inverse problem is fundamentally multi-dimensional, most imaging algorithms saturate available computer power long before they can deal with the complete data set. We have developed an algorithm to directly invert large multi-dimensional data sets that is orders of magnitude faster than competing methods. We have proven that a two-dimensional (2D) version of the algorithm is highly effective for real data and have made substantial progress towards a three-dimensional (3D) version. We are proposing to cure identified shortcomings and substantially expand the utility of the existing 2D program, overcome identified difficulties with extending our method to three-dimensions (3D) and embark on an investigation of related EM imaging techniques which may have the potential for even further increasing resolution.
Date: May 1, 1993
Creator: Booker, John
Partner: UNT Libraries Government Documents Department

Analysis of deep seismic reflection and other data from the southern Washington Cascades. Task No. 2, Quarterly report, [March 1, 1993--May 31, 1993]

Description: This report covers the period from March 1, 1993 to May 31, 1993. The overall goals of the program task are to provide a final synthesis of six deep seismic reflection profiles and other geological and geophysical data from the southern Washington Cascades region where a probable extensive deep sedimentary basin has been discovered. This deep sedimentary basin is hypothesized from geological, regional magnetotelluric (MT), gravity, magnetic, and seismic reflection data as described in the American Association of Petroleum Geologists (AAPG) article by Stanley and others (1992). This report analyzed three seismic reflection profiles acquired by the Morgantown Energy Technology Centers in combination with the extensive MT and other data to outline a probable geological model for a thick conductive section of rocks in the southern Washington Cascades (called the Southern Washington Cascades conductor, SWCC). Earlier MT models suggested that the section consisted of an east-dipping package that extended to depths of as much as 20 km but appeared to surface in the Bear Canyon area near Morton, Washington and along the axis of the Carbon River and Morton anticlines. Interpretation of the first three DOE seismic reflection approximately confirmed the MT interpretation and added new information on anticlinal structures and detailed stratigraphy. In this quarterly report, we summarize the progress over the first two quarters of the program for FY93, and project the possible findings during the remainder of the project.
Date: February 1, 1994
Creator: Stanley, W. D.
Partner: UNT Libraries Government Documents Department

Geologic research of conventional and unconventional hydrocarbon resources. Quarterly report, October 1, 1992--March 1, 1993

Description: This report covers the period from October 1, 1992 to March 1, 1993. The overall goals of the program task are to provide a final synthesis of six deep seismic reflection profiles and other geological and geophysical data from the southern Washington Cascades region where a probable extensive deep sedimentary basin has been discovered. This deep sedimentary basin is hypothesized from geological, regional magnetotelluric (MT), gravity, magnetic , and seismic reflection data as described in the American Association of Petroleum Geologists (AAPG) article by Stanley and others (1992). This report analyzed three seismic reflection profiles acquired by the Morgantown Energy Technology Centers in combination with the extensive MT and other data to outline a probable geological model for a thick conductive section of rocks in the southern Washington Cascades (called the Southern Washington Cascades conductor, SWCC). Earlier MT models suggested that the section consisted of an east-dipping package that extended to depths of as much as 20 km but appeared to surface in the Bear Canyon area near Morton, Washington and along the axis of the Carbon River and Morton anticlines. Interpretation of the first three DOE seismic reflection approximately confirmed the MT interpretation and added new information on anticlinal structures and detailed stratigraphy. In this quarterly report, we summarize the progress over the first two quarters of the program for FY93, and project the possible findings during the remainder of the project. A milestone chart for the first two quarters has been submitted separately, along with cost reports, but a copy of these items are attached for completeness.
Date: March 2, 1993
Partner: UNT Libraries Government Documents Department

A Geological and Geophysical Study of the Baca Geothermal Field, Valles Caldera, New Mexico

Description: The Baca location {number_sign}1 geothermal field is located in north-central New Mexico within the western half of the Plio-Pleistocene valles Caldera. Steam and hot water are produced primarily from the northeast-trending Redondo Creek graben, where downhole temperatures exceed 500 F. Stratigraphically the reservoir region can be described as a five-layer sequence that includes (1) caldera fill and the upper units of the Bandelier ash flow tuff, (2) the lower members of this tuff, which comprise the main reservoir rock at Baca, (3) the Pliocene Paliza Canyon volcanics, (4) Tertiary sands and Paleozoic sedimentary rocks, and (5) Precambrian granitic basement. Production is controlled by fractures and faults that are ultimately related to activity in the Rio Grande Rift system. Geophysically, the caldera is characterized by a gravity minimum and a resistivity low. A 40-mgal gravity minimum over the caldera is due mostly to the relatively low-density volcanics and sediments that fill the caldera and probably bears no relation to deep-seated magmatic sources. Two-dimensional gravity modeling indicates that the depth to Precambrian basement in Redondo Canyon is probably at least 3 km and may exceed 5 km in eastern parts of the caldera. Telluric and magnetotelluric surveys have shown that the reservoir region is associated with low resistivity and that a deep low-resistivity zone correlates well with the depth of the primary reservoir inferred from well data.
Date: March 1, 1982
Creator: Wilt, M. & Haar, S.V.
Partner: UNT Libraries Government Documents Department

Application of natural electromagnetic field methods (magnetotellurics/geomagnetic variations) to exploring for energy resources: development of a broad-band data acquisition/processing facility. Topical report, May 1, 1979-April 30, 1980

Description: Progress is summarized in the following fields: a review of the present state of knowledge of the deep thermal regimes associated with major rift systems of the world, field studies of several major tectonomagmatic systems, and design and testing of new magnetotelluric/geomagnetic variation field system for studying thermal regimes in the continental crust. (MHR)
Date: January 1, 1980
Creator: Hermance, J.F.
Partner: UNT Libraries Government Documents Department