skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Improved workflow for 3D inverse modeling of magnetotelluric data: Examples from five geothermal systems

Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
Grant/Contract Number:
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Additional Journal Information:
Journal Volume: 53; Journal Issue: C; Related Information: CHORUS Timestamp: 2016-09-06 10:01:43; Journal ID: ISSN 0375-6505
Country of Publication:
United Kingdom

Citation Formats

Lindsey, Nathaniel J., and Newman, Gregory A.. Improved workflow for 3D inverse modeling of magnetotelluric data: Examples from five geothermal systems. United Kingdom: N. p., 2015. Web. doi:10.1016/j.geothermics.2014.09.004.
Lindsey, Nathaniel J., & Newman, Gregory A.. Improved workflow for 3D inverse modeling of magnetotelluric data: Examples from five geothermal systems. United Kingdom. doi:10.1016/j.geothermics.2014.09.004.
Lindsey, Nathaniel J., and Newman, Gregory A.. 2015. "Improved workflow for 3D inverse modeling of magnetotelluric data: Examples from five geothermal systems". United Kingdom. doi:10.1016/j.geothermics.2014.09.004.
title = {Improved workflow for 3D inverse modeling of magnetotelluric data: Examples from five geothermal systems},
author = {Lindsey, Nathaniel J. and Newman, Gregory A.},
abstractNote = {},
doi = {10.1016/j.geothermics.2014.09.004},
journal = {Geothermics},
number = C,
volume = 53,
place = {United Kingdom},
year = 2015,
month = 1

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.geothermics.2014.09.004

Citation Metrics:
Cited by: 7works
Citation information provided by
Web of Science

Save / Share:
  • Electromagnetic (EM) fields radiated from the transmission lines of the New Zealand electricity grid have been digitally recorded at test sites near the Tokaanu geothermal field. Amplitudes and phases of the 50 Hz signals (and the odd harmonics up to 450 Hz) were determined using a software implementation of a phase-locked filter. These data were then analyzed to determine the components of the magnetotelluric impedance tensor and the corresponding apparent resistivities and phases. At most sites, there was sufficient variation in the elliptical polarization of the EM fields to enable the impedance tensors to be determined in full. Sites wheremore » the EM data had been affected by near-source effects were identified by having large vertical magnetic field components and by being closer to a power line source than about 3--5 skin depths. With the test measurements, the north-eastern part of the Tokaanu geothermal field was successfully delineated giving low resistivities ({gt}5{Omega}m) on the inside and higher resistivities on the outside, in agreement with the Schlumberger array DC apparent resistivities. The small size of the 50 Hz magnetotelluric equipment and its portable nature make this method of resistivity measurement suitable for reconnaissance resistivity mapping in places with difficult access.« less
  • When measurements from a borehole are available, using such data to aid in the inversion of surface measurements may offer considerable benefits. This possibility has been recognized with regard to seismic data in exploration for hydrocarbons. In geothermal exploration, resistivity data from surface measurements and well logs may offer the best synergism. An example is given by using a resistivity log and magnetotelluric (MT) data from the East Mesa field.
  • This paper documents the numerical formulations, thermochemical data base, and possible applications of computer programs, SOLVGAS and GASWORKS, for calculating multicomponent chemical equilibria in gas-solid-liquid systems. SOLVGAS and GASWORKS compute simultaneous equilibria by solving simultaneously a set of mass balance and mass action equations written for all gas species and for all gas-solid or gas-liquid equilibria. The programs interface with a thermo-chemical data base, GASTHERM, which contains coefficients for retrieval of the equilibrium constants from 25[degrees] to 1200[degrees]C. The programs and data base model dynamic chemical processes in 30- to 40-component volcanic-gas systems. The authors can model gas evaporation frommore » magma, mixing of magmatic and hydrothermal gases, precipitation of minerals during pressure and temperature decrease, mixing of volcanic gas with air, and reaction of gases with wall rock. Examples are given of the gas-evaporation-from-magma and precipitation-with-cooling calculations for volcanic gases collected from Mt. St. Helens in September 1981. The authors predict: (1) the amounts of trace elements volatilized from shallow magma, deep magma, and wall rock, and (2) the solids that precipitate from the gas upon cooling. The predictions are tested by comparing them with the measured trace-element concentrations in gases and the observed sublimate sequence. This leads to the following conclusions: (1) most of the trace elements in the Mt. St. Helens gases are volatilized from shallow magma as simple chlorides; (2) some elements (for example, Al, Ca) exist dominantly in rock aerosols, not gases, in the gas stream; (3) near-surface cooling of the gases triggers precipitation of oxides, sulfides, halides, tungstates, and native elements; and (4) equilibrium cooling of the gases to 100[degrees]C causes most trace elements, except for Hg, Sb, and Se, to precipitate from the gas. 94 refs., 30 figs., 7 tabs.« less
  • Extremely broad emission wings at Hβ and Hα have been found in VLT-FLAMES Tarantula Survey data for five very luminous BA supergiants in or near 30 Doradus in the Large Magellanic Cloud. The profiles of both lines are extremely asymmetrical, which we have found to be caused by very broad diffuse interstellar bands (DIBs) in the longward wing of Hβ and the shortward wing of Hα. These DIBs are well known to interstellar but not to many stellar specialists, so that the asymmetries may be mistaken for intrinsic features. The broad emission wings are generally ascribed to electron scattering, althoughmore » we note difficulties for that interpretation in some objects. Such profiles are known in some Galactic hyper/supergiants and are also seen in both active and quiescent Luminous Blue Variables (LBVs). No prior or current LBV activity is known in these 30 Dor stars, although a generic relationship to LBVs is not excluded; subject to further observational and theoretical investigation, it is possible that these very luminous supergiants are approaching the LBV stage for the first time. Their locations in the HRD and presumed evolutionary tracks are consistent with that possibility. The available evidence for spectroscopic variations of these objects is reviewed, while recent photometric monitoring does not reveal variability. A search for circumstellar nebulae has been conducted, with an indeterminate result for one of them.« less