MAGNETOTELLURICS WITH A REMOTE MAGNETIC REFERENCE

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Magnetotelluric measurements were performed simultaneously at two sites 4.8 km apart near Hollister, California. SQUID magnetometers were used to measure fluctuations in two orthogonal horizontal components of the magnetic field. The data obtained at each site were analyzed using the magnetic fields at the other site as a remote reference. In this technique, one mUltiplies the equations relating the Fourier components of the electric and magnetic fields by a component of magnetic field from the remote reference. By averaging the various crossproducts, one can obtain estimates of the impedance tensor that are unbiased by noise, provided there are no correlations ... continued below

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45 p.

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Gamble, Thomas D.; Goubau, Wolfgang M. & Clarke, John January 1, 1978.

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Magnetotelluric measurements were performed simultaneously at two sites 4.8 km apart near Hollister, California. SQUID magnetometers were used to measure fluctuations in two orthogonal horizontal components of the magnetic field. The data obtained at each site were analyzed using the magnetic fields at the other site as a remote reference. In this technique, one mUltiplies the equations relating the Fourier components of the electric and magnetic fields by a component of magnetic field from the remote reference. By averaging the various crossproducts, one can obtain estimates of the impedance tensor that are unbiased by noise, provided there are no correlations between the noises in the remote channels and the noises in the local channels. Even for data for which the E-E predicted coherencies were as low as 0.1, the apparent resistivities obtained from this technique were consistent with apparent resistivities calculated from high coherency data at adjacent periods. Apparent resistivities calculated by conventional analysis of the same data were biased by as much as two orders of magnitude. The estimated standard deviation for periods shorter than 3 s was less than 5%, and, for 87% of the data, was less than 2%. Where data bands overlapped between periods of 0.33 s and 1 s,the average discrepancy between the apparent resistivities was 1.8%.

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45 p.

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  • Journal Name: Geophysics

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  • Report No.: LBL-7032
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 1004896
  • Archival Resource Key: ark:/67531/metadc833072

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  • January 1, 1978

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  • May 19, 2016, 3:16 p.m.

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  • June 15, 2016, 8:55 p.m.

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Gamble, Thomas D.; Goubau, Wolfgang M. & Clarke, John. MAGNETOTELLURICS WITH A REMOTE MAGNETIC REFERENCE, article, January 1, 1978; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc833072/: accessed October 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.