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A metrologic method of anomaly field amplitude bottom reduction in undersampled geomagnetic marine surveys
Language
English
Obiettivo Specifico
2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
Status
Published
JCR Journal
JCR Journal
Title of the book
Issue/vol(year)
2/22 (2001)
Pages (printed)
63-79
Issued date
2001
Last version
http://www.ingentaconnect.com/content/klu/mari/2001/00000022/00000002/00333504
Abstract
We show the results obtained by means of a seabed reduction technique on the intensity of geomagnetic anomaly fields applied to a synthetic case and then to the real case of a geomagnetic survey of eastern Ligurian Sea (Italy). The eastern Ligurian Sea has very intense short waves anomaly fields and a sea bed that varies greatly in depth. As a result the geomagnetic space signal is characterized by a very large spectral content; in these conditions it is not possible to obtain a full sampled marine survey and vertical continuation analytic procedures and standard numerical bottom reduction based on a single vertical incremental parameter, whichever is applicable, fails to give accurate results. The present technique, which has been fine-tuned over 4 years of experimentation in environmental researchs, aims to provide a simple and efficient means to reduce the distortion of geomagnetic anomalies field caused by the variation of distance between survey plane and magnetic outcrop source position. The compensation procedure is based on evaluation, by comparison of two measurements carried out at different altitudes, of the mean vertical increment typical of each anomaly field principal frequency component bands. The component anomaly fields are then corrected by application of the corresponding vertical increments and lastly, the anomaly geomagnetic field reduced to the sea-bed is computed as Inverse Fourier Transform of a spectrum built as synthesis of the component anomaly fields' spectra. The results obtained have shown a notable increase in definition of anomaly field intensity without the production of appreciable distortions or false geomagnetic echoes.
Sponsors
Hydrographic Institute of the Italian Navy,
References
Bozzo, E., Corrado, G., Elena, A., Faggioni, O. and Pinna, E., 1984,
Magnetic Anomalies and Deep Crustal Structure Along the Elba-
Levanto-Ottone-Varzi Line, Boll. Geof. Teor. Appl 26, 101–102,
67–75.
Cassano, E. and Maino, A., 1994, Carta Aeromagnetica d’Italia,
AGIP e Servizio Geologico Nazionale.
Chavez, R. E. and Garland, G. D., 1985, Linear inversion of gravity
data using the spectral expansion method, Geophys. 50(5), 820–
824.
Cooley, J.W. and Tukey, J. M., 1965, An Algorithm for theMachine
Calculation of Complex Fourier Series, Math. Compt. 91, 297–
301.
Cordell, L. and Grauch, V. J. S., 1985, Mapping basement magnetization
zones from aeromagnetic data in the San Juan basin, New
Mexico, in Hinze, W. J. (ed.), The utility of regional, gravity and
magnetic anomaly maps, Society of Exploration Geophysicist,
Tulsa, OK, pp. 181–197.
De Santis, A. and Meloni, A., 1991, Sulla Scelta del Campo
Geomagnetico di Riferimento in Italia, Istituto Nazionale di
Geofisica 6, 283–300.
Faggioni, O., Beverini, N. and Carmisciano, C., 1997, Geomagnetic
Time Variations and High Definition Study of Space Magnetic
Effects Induced by Artificial Submerged Sources, Boll. Geof.
Teor. Appl. 38(3–4), 211–228.
Faggioni, O., Beverini, N., Carmisciano, C. and Rossi, L., 1996,
Sulla Misura delle Variazioni Temporali del Campo Magnetico
79
Terrestre in Provincia della Spezia: Memorie Accademia Lunigianese
delle Scienze, Classe Scienze Matematiche, Fisiche e
Naturali 64–65, 161–184.
Faggioni, O., Pinna, E., Savelli, C. and Schreider, A., 1995, Geomagnetism
and Age Study of Tyrrhenian Seamounts: Geophys.
J. Int. 123, 915–930.
Faggioni, O., Palangio, P. and Pinna, E., 1991, Geomagnetic
Observatory of Terra Nova Bay Station –
Antarctica: Synthetic Reconstruction of Magnetogram
01.00(UTM)JD01.88:12.00(UTM)JD18.88: Atti Congr. Gr.
Naz. Geof. Terra Solida, Roma, 10, pp. 687–706.
Granser, H., 1987, Nonlinear inversion of gravity data using the
Schmidt-Lichtenstein approach, Geophys. 52 (1), 88–93.
Kanasewich, E. R., 1981, Time Sequence Analysis in Geophysics,
The University of Alberta Press.
Langel, R. A., 1987, International Geomagnetic Reference Field,
the sixth generation, J. Geomag. Geoelectr. 44, 679–707.
Leao, J. W. D, Menezes P. T. L., Beltrao, J. F. and Silva, J. B. C.,
1996, Gravity inversion of basement relief constrained by knowledge
of depth isolated points, Geophys. 61, (6), 1702–1714.
Leao J. W. D., Silva, J. B. C., 1989, Discrete linear transformations
of potential field data, Geophys. 54 (4), 497–507.
Naidu, P. S., 1970, Fourier transform of large scale aeromagnetic
field using a modified version of the Fast Fourier Transform,
Pure Appl Geophys 81, 17–25.
Phillips, J. D., 1996, Potential-field continuation: past practice
vs. modern methods, Proc. 66th Annual Meeting of Society of
Exploration Geophysicists, Denver, 1411–1414.
Pilkington, M. and Crossley, D. J., 1986, Determination of crustal
interface topography from potential fields, Geophys. 51 (6),
1277–1284.
Pilkington, M. and Urquhart, W. E. S., 1990, Reduction of potential
field data to a horizontal plane, Geophys. 55, (5), 549–555.
Thurston, J. B. and Smith, R. S., 1997, Automatic conversion of
magnetic data to depth, dip, and susceptibility contrast using the
SPI(TM) method, Geophys. 62 (3), 807–813.
Twigt,W., Slootweg, A. P. and Collette, B. J., 1979, Topography and
Magnetic Analysis of an Area Southeast of the Azores (36◦ N,
23◦ W), Mar. Geophys. Res. 4, 91–104.
United States Geological Survey, Potential Field Geophysical Software,
1992, USGS open file report, 92/18.
Xia, J., Sprowl, D. R., Adkins-Helijeson, D., 1993, Correction of
topographic distortions in potential-field data: a fast and accurate
approach, Geophys. 58 (4), 512–523.
Magnetic Anomalies and Deep Crustal Structure Along the Elba-
Levanto-Ottone-Varzi Line, Boll. Geof. Teor. Appl 26, 101–102,
67–75.
Cassano, E. and Maino, A., 1994, Carta Aeromagnetica d’Italia,
AGIP e Servizio Geologico Nazionale.
Chavez, R. E. and Garland, G. D., 1985, Linear inversion of gravity
data using the spectral expansion method, Geophys. 50(5), 820–
824.
Cooley, J.W. and Tukey, J. M., 1965, An Algorithm for theMachine
Calculation of Complex Fourier Series, Math. Compt. 91, 297–
301.
Cordell, L. and Grauch, V. J. S., 1985, Mapping basement magnetization
zones from aeromagnetic data in the San Juan basin, New
Mexico, in Hinze, W. J. (ed.), The utility of regional, gravity and
magnetic anomaly maps, Society of Exploration Geophysicist,
Tulsa, OK, pp. 181–197.
De Santis, A. and Meloni, A., 1991, Sulla Scelta del Campo
Geomagnetico di Riferimento in Italia, Istituto Nazionale di
Geofisica 6, 283–300.
Faggioni, O., Beverini, N. and Carmisciano, C., 1997, Geomagnetic
Time Variations and High Definition Study of Space Magnetic
Effects Induced by Artificial Submerged Sources, Boll. Geof.
Teor. Appl. 38(3–4), 211–228.
Faggioni, O., Beverini, N., Carmisciano, C. and Rossi, L., 1996,
Sulla Misura delle Variazioni Temporali del Campo Magnetico
79
Terrestre in Provincia della Spezia: Memorie Accademia Lunigianese
delle Scienze, Classe Scienze Matematiche, Fisiche e
Naturali 64–65, 161–184.
Faggioni, O., Pinna, E., Savelli, C. and Schreider, A., 1995, Geomagnetism
and Age Study of Tyrrhenian Seamounts: Geophys.
J. Int. 123, 915–930.
Faggioni, O., Palangio, P. and Pinna, E., 1991, Geomagnetic
Observatory of Terra Nova Bay Station –
Antarctica: Synthetic Reconstruction of Magnetogram
01.00(UTM)JD01.88:12.00(UTM)JD18.88: Atti Congr. Gr.
Naz. Geof. Terra Solida, Roma, 10, pp. 687–706.
Granser, H., 1987, Nonlinear inversion of gravity data using the
Schmidt-Lichtenstein approach, Geophys. 52 (1), 88–93.
Kanasewich, E. R., 1981, Time Sequence Analysis in Geophysics,
The University of Alberta Press.
Langel, R. A., 1987, International Geomagnetic Reference Field,
the sixth generation, J. Geomag. Geoelectr. 44, 679–707.
Leao, J. W. D, Menezes P. T. L., Beltrao, J. F. and Silva, J. B. C.,
1996, Gravity inversion of basement relief constrained by knowledge
of depth isolated points, Geophys. 61, (6), 1702–1714.
Leao J. W. D., Silva, J. B. C., 1989, Discrete linear transformations
of potential field data, Geophys. 54 (4), 497–507.
Naidu, P. S., 1970, Fourier transform of large scale aeromagnetic
field using a modified version of the Fast Fourier Transform,
Pure Appl Geophys 81, 17–25.
Phillips, J. D., 1996, Potential-field continuation: past practice
vs. modern methods, Proc. 66th Annual Meeting of Society of
Exploration Geophysicists, Denver, 1411–1414.
Pilkington, M. and Crossley, D. J., 1986, Determination of crustal
interface topography from potential fields, Geophys. 51 (6),
1277–1284.
Pilkington, M. and Urquhart, W. E. S., 1990, Reduction of potential
field data to a horizontal plane, Geophys. 55, (5), 549–555.
Thurston, J. B. and Smith, R. S., 1997, Automatic conversion of
magnetic data to depth, dip, and susceptibility contrast using the
SPI(TM) method, Geophys. 62 (3), 807–813.
Twigt,W., Slootweg, A. P. and Collette, B. J., 1979, Topography and
Magnetic Analysis of an Area Southeast of the Azores (36◦ N,
23◦ W), Mar. Geophys. Res. 4, 91–104.
United States Geological Survey, Potential Field Geophysical Software,
1992, USGS open file report, 92/18.
Xia, J., Sprowl, D. R., Adkins-Helijeson, D., 1993, Correction of
topographic distortions in potential-field data: a fast and accurate
approach, Geophys. 58 (4), 512–523.
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