1,721,166 research outputs found
A method to estimate the total magnetization direction from a distortion analysis of magnetic anomalies
No full textKnowledge of the declination and inclination of the total and induced magnetization vectors is normally required for the interpretation and analysis of magnetic anomalies. A new method of estimating the direction of the total magnetization vector of magnetized rocks from magnetic anomalies is proposed. The unknown declination and inclination (D*T and I*T) can be found by applying a reduction-to-the-pole operator to the measured anomalies for different couples of total magnetization direction parameters (DT and IT) and by observing the variation of the anomaly minimum as a function of both DT and IT. I*T and D*T are estimated using the maximum of this function. The method is applied to a real case and meaningful results are obtained; it is shown that the feasibility of the method is improved by removing the low-frequency components. -from Author
Anisotropic magnetic susceptibility in the continental lower crust and its implications for the shape of magnetic anomalies
No full textMagnetic anisotropy measurements on samples from the lower continental crust were made to test the hypothesis that anisotropy may cause deflection of the peak-to-trough axes of magnetic anomalies caused by mid- to lower crustal sources. Average anisotropy (P′) for these samples is 1.5 but can be as high as 3.4. Magnetic sources with P′ equal to the maximum determined in this study can cause azimuthal rotations of magnetic anomalies by up to about 25°, but P′ lower than or equal to 1.5 causes no significant rotation. Comparison of the model results to the abnormal shape of some magnetic anomalies in southern Italy indicate that these anomalies cannot be related easily to a strong and coherent AMS of the source rocks. The most probable explanation of such shapes is the existence of a strong remanent magnetization in subsequently rotated source bodies. -from Author
Interpretation of gravity and magnetic data in the Phlegraean Fields geothermal area, Naples, Italy.
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Interpretation of gravity and magnetic data in the Phlegraean Fields geothermal area, Naples, Italy.
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Crustal structure of the Ischia-Phlegrean geothermal fields, near Naples, Italy, from gravity and aeromagnetic data
No full textThe crustal structure and thermal regime of the Ischia-Phlegrean Fields volcanic area (Naples, Italy) have been intensively studied using gravity and aeromagnetic data. Analysis and interpretation of the data indicate that there often exists a complicated relation between density, magnetization and temperature. In particular, thermal effects, such as thermal demagnetization and thermal mineral alteration, may play an important role locally and could be the possible sources of the observed magnetic anomalies. Two interpretations are proposed. In the first the anomalies are related to compositional discontinuities in the intermediate-deep crust; in the second they are related to deep thermal sources, such as partially melted trachybasalts (gravity field) and a local rise of the Curie point surface (magnetic field). -from Author
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