Abstract
A comparison between ground level total magnetic field intensity anomaly map (F) of Italy and the total intensity aeromagnetic map by ENI/AGIP, had shown that an anomaly pattern for the Albegna basin (South Tuscany), quite evident from ground measurements, doesn’t show in the aeromagnetic map. Ligurian units, made of ophiolite blocks (metagabbros, basalts, serpentinites), intrusives and subordinate volcanic products, all able to trigger a strong magnetic signal, could not be excluded in the area, and for this reason the magnetic anomaly estimated by ground level measurements was not considered unreasonable. In this paper the result of a magnetic survey finalized to verify the authentic existence of such a large magnetic total intensity anomaly in the Albegna basin, is reported. On the basis of the new result, the suspected ground level total intensity anomaly in the Albegna basin, was demonstrated to be non-existent and then the Italian Magnetic Database corrected accordingly. Measurements and procedures that brought to the magnetic elements elaboration and new anomaly maps for Albegna basin, are shown here. Normal 0 14 false false false IT X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabella normale"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}
Highlights
A comparison between ground level total magnetic field intensity anomaly map (F) of Italy and the total intensity aeromagnetic map by ENI/AGIP, had shown that an anomaly pattern for the Albegna basin (South Tuscany), quite evident from ground measurements, doesn’t show in the aeromagnetic map
In Italy ground level magnetic measurements on the second order network were performed in an organized national effort only once between 1977 and 1981, within the framework of the Progetto Finalizzato Geodinamica of the Consiglio Nazionale delle Ricerche (PFG-CNR)
A strong magnetic anomaly circularly shaped that can be seen in the ground level map, does not show in the aeromagnetic map
Summary
Magnetic field measurements are undertaken in different ways and for different reasons. For their institutional roles, INGV (Istituto Nazionale di Geofisica e Vulcanologia) and IGM (Istituto Geografico Militare) carry out measurements (total intensity F, horizontal component H, vertical component Z, declination D and inclination I) over the about 120 repeat stations of the first order magnetic network (Figure 1) The aim of this periodic effort is to replicate magnetic measurements at repeat stations in order to monitor geomagnetic field secular variation and to compute updated coefficients of regional models for representing the main geomagnetic patterns over Italy, at the various epochs. Data of the Italian database wase integrated for the compilation of a sea level shaded relief magnetic anomaly map of total intensity magnetic field for Italy and the surrounding seas, for the geomagnetic epoch 1979.0 [Chiappini et al 2000]. A strong magnetic anomaly circularly shaped that can be seen in the ground level map (panel A), does not show in the aeromagnetic map (panel B)
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