Abstract
In this paper we present and analyze the new detailed aeromagnetic data set resulting from a recent survey car- ried out in the Phlegrean Fields volcanic area. The survey was aimed at gaining new insight into the vol- canological characteristics of the region north of Phlegrean Fields (Parete-Villa Literno area) where remarkable thickness of volcanic/sub-volcanic rocks were found in wells. Measurement of total magnetic field was per- formed on two different flight levels, 70 m and 400 m above the ground surface, along flight lines spaced 400 m apart. Both aeromagnetic maps show the noisy effect of linear anomalies evidently due to the presence of rail- way lines. To filter out these local anomalies a method based on discrete wavelet transform was used, allowing an accurate local filtering and leaving the rest of the field practically unchanged. The filtered data set was inte- grated with the existing Agip aeromagnetic map of the Phlegrean Fields, leading to a new aeromagnetic map of the whole Phlegrean volcanic area. The compilation of the pole reduced map and of the maps of the Analytic Signal and of the Horizontal Derivative of the integrated data set represents a first step for the interpretation of the maps in terms of geological structures of the whole Phlegrean volcanic district.
Highlights
The areas of Parete and Villa Literno, located north of the Phlegrean Fields (Naples, Italy) are characterized by the presence of intense magnetic anomalies with wavelength of tens of km and by a remarkable thickness of volcanic rocks, as observed in geothermal well data
The structural pattern of the Phlegrean Fields results from the superimposition of two caldera collapses related to the Campanian Ignimbrite (CI) (36000 years old) and the Neapolitan Yellow Tuff (NYT) (12000 years old) eruptions (Orsi et al, 1996)
The flight section contained: i) a cesium magnetometer having a precision of 0.01 nT, which was contained in a «bird» flown 30 m below the helicopter; ii) a GPS sensor for the horizontal positioning of the helicopter, having a precision of ±1 m after the differential correction; iii) a laser-altimeter for the vertical positioning of the helicopter, and iv) a computer for data acquisition
Summary
The areas of Parete and Villa Literno, located north of the Phlegrean Fields (Naples, Italy) are characterized by the presence of intense magnetic anomalies with wavelength of tens of km (fig. 1) and by a remarkable thickness of volcanic rocks (about 1.5 km of basaltic and andesitic lavas were found in the Parete 2 Well), as observed in geothermal well data In the last 5000 years the major tectonic event was a localized uplift inside the caldera, in the area of the town of Pozzuoli (e.g., Orsi et al, 1996) The expression of this uplift is the 3 km long marine terrace of La Starza, a fossil marine cliff running parallel to the coastline. The subsidence was interrupted only by some uplift phases, like the one before the Monte Nuovo eruption and the bradyseismic crises of 1969-1972 and of 19821984, which caused a total maximum uplift of about 3.3 m in the central area of the Phlegrean Caldera (Civetta, 1996) These uplifts have been accompanied by intense seismic activity with epicenters localized in the city and bay of Pozzuoli and by persistent fumarolic activity. Composite data sets allow a more complete view of patterns and trends that individual data sets may not provide
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