The main objective of the present study is to evaluate seismic attenuation relationships for the Campanian area (southern Italy) using the felt intensity report data obtained from comprehensive historical databases (DOM 4.1). We focused our attention on the Campania region because it is characterized by a high seismic hazard and risk, particularly in the Naples area and its suburbs. In order to derive an attenuation relationship for the area, we fitted the observed data by using several functions. We found that a linear plus logarithmic model gives the best fits for the data in the Campanian region. Most of the attenuation relationships proposed up to now for the Italian Peninsula have an isotropic behavior and do not always properly describe the macroseismic attenuation. Therefore, in order to check the possible dependence of the attenuation on the azimuth of the seismic rays, we divided our data set in octants and performed for each of them the same analysis we carried out for the whole data set. The obtained results differ from octant to octant and the differences, besides being associated with the source effects, could be interpreted as probably due to the existence of lateral variations in the lithological and physical features of the crust at different depths, which could affect the patterns of attenuation.

In this paper we present an approach for evaluating landslide susceptibility in seismic areas. It is known that earthquake-induced landslide susceptibility is related to several, often interplaying, factors. Nevertheless, an effective grade-2 zonation should be characterized by a good balance between simplicity, quickness and reliability. The GIS-based procedure we present employs only three factors that we believe are the most significant in this susceptibility assessment: the type of outcropping rocks/soils, the slope angle and the MCS intensity. The local annual precipitation, certainly an essential factor, is considered here as a parameter whose seasonal pattern is constant in time and space. Each of the three parameters is expressed as a Significance percentage and the resulting Seismic Landslide Susceptibility level of an area is given by the average of the significances of the first two factors multiplied by the significance of the third factor. The procedure was set and tested on the volcanic island of Ischia (southern Italy), which was affected by several historical earthquake-induced landslides. The results of this susceptibility zonation test at Ischia show a very good match between the distribution of the sources of historical landslides and the areas we identified as the most susceptible ones.

In this paper we present a study of the structural setting of the volcanic island of Ischia by the analysis and interpretation of high-resolution aeromagnetic and self-potential data recently acquired over the island. The magnetic data allowed us to locate the main anomaly sources and lineaments of the island and its offshore surroundings, while the self-potential (SP) data provided information on both the structural pattern of the resurgent caldera and the high-temperature fluid circulation. An inversion of the acquired magnetic and SP data, and a joint modelling of the magnetic data and of a previous gravity data set along a SW-NE profile allowed us to build a model of the island. The model is characterized by the presence of an igneous-very likely trachytic-structure, whose top is located at 1200-1750 m b.s.l. Such a body, possibly formed by several neighbouring intrusions, has a density contrast with the pyroclastic cover of about 0.4 gr/cm(3) and its central-western part, below Mt. Epomeo, seems to be demagnetized. The demagnetization should be connected to the high geothermal gradient measured in this portion of the island and may be due to hydro-chemical alteration processes and/or to the possible presence of partially melted spots within the intrusion. Our outcome is consistent with the results of previous geophysical, geo-volcanological and geothermal studies. (c) 2008 Elsevier B.V. All rights reserved.

This paper presents a study of the Phlegrean Fields-Ischia submarine ridge by the analysis and interpretation of high-resolution aeromagnetic data recently acquired in the Western Procida offshore. The investigated area is located along the ridge connecting Ischia to the Phlegrean Fields and is characterized by the existence of several monogenetic volcanoes aligned on a NE-SW system of faults. The high-resolution magnetic data yielded new information on the area, highlighting particularly the signature of a volcanic body located between Pt. Serra and the Ruommoli shoal. This structure has not been clearly described before and we named it as the Pt. Serra submarine volcano. The computation of the analytic signal and horizontal gradient of the data distinctly located this structure and definined the position of its rims. A 2D modeling and 3D inversion of data provided information on the volcano’s thickness, width and magnetization, disclosing a meaningful igneous body extending down to several hundred meters b.s.l.

An application of magnetic survey to the submerged Roman ruins of the Bay of Baia, volcanic area of the Phlegrean Fields, Naples (southern Italy) is presented and discussed. The site of Baiae, one of the most extensive submerged archaeological sites known in Italy, is characterized by urban sites with residential houses, thermal baths, fisheries and harbour buildings. The survey was aimed to establish the typical magnetic signatures of building structures submerged in a volcanic marine environment. The comparison of both the maps of the magnetic anomaly field and of the computed analytic signal with the known submerged archaeological structures of the area gave some interesting insights into the lithological characteristics of the archaeological structures of the Baiae site and showed the effectiveness of the magnetic method for mapping remnants of building structures beneath the sea bed. Copyright © 2005 John Wiley & Sons, Ltd.

In this paper we present an example of the integration of airborne and marine magnetic data sets measured in the Neapolitan area, southern Italy. The integration involved detailed data measured recently in the Phlegrean Fields, in the Somma-Vesuvis area and in the Bay of Naples, that produced a high-resolution magnetic map of the whole active volcanic district. The data sets partially overlapped and characterized varying flight height and line spacing. Integration was therefore performed through several procedures including continuation between general surfaces. The integration produced a new, detailed, draped magnetic data set of the Neapolitan region characterized by a terrain clearance of 200 m, giving a meaningful overall view of the volcanic area. The study of the main magnetic features of the area was carried out by computing the horizontal gradient of the pole-reduced draped data. The analysis of the obtained map showed the presence of lineaments of preferential magma upwelling and buried volcanic structures and allowed the delineation of a geovolcanological and structural framework of the whole Neapolitan volcanic district.

We here present and discuss the results of the analysis and qualitative interpretation of two magnetic surveys performed in the Bay of Naples in 1998 and 2000. A map of the Bay of Naples based on the data acquired during these surveys has already been published by the Italian CNR-IAMC Research Institute. We re-processed the same data to produce maps of the pole reduced, analytic signal and horizontal derivative data and correlated them with the bathymetry and the gravimetric data of the area. The analysis shows strong anomalies in the NW and NE volcanic areas of the Bay of Naples, while the central area seems magnetically quiet. In the Phlegrean area the maps clearly show the southern rim of the Phlegrean caldera and demonstrate that while the Magnaghi Canyon is correlated to gravimetric highs and magnetic structures, and can therefore be interpreted as an active lineament, most of Dohrn Canyon is not characterized by volcanic activity and does not correlate to any gravimetric or magnetic structures. An important round-shaped magnetic anomaly is for the first time identified in the central slope of the gulf between the two canyons, probably correlated to a large buried volcanic edifice. In the Vesuvian area some intense circular anomalies, aligned in the NNW–SSE direction, are localized in the Torre del Greco and Torre Annunziata offshore, related to the submerged part of Vesuvius and possibly connected to buried vents.