ABSTRACTWe report here the results obtained during a feasibility study that was pursued in order to evaluate the performances of absolute airborne gravimetry. In contrast to relative systems, which use spring‐type gravimeters, each measurement acquired by absolute systems is independent from the others and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and variation of the calibration factor. After a validation of the dynamic performance of the experimental setup in a moving truck, a comparison between the experimental airborne data retrieved over the Swiss Alps and those obtained by ground upward continuation at flight altitude allow us to state that airborne absolute gravimetry is feasible. The first test flight shows a spatial resolution comparable to those obtained by relative airborne gravimetry. For a wavelength on the order of 12 km the absolute value of gravity can be evaluated with an uncertainty of 6.9 mGal.

Terra Nova, 23, 292–299, 2011AbstractThe lithosphere–asthenosphere system of the Italic region in terms of shear‐velocity and density distribution with depth is suitable to investigate the geodynamic context of the region. The velocity structure is obtained through nonlinear inversion of dispersion curves compiled from surface wave tomography on cells 1° × 1° and a smoothing optimization method to choose the representative cellular model, whose layering is used as fixed (a priori) information to obtain a density model by means of linear inversion of gravimetric data. Seismicity and heat flow are used as independent constraints in outlining both the crustal and the seismic lid thickness; the nonlinear moment tensor inversion of recent damaging earthquakes allows some insight in the ongoing kinematic processes. Asymmetry between west‐directed (Apennines) and east‐directed (Alps, Dinarides) subductions is a robust feature of the velocity model, while density model reveals that slabs are not denser than the ambient mantle, thus supplies no evidence for slab pull.

An improved geoid, called ADBVE2006 (Autorita di Bacino di Venezia 2006), has been calculated for the north-east of Italy using new land and marine gravity data together with new high resolution multibeam bathymetric data. A standard processing procedure has been applied to gravity data in order to compute the Free Air and the Bouguer anomalies. The gravity reference datum is IGSN71. The long wave-lenghth part of the gravity field has been modelled by EGM96. The computation has been carried out by the "remove-restore" spectral technique (Stokes' approach) using the software GRAVSOFT. The goal of the calculated model is to improve the geoid estimation in the coastal areas, where the calculated geoids usually suffer from the lack of gravimetric data as well as a good bathymetry.

A shaded relief magnetic anomaly map of total intensity of the Earth's magnetic field for Italy and the surrounding seas has been produced at sea level, for the geomagnetic epoch 1979.0 (see Chiappini et al., 2000). Magnetic observations were made on shore within the framework of Progetto Finalizzato Geodinamica of the Consiglio Nazionale delle Ricerche (PFG-CNR) between 1977 and 1981. The off shore data were taken during the period 1965-1972 by the Osservatorio Geofisico Sperimentale (OGS). This new compilation gives an unprecedented view of the magnetic anomaly field of the whole area at ground level, which contains many imprints of the major tectonic elements of Italy, and portrays their regional characterization. In 2004 Caratori et al. have undertaken a detailed reprocessing of old aeromagnetic data taken by AGIP at the national scale, with the inclusion of new data. For the first time now the ground level map and the aeromagnetic map show the existence of common features that allow comprehensive correct scientific investigations.

An extensive onshore gravity survey, with a nominal density of 1 station/km 2 comprehending 177 stations, has been carried out to improve the existing low- resolution data set in the area surrounding Trieste (Italy). The survey has been processed and the Bouguer anomaly computed over the entire area and then interpreted. The Bouguer anomalies show a negative gravity trend going from south to north probably associated with the regional direction of the main geological structures. According the gravity model computed along six profiles, the regional gravity trend and the minimum negative Bouguer anomaly are related to folding phenomena of the flysch units in the Panzano Gulf and thrusting of limestones over flysch rocks along a fault that outcrops in the "Costa dei Barbari" and runs near the coast southwards. Intraformational deformation cannot be excluded and should be taken into consideration to explain the increase of thickness of flysch northwards.

Releases of endogenous energy, with time variations on the geologic (or eventually even shorter) time scale, are associated with some uplifts of large regional and/or continental space-range, called "superswells". The overlying lithosphere slides down their slopes, over the asthenosphere, over a weak layer "lubricated" by the Joule's heating released by currents leaking off from the geodynamo currents within the Earth's OC. Such kinetic energy is eventually later transformed into friction energy, which supplies geothermal heat flow and/or volcanism. At present, and since a few million years, one such superswell apparently occurs in the Atlantic Ocean, along its MOR, having been responsible for the birth of Iceland. GPS measurements show, essentially "in real time", an approximately eastward sliding of Western Europe, while the sea floor of the Mediterranean is tilted, sloping eastward, as envisaged by the TOPEX POSEIDON measurements of the time variation of sea level. Western Europe collides with Eurasia, causing seismic activity in the Balkan and Italian areas. The phenomenon experiences some irregular temporal trend, and the recorded AE show sporadic occurrences of periods of stress-crises, generally followed by the occurrence, after several months and somewhere within the same area, of some conspicuous earthquake. We discuss a few such examples, which resulted eventually correlated with anomalous behaviour of soil exhalation. Some concrete hints seem to suggest that some anomalous time variations were possible, or maybe even likely, of the geothermal heat flow through such entire area, being the possible prime cause for several apparently anomalous occurrences during the last several years.

Cephallonia Island (Ionian archipelago, west Greece) is located in a tectonically much complex area, prone to conspicuous seismic activity. We report about a multidisciplinary investigation on its geodynamics based on DGPS, DInSAR, DEM, AE, and soil exhalation. A conspicuous earthquake occurred during the measuring period. Such multi-facet approach appears much intriguing, although, upon considering the complexity of the geomorphologic environment, no simple relations ought to be expected. Nevertheless, some interesting features can be envisaged. A wider database, eventually with some better spatial resolution of field records on ground, is likely to permit some deeper insight. Catastrophe prevention requires a realistic observational multidisciplinary approach aimed at monitoring some large number of degrees of freedom, in an attempt at managing particularly complex natural environments.

Acoustic emission is a diagnostic tool of unexpected heuristic potential, although inadequately exploited at present. Its applications deal with the general problem of non-destructive testing of mechanical structures, including a wide span of environmental problems. Some basic methodological items are briefly highlighted. A correct approach in terms of clear concepts is fundamental for an effective and successful application of such a remarkable diagnostic tool.

The science of environment is per se multi- and inter-disciplinary. It is not possible to separate the role of the physical, chemical, biological, and anthropic factors, respectively. Research must therefore rely on suitable natural laboratories, where all different effects can be simultaneously monitored and investigated. Stromboli is a volcanic island slightly North of Sicily, within a tectonic setting characterised by a Benioff zone, curved like a Greek theatre, opened towards the Tyrrhenian Sea, with deep earthquakes. Moreover, it is a unique volcano in the world in that since at least ∼3000 years ago, it has exploded very regularly, about every 15–20 min. Hence, it is possible to monitor statistically phenomena occurring prior, during, and after every explosion. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) has recently established a permanent Laboratory and an extensive interdisciplinary programme is being planned. A few main classes of items are to be considered including: (1) matter exchange (solid, liquid, gas, chemistry); (2) thermal and/or radiative coupling; (3) electromagnetic coupling; (4) deformation; (5) biospheric implications; and (6) anthropic relations since either the times of the Neolithic Revolution. Such an entire multidisciplinary perspective is discussed, being much beyond a mere volcanological concern. We present here the great heuristic potential of such a unique facility, much like a natural laboratory devoted to the investigation of the environment and climate.

In the framework of the European Union SEa Level Fluctuations (SELF) I and the SELF II Projects designed to study sea level variations around the Mediterranean and Black Seas, the Global Positioning System (GPS) technique was adopted to measure the ongoing crustal movements at tide gauge stations. Tide gauges measure sea-level variations with respect to a ground benchmark. In order to determine true sea-level variations of a few millimeters per year, it is necessary to estimate the ground vertical movement to a high degree of accuracy. Countries involved in the projects were Spain, France, Italy, Greece, Bulgaria and Russia. In the period from 1993 to 1998 repeated observations at more than 28 tide gauges and at a number of reference and intermediate stations were conducted. GPS measurements were complemented by Water Vapor Radiometers (WVR) at selected sites. Individual campaigns were evaluated and analyzed and showed height variations in the millimeter–centimeter range. All data were processed following common standards using the Bernese Software in a unified analysis to generate a combined solution. Based on the normal equations of all of the campaigns, a combined solution for the SELF Projects sites was generated. In the analysis of multi-technique anchor sites to the International Terrestrial Reference Frame ITRF97, it is shown that vertical rates of different techniques may be of different sign with respect to each other and also with respect to the ITRF97 combination. Vertical rates are not reliable in general and even the restriction to the use of long the long-time series sites KOSG, ONSA, WTZR, MADR, GRAZ and MATE did not ensure significant and unique vertical rates. Nevertheless, they had to be used for the reference frame definition. The results of repeated gravity observations and the continuous GPS observations at Porto Corsini and Medicina were compared to the epoch-wise GPS campaigns and revealed that the vertical rates are in conformance with each other if taken over the same period in time. The impact of the WVR observations on tide gauge position variation estimation is shown to improve the vertical component in the case of baseline-wise observations with two WVRs by up to 50%. It is shown, that the time span is too short for epoch-type observations to resolve significant height variations. The estimated rates of about 0–20 mm/year are most likely explained by systematic and random errors in the GPS observations. The absolute gravity observations at selected tide gauges are accurate to ±3 μGal and are in general agreement with the zero result from GPS. The main outcome of the SELF campaign observations therefore was the determination of a homogeneous zero-epoch data set and the creation of a database that includes the complete link from the GPS sites to the sea level in the five Mediterranean countries involved.

The fifth in the series of International Comparisons of Absolute Gravimeters (ICAG) was held at the Bureau International des Poids et Measures (BIPM) in November 1997. Fifteen absolute gravimeters participated in the comparison. The mean gravity value obtained at station A (0.9 m) at the BIPM was found to be 980 925 707.8 µGal with a standard uncertainty of 2.8 µGal. This is consistent with the results obtained in previous comparisons at this site. Conclusions based on the analysis of the present results and proposals for future activities are presented.

Magnetic observations made onshore the Italian Peninsula, and across the adjacent seas, have been compiled in a new digital database that provides the first complete regional scale view of the crustal scale magnetic anomalies of the region at sea level. The offshore data were acquired between 1965-1972 by the Osservatorio Geofisico Sperimentale (OGS) while the ground measurements were performed within the framework of the Progetto Finalizzato Geodinamica of the Consiglio Nazionale delle Ricerche (PFG-CNR) between 1977 and 1981. The new shaded relief magnetic anomaly map of total intensity of the Earth's magnetic field for Italy and the surrounding seas has been produced at sea level, for the geomagnetic epoch 1979.0. The most remarkable result of this new map, with respect to the previous compilations and to the aeromagnetic map of Italy, is an unprecedented view of the magnetic signature of the major tectonic elements in their regional setting. There is good correlation between known structural geology and the magnetic anomalies, and now that the longer wavelength signatures have been corrected, deeper interpretations are possible.

We present the results regarding a combined analysis of self-potential and acoustic emission time series, jointly monitored during 1996 by means of a remote station installed north of the town of Potenza, close to an active fault system in a seismic area of Southern Italy. The goal is to verify the existence of correlations between geoelectric and seismoacoustic signals and the local seismicity. Preliminary filtering procedures for the removal of meteoclimatic effects and noise fluctuations of anthropic origin were applied. Then, objective methods were used to discriminate anomalous patterns from background noise in electric and seismoacoustic time series. Finally, a deep analysis of the possible correlations between the self-potential and acoustic emission extreme events and local seismicity has been carried out. The extreme events occurred before the Md = 4.5 earthquake of April 3, 1996 seem to indicate a common physical mechanism likely referable to the dilatancy-diffusion-polarization model.