garv

 

Gravity

All methodological aspects of 3D modelling and inversion of gravity data and development of new software. Different approaches are used, which include spectral methods, upward-downward continuation methods, iterative methods, direct modeling by simple geometric objects or polyhedral objects, topographic reduction. 3D modeling with the aid of GIS functions and 3D visualisation, in the frame of the IGMAS software. Another topic of interest is retrieval of depth of the sources. Range of applications: from small superficial anomalies of prospecting and environmental interest to deep, extensive regional masses. Both terrestrial, ship borne and satellite derived gravity measurements are used.

 

Crustal structure

The crustal structure of different areas are studied, ranging from Tibet plateau, Himalaya, Karakorum, Alps, Brasil. We apply gravity inversion combined with results from active or passive seismological investigations. In particular the undulations of the Moho or other strong density discontinuities are retrieved, as e.g. the Model of Moho undulations in Tibet, obtained in the frame of Italian-Chinese cooperation. A further topic is the study of isostatic conditions, applying the lithospheric flexure models.


Crustal movements

The earth is in continuous movement, on time scales of some fraction of second, to almost static movements. These movements give way to a deformation of the crust that can be observed with very sensitive instruments, as the ones of the Grotta Gigante and of the Friuli strain-tilt network. Measurements made underground, record weak signals that cannot be detected otherwise. Some examples are the earth tides due to moon-solar gravitational forces, the deformation due to the weight of the oceans or the atmospheric pressure column, the deformations due to surface or subsurface water movements, the eigen-vibrations of the earth, the deformations that accompany the build-up of an earthquake, and in general all deformations related to tectonic plates movements. We are interested in all topics related to the observation, modeling and interpretation of these signals.


Seismic precursors

A great challenge in Geophysics is to be able to give some prediction regarding the realization of a seismic event. The problem is approached by direct instrumental monitoring of endangered areas and by statistical evaluation of the seismicity in time and space. The observation of deformation by geodetic instrumentation (tilt and strain meters, GPS) is one experimental method, and a great problem is to determine very carefully what the effects are that disturb the observations, as is the atmospheric pressure, the water table variations, the temperature, and the rainfall. The great pendulums gave interesting signals in the three years preceding the 1976 disastrous Friuli earthquake: starting with 1973 a disturbing signal appeared on both the NS and EW pendulums, that intensified the amplitude and duration until 1976, when it stopped suddenly with event. In the months later the signals appered again, but gradually expired, and have not been observed since.

 

Deformation anisotropies

The welth of deformational data collected by the Friuli strain-tilt network instruments in the last 25 years, since the most recent Friuli destructive earthquake, provide an excellent opportunity to construct an anisotropic model of the uppermost Earth's crust in the area to describe its seasonal behavioural peculiarities.

 

Lithospheric flexure

The lithospheric flexure model is based on the deformation of a thin elastic plate by loading on the top, bottom or within the plate. The deformation of the plate depends on the flexural parameters which can be determined by analyzing the crustal loads and the crustal deflection. The flexural parameters vary spatially and have characteristic values in different parts of the earth. Over sea areas the flexural rigidity depends on the age of the ocean plate at the time of loading. Combined with the gravity inversion the flexure analysis becomes a powerful system to study the earth structure. Flexure studies require application of 2D spectral analysis and 2D filtering methodologies.


Informazioni aggiornate al: 18.12.2007 alle ore 09:11