The study of historical earthquakes not only allows the collection of their characteristics in appropriate catalogues but also the identification of the areas at risk. A map of maximum intensity associated with large earthquakes of the past supplies a first approximation of the main trends of regional seismicity during historical times, while in principle the investigation of active faults allows the region's seismogenic potential to be assessed directly and independently of the presence of people and civilizations. The study of seismic waves propagation, generated by earthquakes and recorded by seismograms, gives 3D images of the earth inner structure.
Seismic tomography is a method for delineating the seismic wave- velocity within the earth.
Recent geophysical studies allowed us to recognize the evolution of the Italian peninsula within the Mediterranean area and the relative movements of the Euro-Asiatic and African plates. The monitoring of the upper atmosphere has important applications in radio-communications and in environmental problems.