The terrestrial crust is a film with the mean thickness of 35 km, and represents the most superficial layer of our planet. The crust is subdivided into continental plates. A great seismic activity has been observed along the lines of the major interactions. Since the last few years the artificial satellites are used to systematically measure the variations of the relative positions of satellite stations placed in tectonically active lines. If one assumes that such relative position variations on the surface are proportional to the elastic deformation degree of the deep rocks, it is theoretically possible to predict when the rocks will reach a compression and tension load beyond which they will disintegrate.
Many earthquakes correspond to the overcoming of the rupture load of the deep rocks.
To date, over 50 orbiting satellites are dedicated to the observation of the Earth. The GPS satellites provide the instant coordinates and the speed of marine, terrestrial and air users. A practical application of great interest of GPS satellites is represented by the possibility to determine in real time the position of lorries and vans for the transport of valuables, in order to know the position of the vehicle in case of theft. Each bus is equipped with a GPS satellite receiver. Many ships, sports craft included, already use the GPS satellites for the navigation.