The results of spectral analysis of maximum entropy method from spatialtemporal variations of the gravity field and the relationship between them and earthquakes

The issue of space migration of time variations of the gravity field of non-tidal type arose in<br>connection with reports on observations of space migrations of fronts of deformational stresses within the<br>Earth’s crust. For example, when studying the materials of the China strong earthquake in ref. (Sholz,<br>1977), the space migration velocity was estimated of the front of deformational stresses of rock within the<br>Earth’s crust for a ten-year period. According to these estimations, the front of deformational stresses<br>extended over the territory of China from the west toward the east with a velocity of 110 km/year. Similar<br>estimations for the velocity of natural displacement of the zones of deformational stresses (10–100<br>km/year) have been observed in Turkey (Mogi, 1968), Japan, USA (Kasahara, 1979). The question arises<br>of whether or not migration of the time variations of the gravity field is one of the manifestations of the<br>migration of the front of deformational stresses registered by other geophysical methods. To answer this<br>question, we consider the papers of other authors. In the context of a search for earthquake precursors, a<br>number of authors (Sadovsky et al., 1972; Talwani, 1979; Sherburne, 1979) have performed an<br>investigation of variations of different geophysical parameters in time, of migration of these parameters in<br>space, and of the relationship between them and elastic stresses occurring during earthquakes. Therefore,<br>on the basis of elasticity theory it may be deduced that the search for methods of earthquake prediction<br>should be reduced to the search for the ways of revealing and extracting elastic stresses and processes<br>related to them. Therefore, in order to increase the reliability of earthquake prediction, the results of<br>repeated yearly measurements of the gravity field over a network of sites of seismically dangerous thickly<br>populated regions are suggested to be used as complementary to the magnetic method. Repeated<br>gravimetric measurements over the set of points offer the advantage that they permit embracing most of<br>a seismically active region and in such a manner conducting measurements close to the future earthquake<br>epicenter, where the non-tidal variations of the gravity field can have the maximum values in contrast<br>with deformographs, which are, as a rule, located at a considerable distance from the future earthquake<br>epicenter and, thus, exhibit weakly manifested seismic effects that do not permit predicting earthquakes<br>reliably.