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.


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