ИСТИНА

Numerous works are devoted to the problem of the relationship between earthquake magnitude and the spatial characteristics of the source. The empirical relationships between source parameters and magnitude make it possible to theoretically understand how those or other model representations of processes in the earthquake source correspond to reality. This paper presents the results of analysis of the spatial distribution of repeated shocks. Data from the world earthquake catalog of USGS/NEIC from 1973 to 2014 were used. Short time intervals, no more than 10 hours after the main shock, and distances from the epicenter of the main shock, no more than 5°, were considered. The dependence of the number of repeated shocks on the distance from the epicenter was studied. Two properties of the spatial distribution of repeated shocks have been identified. The first property is that the curve describing spatial distribution has its maximum at a certain distance (approximately from 10 to 120 km) from the epicenter of the main shock. The logarithm of this distance is directly proportional to the magnitude of the main shock. The second property is that the position of the maximum does not depend on time, i.e., it is a stable spatial characteristic of the earthquake source. Based on these properties, a new way to determine the size of the rupture zone was proposed. We received the regression relation between characteristic size of focal zone and the main shock magnitude lgLkm=0.43M-1.27. It corresponds well with the analogous relation of Yu. Riznichenko (1976) lgLkm=0.44M-1.29 but considerably differs from the relation lgLkm=0.67M-2.9 offered by D. Wells and K. Coppersmith (1994). This work was supported by RFBR project No. 18-05-00096 and by the State Assignment Programs of the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences.