Sargsyan Heghine - Northern Department of the National Survey for Seismic Protection (NDNSSP) of RA, Leningradyan ۵a, Gyumri, ۳۷۷۵۰۰, Republic of Armenia
L. Suvaryan - Gyumri, ۳۷۷۵۰۰, Republic of Armenia

The analysis of strong earthquakes, which occurred after the Spitak destructive earthquake in 1988, shows the connection of seismic effect with the value of the earthquake's energy and its azimuth of spreading. By results of detailed study of damages it is possible to judge about the necessity of the account of such parameters of tremors, as the constitution of frequencies and of its changes during the oscillations, duration of strong oscillations and is probable by the form of oscillations. The listed parameters are confined in time functions (accelerograms), which are the most informative characteristics of the ground's oscillations. The parameters of tremors are depending on parameters of the source of earthquakes - propagation of a rupture and from the properties of the medium, trough that the waves are spreading. We selected the strong earthquakes for study: The Spitak destructive earthquake of 1988 and the all earthquakes, which occurred after the Spitak earthquake, with M і 4.0 in this source zone and the Racha-Djava earthquake on the territory of Georgia which occurred in April 29 of 1991. By the network of equipment SMACH of the ground's strong motions, which were installed during the last period on the territory of Armenia-Georgia, are of registered accelerations of grounds' oscillations. By the records of accelerograms are studied the spectra of oscillations of grounds and are compared with the macroseismic inspections. By the records of accelerograms is proved about the complexity of the source of the Spitak earthquake and about the strong spreading in the northwest direction. The dominant periods of oscillations of earthquakes in the source zone “Spitak-88”.