SOURCE ANALYSIS OF THE ۱۹۷۹ GHAENAT, NORTH-EAST IRAN, EARTHQUAKES

The WWSSN long period body waves of the two destructive earthquakes of Ghaenat were inverted to their sources to study the complexity of their source mechanisms. The results of analysis suggest that the first earthquake is a single event while the second einhquake is a multiple shock which consists of two major subevents. Mechanismis of the subcvents are consistent with the observed fault movements and aftershock activities. Taking into account the source mechanişm of these earhquakes, the shear stain produced by the first earthquake in the focal region of the second earthquake is calculated. Significar of shear suain preceded the occurrence of second earthquake. It is suggested that the increase of shear strain caused by the first earthquake has possibly an effect on the occurrence of the second earthquake. This effect of stain accumulation might be related to the beginning of the precursory process. Hence, the accumulation of seismic shear strain is an important factor in the occurrence of these intra-plate earthquakes and it could be one of the criteria for prcdic. von of these earthquakes. According to this study if the general trend of earthquakegenerating stress system is known, the area where shear strain may have been accumulated for a certain period, by preceding earthquakes, can be found. Temporal observations in these areas might reveal the possibilities of occurrences of forthcoming earthquakes.