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The WWSSN long-period body waves of Golbaf and Sirch-Chaharfarsang destructive
earthquakes are analyzed in order to study their source characteristics. Rupture during the Golbaf earthquake initiated in the epicentral area at the northwest part of the activated fault
segment and propagated unilaterally to southeast. The observed complex waveforms of Sirch-Chaharfarsang earthquake are explained in terms of a multiple source consist of at least two
major subevents. Rupture during its source process, initiated near the southeast of its associated surface trace where the first subevent with pure reverse mechanism had occurred and propagated
mainly northwest where the second subevent with a significant lateral component occurred. Regarding the source mechanism of these earthquakes, the shear strain produced by the first
earthquake around the epicentral area of the second earthquake is calculated. Significant accumulation of shear strain preceded the occurrence of the 'second earthquake. This sudden
increase of shear strain, caused by the first earthquake, had an influence on the occurrence of the
second earthquake. Extensive observations might reveal more details about the future activity.