abstract

A series of shallow earthquakes occurred in northeast Iran starting on November 14, 1979. The sequence includes two destructive earthquakes which occurred on November 14 and 27. In both cases, ground rupture developed along capable faults through the bedrock and Quaternary deposits. The November 14 earthquake was associated with a 20-km N-S trending right-lateral faulting. The November 27 earthquake accompanied a 60-km E-W trending left-lateral fault rupture. Also, during the second earthquake, the northern end of the earlier rupture continued northeastward to align with the eastern end of the second rupture. The result of the fault displacements of both earthquakes is relative subsidence with northeastward/eastward motion of the southwestern block.

The earthquakes are located in the northeast corner of the Lut Block (an eastern fragment of central Iran) and included in the main structural zone of the Central Domain extended from Iran to Central Asia. The recent earthquakes are located in the highly seismic area of northeast Iran where the rate of seismicity has increased markedly in the past decade.

Based on structural considerations of earthquake data, the rupture types their recent migration of locations show that a recent relative eastward motion for east-central Iran blocks resulted from northeast compressional movements and shortening of the Iranian Plateau.

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