Abstract

Focal mechanism solutions are determined for 23 earthquakes that occurred from 1965 to 1970 in Persia, Turkey, Pakistan, and Afghanistan. These mechanisms were obtained from the long-period first-motion P waves recorded by the World-Wide Standardized Seismograph Network stations. Mechanism solutions for the earthquakes in the folded foothills of the Zagros are predominantly thrust faulting, but depending on the assumed crustal velocity, many have strike-slip components. Cross sections of the seismic zone of the folded foothills of the Zagros show that the earthquakes are confined to a possible lithospheric slab nearly 60 km thick dipping 10° to 20° toward the north. For the earthquakes with focal depth of about 200 km, in the Hindu Kush in Afghanistan, mechanism solutions are characterized by a nearly horizontal compressional axis and a steeper extensional axis. The seismic zone appears as a contorted slab-like structure 20 to 30 km in width. This lithospheric slab may be a remnant of the Tethys Sea floor. Consistent right-lateral strike-slip mechanism solutions are found for earthquakes on the Anatolian fault in Turkey. For earthquakes on the Ferdows fault in eastern Persia, mechanism solutions vary from pure left-lateral strike-slip faulting to pure thrust faulting. Mechanism solutions for earthquakes on the Kirthar-Sulaiman shear zone in West Pakistan show consistent left-lateral strike-slip motion on a fault plane that strikes north-south. This is in agreement with the northward movement of India with respect to Afghanistan. On the basis of seismic and geological evidence, the entire Middle East is divided into eight plates which are moving northward, at different rates, with respect to Eurasia. The differential motion between various plates can explain the sense of offset and other geological features.

You do not currently have access to this article.