M 7.1 - 27 km NNE of Van, Turkey

Tectonic Summary

Turkey is a tectonically active country that experiences frequent destructive earthquakes. On a broad scale, the seismotectonics of the region near the October 23, 2011, earthquake are controlled by the collision of the Arabia plate and Eurasia plates; at the location of this event, the Arabia plate converges with Eurasia in a northerly direction at a rate of approximately 24 mm/yr. West of the October 23, 2011, earthquake, tectonics are dominated by strike-slip faulting on the East (in southern Turkey) and North (in northern Turkey) Anatolian fault zones. These large, translational fault systems extend across much of central and western Turkey and accommodate the western motion of the Anatolian block as it is being squeezed by the converging Arabia and Eurasia plates. In the area of Lake Van and farther east, tectonics are dominated by the Bitlis suture zone (in eastern Turkey) and Zagros fold and thrust belt (towards Iran). The October 23, 2011, earthquake occurred in a broad region of convergence beyond the eastern extent of Anatolian strike-slip tectonics. The focal mechanism solution of this earthquake is consistent with oblique-reverse faulting similar to mapped faults in the region. Of the two possible fault orientations of the focal mechanism solution, finite-fault modeling of globally recorded seismic data is more consistent with slip on the west-striking (north-dipping) reverse fault.

This earthquake is a reminder of the many deadly seismic events that Turkey has suffered in the recent past. The devastating Izmit earthquake of 1999 (M 7.6) ruptured a section of the North Anatolian fault 1,000 km to the west of the October 23rd event and caused 17,000 fatalities and 50,000 injuries, and left 500,000 people homeless. Approximately 70 km from this earthquake, a M 7.3 earthquake occurred in November 1976 destroying several villages near the Turkey and Iran border and resulted in several thousand fatalities. A M 7.8 earthquake struck Erzincan in 1939, with an estimated 33,000 fatalities.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)