USGS NEIC Event Executive Summary

Mw 7.2   Eastern Turkey

October 23, 2011 10:41:21


Version 1



38.63N 43.49E Depth 20km


Location Last Updated at 10/23/2011 07:09:33  (Mountain Time)

Event Coordinator: Benz, Harley M.(benz@usgs.gov)

Nearest Cities


19 km (12 miles) NE (43°) from Van, Turkey 
116 km (72 miles) N (351°) from Hakkari, Turkey 
130 km (81 miles) SSE (161°) from Karakose (Agri), Turkey 
192 km (119 miles) SSW (206°) from YEREVAN, Armenia

Tectonic Summary


Turkey is a tectonically active country that experiences frequent destructive earthquakes. On a broad scale, the seismtectonics of the region near the October 23, 2011 earthquake is controlled by the collision of the Arabian Plate and the Eurasian Plate with northerly convergence of the Arabian plate at a rate of approximately 24 mm/y. West of the October 23, 2011 earthquake the tectonics is dominated by strike-slip faulting on the East and North Anatolian fault zones. These large fault systems extend across much of central and western Turkey accommodating the western motion of the Anatolian block as it is being squeezed by the converging Arabian and Eurasian Plates. In the area of Lake Van and further east, tectonics are dominated by the Bitlis Suture Zone in eastern Turkey and Zagros fold and thrust belt of 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 of today’s earthquake is consistent with oblique-thrust faulting on a south-southwest trending fault, similar to the trend of mapped faults in the region. 

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) broke a section of the North Anatolian Fault 1000 km to the west of the October 23 event and killed 17,000 people, injured 50,000, and left 500,000 homeless. Approximately 70 km from the October 23, 2011 earthquake a M7 earthquake occurred on November 11, 1976 destroying several villages near the Turkey and Iran border and killing several thousand people. A M8.0 earthquake struck Erzincan in 1939, killing an estimated 33,000 people.

Talking Points

•  Complex region of faulting dominated by compressional tectonics associated with the Bitlis Suture Zone and Zagros Fold and Thrust belt

•  Generally east-west trending thrust fault with waveform controlled depth of 20 km

•  Within about 70 km of the November 11, 1976 M7 earthquake that killed 3,900 people

Historical Seismicity


Within approximately 400 km of the epicenter there have been 3 destructive earthquakes since the mid-1970s. These were 

1975/09/08 M6.7 MMI(max)VIII Deaths: 2,370 Dist from epi: 241 km 
1976/11/24 M7.0 MMI(max)IX Deaths: 3,900 Dist from epi: 66 km 
1992/03/13 M6.6 MMI(max)IX Deaths: 498 Dist from epi: 358 km

Style of Faulting: Thrust

Centroid Moment Tensor


11/10/23 10:41:21.73 

Epicenter:  38.710   43.446 
MW 7.3 

USGS CENTROID MOMENT TENSOR 
11/10/23 10:41:44.50 
Centroid:  39.451   43.354 
Depth  16         No. of sta: 159 
Moment Tensor;   Scale 10**19 Nm 
  Mrr= 5.89       Mtt=-6.13 
  Mpp= 0.24       Mrt= 7.73 
  Mrp= 1.60       Mtp=-0.51 
 Principal axes: 
  T  Val=  9.83  Plg=63  Azm=344 
  N        0.22       4       81 
  P       -10.05      26      173 

Best Double Couple:Mo=9.9*10**19 
 NP1:Strike= 80 Dip=71 Slip=  86 
 NP2:       272     19       101

W Phase Moment tensor
11/10/23 10:41:21 

Epicenter:  38.627   43.534 
MW 7.2 

USGS/WPHASE CENTROID MOMENT TENSOR 
11/10/23 10:41:21.00 
Centroid:   38.527   43.790 
Depth  11         No. of sta: 89 
Moment Tensor;   Scale 10**19 Nm 
  Mrr= 5.09       Mtt=-5.75 
  Mpp= 0.66       Mrt=-4.00 
  Mrp=-3.80       Mtp=-0.45 
 Principal axes: 
  T  Val=  8.07  Plg=60  Azm=118 
  N     = -0.65      19      248 
  P     = -7.43      20      346 

Best Double Couple:Mo=7.8*10**19 
 NP1:Strike=108 Dip=30 Slip= 133 
 NP2:       240     69        68

PAGER Population Exposure
MMI VI  482K 
MMI VII 265K 
MMI VIII 67K 
MMI IX  377K 
MMI X   29K

Reported Damage
Preliminary reports of collapsed structures in Van, Turkey and widespread outage of power and communication

Links to News Articles
http://www.msnbc.msn.com/id/45005013/ns/world_news-europe/ 
http://www.bbc.co.uk/news/world-europe-15421633 
http://www.hurriyetdailynews.com/n.php?n=quake-hits-se-turkey-2011-10-23

USGS Event Link
     http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usb0006bqc/

Prompt Assessment of Earthquakes for Response
      http://earthquake.usgs.gov/earthquakes/pager/events/us/b0006bqc/index.html

If there are any changes, suggestions, questions, or comments about this particular email, please contact benz@usgs.gov