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2011.10.23 - M7.2 Eastern Turkey

At least 534 people killed, 2,300 injured and 14,618 buildings and homes destroyed or damaged in the Ercis-Tabanli-Van area. Telecommunications, electricity and water services disrupted. Felt throughout eastern Turkey, Armenia, Georgia, Azerbaijan and northwestern Iran and parts of Iraq, Syria, Lebanon, Jordan and Israel.NEIC Event Executive Summary

Mw 7.2   Eastern Turkey
October 23, 2011 10:41:21
Version 2

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 are controlled by the collision of the Arabian Plate and Eurasian plates; at the latitude of this event, the Arabian 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 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 (toward 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 similar to 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 this earthquake a M7.3 earthquake occurred on November 11, 1976 destroying several villages near the Turkey and Iran border and killing several thousand people. A M7.8 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 M7.3 earthquake near the Turkey-Iran border that killed between 3,000-5,000 people

Historical Seismicity
M7.6 August 17, 1999 Izmit, Turkey Earthquake
Location: 40.7N 30.0E
This earthquake, which killed 17,000 people and injured more than 50,000, struck western Turkey on August 17, 1999 (also known as the Kocaeli, Turkey, earthquake) and occurred on one of the world's longest and best studied strike-slip (horizontal motion) faults: the east-west trending North Anatolian fault. Maps of Turkey and California show how that the North Anatolian and San Andreas faults are very similar. This fault is very similar to the San Andreas fault in California. This similarity has lead to active scientific collaborations between scientists in Turkey and the US aimed at understanding the hazards we both face. A comprehensive U.S.G.S. report about this earthquake, its effects, and its implications for future hazard in both Turkey and the United States is available on line (pdf format, 6MB).

M7.3 November 23, 1976 Turkey-Iran border region
Location: 39.1N 44.0E
The earthquake was located along the Turkish-Iranian border
region. It is estimated that between 3,000-5,000 people were killed
and many injured. Caldira, Muradiye, and surrounding villages
near the Iranian border were completely destroyed. Snow and
bitter cold weather hampered the rescue teams from reaching many
of the mountainous villages. Some casualties and damage were
reported in northwestern Iran. The shock was also reported felt
in the area of Yerevan, Armenia.

M7.8 December 26, 1939 Erzincan, Turkey
Location: 39.8W 39.4W
This earthquake killed 32,700 people and did extreme damage in the Erzincan Plain and the Kelkit River Valley. Damage (VII) occurred from near Turcan, where a strong earthquake (possibly a fore- shock) had occurred on Nov 21, west to Amasya and from Sivas north to the Black Sea coast. The quake was felt strongly at Larnaca, Cyprus. Over 300 km (190 mi) of surface faulting was observed in the North Anatolian Fault Zone between Erzincan and Niksar, with as much as 3.7 m (2.5 ft) of horizontal displacement and 2.0 m (1.2 ft) of vertical offset. A small tsunami was observed at Fatsa on the Black Sea coast of Turkey. It was recorded by tide stations from Tuapse, Russia to Sevastopol, Ukraine. 

Style of Faulting: Thrust

Centroid Moment Tensor
11/10/23 10:41:21.73

Epicenter:  38.710   43.446
MW 7.3

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

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 IX  377K
MMI X   29K

Reported Damage
Turkish authorities are reporting more than 40 collapsed structures in the region. Hardest hit was the town of Ercis, Turkey near the Iranian border.

Links to News Articles

USGS Event Link

Prompt Assessment of Earthquakes for Response

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