Understanding 7.2 Van earthquake

Understanding 7.2 Van earthquake

Night is falling and it makes difficulties to all that was hit by 7.2 Van earthquake.  Death toll is expected to rise because there is lots of people trappen in collapsed buildings and the cold makes harder to survivers.

EMSC registered 7.3 magnitude at depth of 15km, USGS registered 7.2 magnitude at depth of  GFZ Postdam registered 7.1 magnitude at depth of 15km, Iran Seismological Center registered 7.1 at depth of 18km, AFAD DEPREM registered 6.7 magnitude at depth of 19.2 km, Kandilli Observatory registered 6.6 magnitude at depth of 5km .

There have been 104 aftershocks over M2.7 so far. 22 aftershocks over M4. 5 aftershocks over M5 with latest M6.



USGS PAGER issued RED ALERTfor shaking-related fatalities and economic losses. High casualties and extensive damage are probable and the disaster is likely widespread. Past red alerts have required a national or international response. Estimated economic losses are 0-4% GDP of Turkey. Estimated modified Mercalli intensity is Degree IX. It indicates that masonry structures and poorly constructed buildings suffer serious damage or collapse, frame structures, if not bolted, shift off foundations, serious damage to reservoirs, underground pipes broken, conspicuous cracks in the ground, in alluvial areas, sand and mud ejected and sand craters are formed.

Overall, the population in this region resides in structures that are a mix of vulnerable and earthquake resistant construction. The predominant vulnerable building types are unreinforced brick masonry and nonductile reinforced concrete frame construction. The power has not been restored so far.



Kandilli Observatory ELER says taking into account the number of buildings that become uninhabitable = 3200-3400, severely damaged buildings = 600 and completely collapsed buildings =  50; 500-700 deaths is the approximate estimate. News from rural locations has not been collected but damage is estimated at around 60-70 percent. The governor the Van province has setup a ‘coordination center’ in Ercis to cope with this crisis. Civil Defense and Red Crescent teams from the region have reached the area.

The death toll is unchanged since many hours at 85 but will certainly increase within the next 4 to 24 hours. A lot of people are still buried under the debris of the collapsed houses. A lot of people are leaving the cities and are heading for family in the rural areas. They fear the narrow streets with medium rise apartment buildings. (EarthquakeReport)




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. (USGS)


Strike-slip faults




The fault surface is usually near vertical and the footwall moves either left or right or laterally with very little vertical motion. Strike-slip faults with left-lateral motion are also known as sinistral faults. Those with right-lateral motion are also known as dextral faults.




A special class of strike-slip faults is the transform fault, where such faults form a plate boundary. These are found related to offsets in spreading centers, such as mid-ocean ridges, and less commonly within continental lithosphere, such as the Alpine Fault, New Zealand. Transform faults are also referred to as conservative plate boundaries, as lithosphere is neither created nor destroyed.



Earthquakes in Turkey

Present-day earthquakes range from barely perceptible tremors to major movements measuring five or higher on the open-ended Richter scale. Turkey's most severe earthquake in the twentieth century occurred in Erzincan on the night of 1939-12-27; it devastated most of the city and caused an estimated 33,000 deaths.  The earthquake of seven violent shocks, the biggest one measuring 8.2 on the Richter scale, was the most powerful one to strike Turkey in recent history.

Earthquakes of moderate intensity often continue with sporadic aftershocks over periods of several days or even weeks. The most earthquake-prone part of Turkey is an arc-shaped region stretching from the general vicinity of Kocaeli to the area north of Lake Van on the border with Armenia and Georgia.

List of earthquakes in Turkey






Lake Van

The lake's outlet was blocked at some time during the Pleistocene, when lava flows from Nemrut volcano blocked westward outflow towards the Muş Plain. Mt. Nemrut is the most southern and youngest of the chain of volcanoes in eastern Anatolia. It is a stratovolcano, and began erupting during the fourth geological era and continued to be active until 1597 A.D. As a result of the volcanic eruptions of Mt. Nemrut, the single Van — Mus river basin was divided into two separate basins. The eruption of Nemrut volcano also led the formation of Lake Van, the largest lake in Turkey. Now dormant, Nemrut Dağı is close to the western shore of the lake, and another dormant stratovolcano, Süphan Dağı dominates the northern side of the lake and it is the second highest volcano in Turkey, after the mount Ararat.

The water level of the lake has often altered dramatically: near Tatvan, a raised beach high above the present level of the lake as well as recently drowned trees. Investigation by Degens and others in the early 1980s determined that the highest lake levels (72 metres (236 ft) above the current height) had been during the last ice age, about 18,000 years ago. About 9,500 years ago there was a dramatic drop to more than 300 metres (980 ft) below the present level. This was followed by an equally dramatic rise around 6,500 years ago.



Similar but smaller fluctuations have been seen recently. The level of the lake rose by at least three metres during the 1990s, drowning much agricultural land, and (after a brief period of stability and then retreat) seems to be rising again. The level rose about two meters in the ten years immediately prior to 2004.

As a deep lake with no outlet, Lake Van has accumulated great amounts of sediment washed in from surrounding plains and valleys, and occasionally deposited as ash from eruptions of nearby volcanoes. This layer of sediment is estimated to be up to 400 metres (1,300 ft) thick in places, and has attracted climatologists and vulcanologists interested in drilling cores to examine the layered sediments.

Geology of Turkey

Turkey's varied landscapes are the product of complex earth movements that have shaped Anatolia over thousands of years and still manifest themselves in fairly frequent earthquakes and occasional volcanic eruptions. Except for a relatively small portion of its territory along the Syrian border that is a continuation of the Arabian Platform, Turkey geologically is part of the great Alpine belt that extends from the Atlantic Ocean to the Himalaya Mountains. This belt was formed during the Tertiary Period (about 65 million to 1.6 million B.C.), as the Arabian, African, and Indian continental plates began to collide with the Eurasian plate, and the sedimentary layers laid down by the prehistoric Tethyan Sea buckled, folded, and contorted. The intensive folding and uplifting of this mountain belt was accompanied by strong volcanic activity and intrusions of igneous rock material, followed by extensive faulting during the Quaternary Period, which began about 1.6. million B.C. This folding and faulting process is still at work, as the Turkish and Aegean plates, moving south and southwest, respectively, continue to collide. As a result, Turkey is one of the world's more active earthquake and volcano regions.



Earthquakes range from barely perceptible tremors to major movements measuring five or higher on the open-ended Richter scale. Earthquakes measuring more than six can cause massive damage to buildings and, especially if they occur on winter nights, numerous deaths and injuries. Turkey's most severe earthquake in the twentieth century occurred in Erzincan on the night of December 28-29, 1939. Earthquakes of moderate intensity often continue with sporadic aftershocks over periods of several days or even weeks. The most earthquake-prone part of Turkey is an arc-shaped region stretching from the general vicinity of Kocaeli to the area north of Lake Van on the border with Armenia and Georgia.



Turkey's terrain is structurally complex. A central massif composed of uplifted blocks and downfolded troughs, covered by recent deposits and giving the appearance of a plateau with rough terrain, is wedged between two folded mountain ranges that converge in the east. True lowland is confined to the Ergene Plain in Thrace, extending along rivers that discharge into the Aegean Sea or the Sea of Marmara, and to a few narrow coastal strips along the Black Sea and Mediterranean Sea coasts. Nearly 85 percent of the land is at an elevation of at least 450 meters; the median altitude of the country is 1,128 meters. In Asiatic Turkey, flat or gently sloping land is rare and largely confined to the deltas of the Kizilirmak River, the coastal plains of Antalya and Adana, and the valley floors of the Gediz River and the Büyükmenderes River, and some interior high plains in Anatolia, mainly around Tuz Gölü (Salt Lake) and Konya Ovasi (Konya Basin). Moderately sloping terrain is limited almost entirely outside Thrace to the hills of the Arabian Platform along the border with Syria.

More than 80 percent of the land surface is rough, broken, and mountainous, and therefore is of limited agricultural value. The terrain's ruggedness is accentuated in the eastern part of the country, where the two mountain ranges converge into a lofty region with a median elevation of more than 1,500 meters, which reaches its highest point along the borders with Armenia, Azerbaijan, and Iran. Turkey's highest peak, Mount Ararat (Agri Dagi)--about 5,166 meters high--is situated near the point where the boundaries of the four countries meet. (CountryStudies)



Plate tectonics

Except for a relatively small portion of its territory along the Syrian border that is a continuation of the Arabian Plate, Turkey geologically is part of the great Alpine belt that extends from the Atlantic Ocean to the Himalaya Mountains. This belt was formed during the Tertiary Period (about 65 million to 1.6 million B.C.), as the Arabian, African, and Indian continental plates began to collide with the Eurasian Plate. This process is still at work today as the African Plate converges with the Eurasian Plate and the Anatolian Plate escapes towards the west and southwest along strike-slip faults. These are the North Anatolian Fault Zone, which forms the present day plate boundary of Eurasia near the Black Sea coast and, the East Anatolian Fault Zone, which forms part of the boundary of the North Arabian Plate in the southeast. As a result of this plate tectonics configuration, Turkey is one of the world's more active earthquake and volcano regions. (Wikipedia)

Comments

MARIO 8 years ago

One of the big EQ of the year, that it seems the Arabian is interaction with the eurasian plate on the top. Some scientists say that the reason is the african acting in the south west of the arabian and indian, what produce EQ in the Himalayas and Turkey, moving the Indian continent to the north and Anatolia to the west. May be.....Anyway we have to sorry the deaths and the destruction, always in poor countries and people.

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