Follow the latest news on the earthquake in Turkey and Syria
The large earthquake that devastated Turkey and north-western Syria has killed more than 33,000 people, a number likely to rise much further.
Striking before dawn in cold winter conditions with apparently poor building construction and hitting parts of Syria already wrecked by a decade of war, the tremor is among the deadliest quakes of modern times.
The earthquake and its aftershocks are a reminder of the forces that have shaped the wider patterns of human settlement and economy across the Middle East. And they are a warning to be alert to unexpected seismic hazards and properly prepared for infrequent but well-known risks.
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Tectonically, the affected zone is exceptionally complex. It comes at the meeting of the Arabian Plate and the Anatolian Plate, two of the smaller tectonic blocks that comprise the Earth’s rigid outer layer.
The Arabian Plate, originally part of Africa, split off along the lines of the Red Sea and Gulf of Aden to its south-west between 21 and 24 million years ago.
It is bordered on the west by the northern part of the African Plate, the eastern Mediterranean, along the Dead Sea fault. This break runs north to meet the East Anatolian fault. On the north-east, Arabia dives under parts of Turkey and central Iran at the Taurus and Zagros mountains.
The Arabian Plate is bent downwards, where it plunges beneath central Iran and eastern Turkey, while rain and snowmelt on the neighbouring mountains flows into the basin.
This creates the fertile Euphrates-Tigris valley, home of some of the earliest civilisations and the crucial waterway of the Gulf.
It also forms the geological conditions for the generation and accumulation of vast quantities of oil and gas, founding the region’s modern economy and shaping its politics.
The search for hydrocarbons and minerals has enormously advanced geological understanding — including where and why the region’s seismic hazards lie.
Arabia’s boundaries are zones of intense tectonic activity, while there are very few major tremors within the plate’s rigid interior, comprising the GCC countries and most of Yemen, Iraq and Jordan.
Though the UAE is geologically stable, it is not uncommon to feel shaking emanating from Iran, Pakistan and Afghanistan.
Arabia is moving northwards at about 15 millimetres per year. But this minuscule amount is not continuous — it occurs in jerks in different locations.
Field reports from the latest earthquake show roads and railways displaced by about three metres.
The quite small Anatolian Plate is being pressed westwards by this motion, like a watermelon seed squeezed between the fingers.
From the 1930s, there were a series of quakes along the North Anatolian fault, running south of and roughly parallel to the Black Sea coast. These culminated in the 1999 Izmit tremor east of İstanbul, which killed more than 17,000 people.
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South of Istanbul, there is an ominous “earthquake gap”— a segment of the North Anatolian fault that has not moved for 250 years and could be ready for a major shock.
But since 1998, the main activity jumped to the East Anatolian fault with a series of moderate jolts, followed by Monday’s devastating breaks.
Although the epicentre of the first magnitude 7.8 event was near the city of Gaziantep, the break in the fault propagated hundreds of kilometres to the north-east. It occurred at a shallow depth, meaning surface shaking was worse and cut roads, rail, cables and pipelines.
Nine hours later, there was another, even shallower, large quake of 7.5 magnitude on a separate fault to the north, in an area where the Anatolian, Arabian and African plates meet.
This was probably promoted by the transfer of extra stress from the first quake, although the fault must already have been close to rupturing.
Stress is now concentrated at the ends of the broken faults, raising the risk of further quakes. A string of aftershocks, some quite powerful, have brought down already weakened buildings.
The borderlands of the Arabian Plate are no stranger to catastrophic earth movements.
The emperor Trajan narrowly survived a massive earthquake in 115 AD, which destroyed the city of Antioch. The city, one of the Roman world’s greatest, was then heavily struck in 526. Now, as Antakya, it has been ruined yet again.
Iran, a jumble of tectonic blocks squashed between the Arabia, Eurasia and Indian plates, is no stranger to tremors.
Its deadliest of modern days killed 50,000 in northern Iran in 1990, and 26,271 died in the ancient city of Bam in 2003.
The megacity of Tehran, built on the soft sediments washed down from the Alborz Mountains, faces a terrifying seismic risk which has led to periodic talk of moving the capital to the safer location of Isfahan.
Egypt generally seems tectonically quiescent.
But an unsuspected fault running from the Gulf of Suez rift zone, a branch of the Red Sea, lies buried under Nile sediments.
In October 1992, it ruptured near Cairo, in a moderately sized earthquake that was deadly and damaging because of the shaking of mostly older buildings on soft ground.
Another potentially dangerous fault, unknown until recently, underlies Beirut, possibly responsible for a major tremor of 551.
The Dead Sea fault, where it runs through Galilee and the Bekaa Valley, caused damaging shocks in 1202, 1759, 1837 and, well-remembered, 1956.
Crete, where the Mediterranean crust subducts under the island, was the source of huge tsunamis in 365 and 1303, smashing the Egyptian and Levantine coasts and dislodging the Great Pyramid’s white casing stone.
Another underappreciated risk is of a tsunami in the Gulf of Oman, triggered where the Indian Ocean Plate descends under the Makran coast of Iran and Pakistan.
Such an event struck about 1,000 years ago, with boulders of 100 tonnes deposited on the Omani coast by waves up to 50 metres high.
The testaments of past and present catastrophes illustrate the dangers, some well-known, others obscure.
The geological foundations that have built this region are more fragile than they might appear.
To limit the terrible human toll, Arabia’s borderlands need to set proper building standards, enforce them, warn rapidly of shocks and tsunamis, and be prepared to respond to emergencies.
Robin M. Mills is chief executive of Qamar Energy, and author of The Myth of the Oil Crisis