Nearly 20 earthquakes of magnitude greater than 7 have struck Turkey in the past century. The most recent one, which struck southern Turkey on Monday, is the most powerful to hit the country since 1939, when a 7.8-magnitude earthquake devastated the northeast. It also is the deadliest in more than 80 years.
As of Friday morning, the confirmed death toll had surpassed 22,000 in Turkey and Syria, and it is expected to rise as rescue teams continue digging through crumbled buildings. In 1999, a 7.4-magnitude tremor in Kocaeli province, 60 miles outside Istanbul, killed more than 17,000.
Worldwide, the quake is among the 20 deadliest over the past century and the worst since 2010, when a 7.0-magnitude earthquake in Haiti killed more than 300,000 people.
The high death toll in Syria and Turkey results from a combination of factors: the power and size of the earthquake, its proximity to densely populated areas, and it shallow point of origin below the surface of the Earth. Monday’s earthquake originated only 11 miles deep, which means that seismic waves took a short time to reach the surface. Earthquakes that occur deeper in the earth are less destructive because they lose some strength by the time their energy reaches the surface.
Turkey has a long history of destructive tremors. The country sits at the intersection of three major tectonic plates — the Arabian, Anatolian and African. As the plates move and squeeze against each other, they put pressure on their fault zones, which are cracks in the earth’s crust. This movement builds stress that is released suddenly from time to time, resulting in earthquakes.
Historically, much of Turkey’s seismic activity happens in the north, a region that’s closely watched because of its proximity to Istanbul, which has a population of 15 million. Since 1900, dozens of quakes have originated along the northern fault, many of them over magnitude 7.
Earthquakes along the East Anatolian Fault are less common. Monday’s quake was one of about a dozen to occur there in the past hundred years, none greater than magnitude 7. Seismological experts told The Washington Post that the lack of recent earthquakes along that fault and the northward movement of the Arabian plate led to pent-up strain in the region, which caused a vertical fracture in the Earth’s crust.
Number of casualties as of 12 p.m. Eastern, Feb. 10.
Sources: Global Significant Earthquake Database from NOAA’s National Centers for Environmental Information, United States Geological Survey (USGS).
Editing by Samuel Granados and Reem Akkad.