The earthquakes that ripped throughout southern Turkey and northern Syria within the small hours of February sixth have been among the many most devastating of this century. Inside three days of the catastrophe, the reported demise toll surpassed 10,000. This horrifying affect stems largely from shoddy building practices and from the timing of the quake, which occurred whereas folks have been sleeping. However any seismic occasion this highly effective—the largest quakes have been of magnitude 7.8 and seven.5—would inflict grave injury. Worldwide, solely round 15 earthquakes of magnitude seven or better occur annually.
Though Turkey is much from the Pacific “ring of fireplace” that generates a lot of the world’s strongest earthquakes, its neighbourhood is unusually seismically energetic. Quakes are inclined to happen alongside the boundaries between tectonic plates, the segments of Earth’s crust that get moved round by convection currents within the sizzling mantle under. Alongside the fault strains that separate plates, crustal rocks transfer slowly previous one another, usually sticking and jamming. This causes pressure to build up till the fault slips, inflicting an earthquake.
The jap Mediterranean has a very complicated tectonic construction involving a number of “microplates”, together with the Anatolian plate, on which most of Turkey sits. A mere 100m years in the past, this plate comprised a part of the southern shore of a sea known as Tethys, which separated Africa from Eurasia. As this physique of water closed up, leaving the Aral, Black, Caspian and Mediterranean seas as its solely remnants, the Anatolian plate drifted north. It then obtained squeezed between 4 others, together with the Arabian plate to the south-east (which is migrating north) and the Eurasian plate to the north (which is shifting south). Each of those plates are nonetheless pushing into their small Anatolian neighbour right this moment.
Within the wake of a catastrophic earthquake close to Istanbul in 1999, Turkish leaders vowed to enhance seismic preparedness. That tremor originated within the North Anatolian fault, the Anatolian plate’s boundary with the Eurasian plate, which has been the supply of most of Turkey’s giant quakes. In distinction, the East Anatolian fault, the place it rubs up towards the Arabian plate, had not seen a quake of a minimum of magnitude seven since fashionable monitoring methods started within the late nineteenth century.
Many different energetic fault methods, such because the Cascadia subduction zone within the north-western United States and south-western Canada, have gone centuries with out an earthquake. Such relative quiet doesn’t essentially point out low seismic threat. Pressure alongside the East Anatolian fault had been increase 12 months after 12 months, making the fault ripe for a cataclysm. ■
Chart sources: USGS; Christopher Scotese, Paleomap Venture, 2016; “An up to date digital mannequin of plate boundaries”, Peter Hen, 2003; The Economist
