What caused Monday's major earthquake in Turkey? Here's what we know

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STEVE INSKEEP, HOST:

The earthquake that struck Turkey this week did not surprise many seismologists who study the region and its fault lines. So why was the region not better prepared? NPR's Geoff Brumfiel has more.

GEOFF BRUMFIEL, BYLINE: To understand what just happened, here's the big picture. The Arabian Peninsula is making its way north into the Eurasian Plate, and the entire nation of Turkey is getting squeezed aside. Michael Steckler is at the Lamont-Doherty Earth Observatory at Columbia University.

MICHAEL STECKLER: Arabia is slowly moving north and has been colliding with Turkey. And Turkey is moving out of the way to the west.

BRUMFIEL: This earthquake occurred at the junction of several faults involved with that tectonic push.

STECKLER: It's a pretty busy and complicated area.

BRUMFIEL: But Turkish seismologists had suspected that at some point, there was going to be a big quake in this region.

FATIH BULUT: This is not surprise for us.

BRUMFIEL: Fatih Bulut is a seismologist at Bogazici University in Istanbul. Bulut says stress has been building up in this part of Turkey for hundreds of years. His team and others have been predicting an earthquake about this size, though they couldn't say exactly when it would happen. The quake was the kind that occurs when two parts of the earth slide past each other. As a result, the damage has spread along the fault line.

BULUT: It is quite large. know. Like, 10 cities are affected, structurally affected, in Turkey.

BRUMFIEL: Turkey and Syria have been at the epicenter of earthquakes for a millennia, including a quake that flattened the Syrian city of Aleppo in 1138. Turkey now has seismic codes to try and keep buildings standing. But Bulut says because this area hadn't been hit hard for centuries, it's quite possible that some of the buildings predate the codes.

BULUT: Sometimes there are very old things built before these rules exist.

BRUMFIEL: Steckler adds that he believes some construction in Turkey circumvents the rules.

STECKLER: I know, certainly in Istanbul, there's a lot of illegal construction that goes on that - and people not following the building codes.

BRUMFIEL: Strong aftershocks are continuing to rock the region. Steckler says he expects they may go on for a while.

STECKLER: That whole area - all the pieces of the earth will slowly adjust and break and rupture and come to a new equilibrium.

BRUMFIEL: While the people above struggle to come to grips with the devastating aftermath of this powerful quake.

Geoff Brumfiel, NPR News.

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