This week’s deadly earthquake was the latest in a string of major temblors that have struck northern Turkey progressively from east to west over the past 60 years.

Scientists had long considered Izmit, where the Tuesday’s quake was centered, to be a danger zone. “There is no question in the community that this was an area of stress buildup,” says Nafi Toksoz, a geophysicist at Massachusetts Institute of Technology.

Earthquake Chain
In 1939, a magnitude-8.0 earthquake struck near the eastern city of Erzincan, rupturing 225 miles of the North Anatolian fault that cuts across northern Turkey. Then, from 1942 to 1967, five more major quakes struck, each rupturing a part of the fault to the west of the previous quake. There have also been a couple of earthquakes to the east of the 1939 quake.  “It follows up the trend of the other earthquakes,” Toksoz says of the latest earthquake. The fault rupture starts right where the 1967 rupture ended, he says.  “It’s a pattern that has long been recognized,” says Jim Dieterich, a senior scientist at the U.S. Geological Survey in Menlo Park, Calif. “There’s a progression of earthquakes that have now marched across much of northern Turkey.”

Dieterich was one of the authors of an August 1997 article in Geophysical Journal International that looked at whether one earthquake helped set off subsequent ones, and which areas might be susceptible to future earthquakes.