Earthquake to Fill in Istanbul's 'Seismic Gap?'

When a segment of a major fault line goes quiet, it could possibly be the calm before the storm. Researchers worry that Istanbul's "seismic gap" is a warning that a major earthquake may soon occur off the country's coast, according to a new study.

A seismic gap could possibly be inactive - the result of two tectonic plates placidly gliding past each other - or it could be the source of a potential earthquake.

To determine if Istanbul will be the next target of a major earthquake, researchers from the Massachusetts Institute of Technology (MIT) and Turkey used GPS data to measure the region's ground movement over the last 20 years. The North Anatolian Fault - one of the most energetic earthquake zones in the world - stretches for about 745 miles across northern Turkey and into the Aegean Sea.

Although it's impossible to pinpoint when an earthquake will ensue, researcher Michael Floyd believes this next one - likely to occur along a seismic gap beneath the Sea of Marmara, five miles west of Istanbul - could be a magnitude 7.0 or stronger.

"Istanbul is a large city, and many of the buildings are very old and not built to the highest modern standards compared to, say, southern California," Floyd, from MIT's Department of Earth, Atmospheric and Planetary Sciences, said in a press release. "From an earthquake scientist's perspective, this is a hotspot for potential seismic hazards."

Based on collected data, Floyd and his colleagues found a segment of the fault under the Sea of Marmara that has been moving at a rate of 10 to 15 millimeters per year. This "missing" slip, called the Princes' Island segment, hasn't experienced an earthquake for 250 years. At first glance it may not seem like a threat, however researchers indicate that the segment should have slipped about 8 to 11 feet, but hasn't. If this building tension were to break, it could result in a cataclysmic earthquake that shakes Istanbul, causing the Earth to shift by as much as 11 feet within seconds.

Although it's possible this strain could be released in a series of smaller, less devastating quakes, based on the region's history, that's not likely. The researchers expect a large earthquake off the coast of Istanbul within the next few decades.