Researchers pointed out the possibility of a future earthquake on the North Anatolian Fault, which stretches for 745 miles across northern Turkey and into the Aegean Sea.
When a segment of a fault line goes quiet it can either mean the "seismic gap" is inactive or it is the source of a potential earthquake and is building tension, Massachusetts Institute of Technology (MIT) reported. Researchers found both types of behavior on different segments of the North Anatolian Fault, which is similar in scale to California's San Andreas Fault.
To make their findings the researchers looked at 20 years of GPS data along the fault and determined the next earthquake will most likely occur about five miles west of Istanbul.
"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," said Michael Floyd, a research scientist in MIT's Department of Earth, Atmospheric and Planetary Sciences. "From an earthquake scientist's perspective, this is a hotspot for potential seismic hazards."
It's impossible to predict exactly where an earthquake will occur or how strong it will be, but the researchers said the future Istanbul earthquake could have a magnitude of 7 temblor or higher.
"When people talk about when the next quake will be, what they're really asking is, 'When will it be, to within a few hours, so that I can evacuate?' But earthquakes can't be predicted that way," Floyd said. "Ultimately, for people's safety, we encourage them to be prepared. To be prepared, they need to know what to prepare for - that's where our work can contribute."
Over the past few decades earthquakes have occurred on the North Anatolian Fault in a "domino-like" fashion, moving from the east to the west. The most recent occurred in 1999 just east of Istanbul; the initial shock killed thousands of people.
In order to predict where the next fracture may occur the researchers used GPS of ground movement over the past 20 years.
"By continuously tracking, we can tell which parts of the Earth's crust are moving relative to other parts, and we can see that this fault has relative motion across it at about the rate at which your fingernail grows," Floyd said.
The team estimated the North Anatolian Fault moves at about one inch per year. Fault models pinpointed a segment under the Sea of Marmara that is slipping by only about 15 millimeters per year. This section, dubbed the "Prince's Island segment" should have slipped by between eight and 11 feet by now, but has failed to do so. If the tension were to break in an earthquake the land could slip by as much as 11 feet in only a matter of seconds.
"The nucleation point is pretty close to the city center, which makes early warning time pretty short - between two to six seconds," said Marco Bohnhoff, a professor at the German Research Center for Geosciences in Potsdam, Germany. "Since the international airport is located in an area where ground motion would be high, it would be difficult to get in emergency troops, and unfortunately 90 percent of buildings in Istanbul do not fulfill building codes, and might not resist the expected earthquake."
The findings were published in a recent edition of Geophysical Research Letters.
