Istanbul that sits on the western end of one of the most energetic fault zones on the planet could be close to the epicentre of the next major quake.

The quake could happen anytime within the next few decades and could be as strong as 7 or more on the scale, according to MIT.

The North Anatolian Fault which has been silent for some time could be preparing for a major quake beneath the Sea of Marmara, a few kilometres west of Istanbul, says a new study.

Tension accumulated in this segment of the fault when released in an earthquake could move the earth by as much as 11 feet within seconds, say the scientists.

It could theoretically also be released in a series of smaller quakes. But going by the history of the fault, a big quake can be expected within the next few decades.

The team from Kandilli Observatory and Earthquake Research Institute in Istanbul and MIT has published their seismic analysis in the journal Geophysical Research Letters.

Scientists began investigating the major fault as it has been silent for some time, indicating that it is either inactive or building up the strain.

Turns out the fault running 745 miles across north Turkey is one whose different segments are undergoing the two different scenarios.

Using GPS data at various locations, the team measured the region's ground movement over the last 20 years. The constant tracking allowed them to see which parts of the crust are moving relative to other parts and to deduce where the strain may lead to a fracture. The movement usually is a harmless sliding, or the slipping in a series of earthquakes.

The Anatolian Fault is moving at about the rate at which a fingernail grows, or about 25 millimetres (one inch) every year. A segment of the fault under the Sea of Marmara, west of Istanbul seems stuck.

The segment which should have slipped about 8 to 11 feet has instead been accumulating strain for the last 250 years. This is the Princes' Island segment which last experienced an earthquake 250 years ago.

The 1999 quake which occurred in the city of Izmit, east of Istanbul lasted less than a minute but killed thousands.