French-Turkish researchers detect early quake signals

Mar 23, 2011 by Michel Sailhan

Franco-Turkish researchers have found that a deadly 1999 earthquake in Turkey was preceded by seismic signals, raising hopes of a predictive system for future tremors as Japan reels from its disaster.

Studying copious data from the period just before the hit Turkey's northwestern Kocaeli province on August 17, 1999, the discovered what they dubbed a "preparatory phase" lasting 44 minutes.

"This is a very special seismic signal, corresponding to a deep and slow sliding of the fault, a vibration that goes on for 44 minutes," said team member Michel Bouchon, research director at the National Centre for Scientific Research, France (CNRS).

"This trend continued until the , increasing its intensity," he told AFP.

The earthquake, which measured 7.6 on the Richter scale, devastated Turkey's most industrialised region, including some suburbs of Istanbul, and killed some 20,000 people.

The voluminous data on the quake had previously prevented the discovery of the seismic signals of the preparatory phase, Bouchon said.

"One can say that abnormal activities precede nearly half of major earthquakes, suggesting the presence of a preparatory phase," he said.

In the 9.0 magnitude tremor that hit Japan earlier this month, "abnormal was detected in the two days preceding the quake," Bouchon noted.

"But it was 100 kilometres (60 miles) offshore," which made it difficult to detect the warning signals, he said.

Istanbul's 13 million inhabitants live in constant fear of a major earthquake, which experts say will hit Turkey's largest metropolis in the near future with a magnitude of up to 7.2.

An alert 44 minutes prior to a major tremor would be critical to saving lives as it would allow people "to gather in open spaces such as parks or squares in a city like Istanbul," which is poorly prepared for seismic risks, Bouchon said.

"With the means we have today, it is difficult to identify these preparatory stages. It might be possible in the future," he said, however.

A preface to the research team's study published last month in the US magazine Science warned: "Scientists are eager to find clues that may tell them when large earthquakes are imminent, but whether these particular findings apply to other earthquakes remains an open question."

Hayrullah Karabulut, a team member from Istanbul's Bogazici University, was equally cautious over any imminent prospect of an early warning system.

"We need to check with other examples, other earthquakes before drawing any conclusions," Karabulut said.

Even if the researchers conclude that their findings could apply generally to other earthquakes, that would not be sufficient to set up an alarm system for Istanbul, according to Karabulut.

"The problem would still be to install high-quality seismographs deep in the Marmara Sea (an inland sea connecting the Black Sea to the Aegean Sea) for the future Istanbul quake, which would be extremely difficult," he said.

Explore further: Researchers construct a model of impact for El Nino / La Nina events

add to favorites email to friend print save as pdf

Related Stories

Underwater gas may hold clues on Turkey quake risk

Dec 15, 2009

Natural gas that lies under Turkey's Marmara Sea close to Istanbul could provide advance warning of an earthquake experts believe will hit the country's largest city, scientists said on Tuesday.

New study sheds light on quake peril for Istanbul

Jan 18, 2010

An investigation into a perilous fault that runs south of Istanbul suggests it could unleash two or three big quakes in a series rather than an extremely large one-off event, as some studies have feared.

Istanbul warned of potential earthquake

Jan 05, 2006

Researchers say a major earthquake is likely to strike Istanbul over the next 30 years, and are recommending immediate action to protect the city.

Ill. earthquake a wake-up call

Apr 20, 2008

A U.S. seismologist said the earthquake that jolted the Midwest Friday is a reminder of the risks seismic events pose outside familiar quake areas.

Recommended for you

The ocean's living carbon pumps

9 hours ago

When we talk about global carbon fixation – "pumping" carbon out of the atmosphere and fixing it into organic molecules by photosynthesis – proper measurement is key to understanding this process. By ...

User comments : 0