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Last Updated:  Thursday, 6 March, 2003, 11:25 GMT
Clues to future tremors
By Nick Green
BBC Horizon

A new way of forecasting earthquakes has suggested that the Turkish city of Istanbul is likely to be hit by a devastating event in the near future.

Turkey, AP
Thousands were killed in the Izmit quake
The forecast has been made by several teams of scientists who have started investigating a phenomenon called "earthquake storms".

The authorities have been warned and they can carry out preventative measures.

"Buildings can be improved. Construction can be modified. Emergency services can become better organised," said Professor Geoffrey King.

"This will bring the death toll down by 10 times or even a 100 times."

Professor King correctly forecast a huge earthquake that struck the Turkish city of Izmit in 1999.

A year earlier, he had written a paper highlighting the specific earthquake risk to the area. His warnings, though, went unheeded and perhaps 25,000 people were killed.

The work that led to this forecast is featured in the BBC Two science programme Horizon on Thursday.

Shifting stress

One theory suggests earthquakes are random and totally unpredictable.

Ross Stein from the US Geological Survey likens this theory to throwing darts at a board. "One throw doesn't really have very much to say about the next," he said.

But historians studying earthquake history in the Mediterranean started to identify clues that suggested that quakes were not random.

They found that quakes appeared in clusters over a set period of time.

Some scientists have suggested that the end of the Bronze Age could have been triggered by such a cluster. But others believe that a series of quakes rippled across the Mediterranean around AD 365.

It was to describe these incidents that the phrase "earthquake storms" began to emerge.

The problem for science though was finding a mechanism to explain this phenomenon. Then in 1992 an earthquake occurred in the Californian desert at a place called Landers.

Three hours later, another quake struck 40 miles away at the town of Big Bear. Geologist Ross Stein and a team of researchers started investigating if and how these events were linked.

Making a forecast

They produced a map showing that stress had pushed out from Landers and had redistributed around Big Bear. Big Bear was now in an area of heightened stress as a result of Landers.

Geoffrey King, Ross Stein and others started to look at whether the shift of stress could be used to forecast future earthquakes.

Professor King studied 40 earthquakes through Greece and the rest of the Mediterranean and found the majority did appear to have been triggered by shifting stress.

He now believes the faults close to Istanbul are under stress and could be the next to rupture.

Horizon - Earthquake Storms is broadcast on BBC Two in the UK on Thursday at 2100 GMT.




SEE ALSO:
Istanbul quake likely by 2030
27 Apr 00 |  Science/Nature


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