LONDON, March 9 (Reuters) - Scientists have found evidence that an overlooked fault in the eastern Mediterranean is likely to produce an earthquake and tsunami every 800 years as powerful as the one that destroyed Alexandria in AD 365.

Using radiocarbon dating techniques, simulations and computer models, the researchers recreated the ancient disaster in order to identify the responsible fault, they said in a study published in the journal Nature Geoscience on Sunday.

"We are saying there is probably a repeat time of 800 years for this kind of earthquake," said Beth Shaw, a seismologist at the University of Cambridge, who led the study.

Scientists study past earthquakes in order to determine the future likelihood of similar large shocks. Identifying the fault for the AD 365 earthquake and tsunami is important for the tens of millions of people in the region, Shaw said.

The fault close to the southwest coast of Crete last produced a big enough quake to generate a tsunami about 1300, which means the next powerful one could come in the next 100 years, she added in a telephone interview.

Shaw and her colleagues calculate the likely intervals by measuring the motion of either side of the fault to gauge how often such large earthquakes would have to occur to account for that level of motion, she said.

Their computer model suggested an 8 magnitude quake on the fault would produce a tsunami that inundates the coastal regions of Alexandria and North Africa, the southern coast of Greece and Sicily all the way up the Adriatic to Dubrovnik, Shaw said.

This would be similar to the ancient quake in AD 365 that caused widespread destruction in much of Greece and unleashed a tsunami that flooded Alexandria and the Nile Delta, likely killing tens of thousands of people, she said.

"This is consistent with the historical record of the tsunami," she said. (Reporting by Michael Kahn; Editing by Janet Lawrence)

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