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Enormous earthquakes ‘are missing’ from records
By Rebecca Morelle
Science reporter, BBC World Service
The Earth could have been struck by many more huge earthquakes in its recent history than was previously thought, scientists say. Research suggests that half of all quakes measuring more than 8.5 in magnitude that hit in the 19th Century are missing from records...
'Warnings from history'
"Seismometers were developed around 1900. As soon as we had them, earthquakes started to look bigger," explained Dr Hough.
Researchers use historical documents to track down seismic events that occurred before this and assess their magnitude.
Dr Hough believes that many large earthquakes in the 18th and 19th Century have been missed.
The earthquake in Haiti in 2010 killed more than 100,000 people One reason for this is because there is a general assumption that earthquakes measuring M8.5 and above generate significant tsunamis.
"But this isn't always the case, and the magnitudes for some of these earthquakes has been underestimated," said Dr Hough.
A candidate is a quake that hit Kamchatka in Russia in 1841. Its magnitude had been thought to be 8.3, but now Dr Hough believes it should be upgraded to M9.2.
Another is a quake that struck in the Lesser Antilles in 1843.
Dr Hough said: "This was catalogued at a low magnitude 8. It turns out it was felt by a quarter of the globe."
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