Enormous earthquakes ‘are missing’ from records

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.

Scientists are scanning historical documents for the lost tremors.

The findings are presented at the American Geophysical Union Fall meeting in San Francisco.

Dr Susan Hough from the US Geological Survey said: “If you try to make a statistical case there are too few earthquakes in the 19th Century.”

Earthquakes measuring more than M8.5 cause immense devastation.

Recent examples include the 2004 quake in the Indian Ocean that unleashed a deadly tsunami, Chile’s massive 2010 earthquake, and the 2011 event in Japan.

But records before the 20th Century are strangely devoid of natural disasters on this scale.

‘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Researchers use historical documents to track down seismic events that occurred before this and assess their magnitude.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.  TRUNews