14 March 2011

Japan earthquake and large deviations

The New York Times has an interesting article today about how Japan and North America came closer together after the devastating earthquake last week.

A very important area of study in modeling is that of large deviations theory. When we collect data in order to model something-- in order to predict earthquakes, for example-- we may not get very many data points for rare events, if any at all. Researchers in this area work on theory that allows for principled extrapolation to model and predict rare events.

From the article:

"What is perhaps most surprising about the Japan earthquake is how misleading history can be. In the past 300 years, no earthquake nearly that large — nothing larger than magnitude-eight — had struck in the Japan subduction zone. That, in turn, led to assumptions about how large a tsunami might strike the coast.

“It did them a giant disservice,” said Dr. Stein of the geological survey. That is not the first time that the earthquake potential of a fault has been underestimated. Most geophysicists did not think the Sumatra fault could generate a magnitude-9.1 earthquake, and a magnitude-7.3 earthquake in Landers, Calif., in 1992 also caught earthquake experts by surprise.

“Perhaps the message is we should re-evaluate the occurrence of superlarge earthquakes on any fault,” Dr. Stein said."