Time to shift view of seismic risk - experts

May 22, 2011
Knowledge of seismic risk is badly skewed in favour of earthquakes that occur on plate boundaries, such as the March 11 temblor that hit northeast Japan, rather than those that strike deep inland, a pair of scientists said. Philip England of Oxford University and James Jackson of Cambridge University say that in seismic terms, the 9.0-magnitude Sendai quake was "a remarkable story of resilience."

Knowledge of seismic risk is badly skewed in favour of earthquakes that occur on plate boundaries, such as the March 11 temblor that hit northeast Japan, rather than those that strike deep inland, a pair of scientists said on Sunday.

In commentary appearing in the journal Nature Geoscience, Philip England of Oxford University and James Jackson of Cambridge University say that in seismic terms, the 9.0-magnitude Sendai quake was "a remarkable story of ."

Good civic training and building construction meant that the death rate was "impressively low," they said. Around 25,000 people died, or 0.4 percent of those exposed to the event, and most of these died from the tsunami that followed.

The March 11 event occurred on a , where the jigsaw of plates that float on Earth's crust jostle and grind and slide under each other.

England and Jackson say plate boundaries are relatively well-studied, but a far greater threat lurks in continental inland areas.

" in earthquakes within continental interiors have often exceeded five percent and can be as high as 30 percent," they warn.

According to their count, over the past 120 years, there have been around 130 quakes around the world where a thousand people or more have died.

Of these, about 100 have occurred in continental interiors, causing 1.4 million deaths, whereas earthquakes at plate boundaries have inflicted 800,000 deaths, roughly half of them by tsunamis.

Among the inland killers were those in Bam, Iran, which cost 30,000 lives in 2003; in Muzzafarabad, Pakistan, which led to 75,000 deaths in 2005; and the 2008 Wenchuan quake in China in 2008 in which 70,000 died.

An aerial picture shows a view of the tsunami-devastated the town of Ishinomaki, Miyagi prefecture in April 2011. Good civic training and building construction meant that the Japanese earthquake's death rate was "impressively low," scientists said. Around 25,000 people died, or 0.4 percent of those exposed to the event, and most of these died from the tsunami that followed.

The main reason for these high tolls is because inland zones are poorly mapped, the commentary says.

Their faults are often very complex and slow-moving, sometimes taking hundreds or even thousands of years to build up tension to the point where they rupture.

Jackson and England call for the study of inland faults to be given the same priority as boundary faults, starting with the 10 million square kilometres (3.86 million sq. miles) of the Alpine-Himalayan belt, which stretches from Italy, Greece and Turkey, across the Middle East, Iran and central Asia, to China.

"The severity of this threat is increasing rapidly as millions of people every year migrate into mega-cities in vulnerable locations, many of which were devastated by earthquakes in the past, when their populations were much smaller."

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Sue_Ann_Bowling
5 / 5 (1) May 22, 2011
I think whoever rewrote this for PhysOrg is a little confused as to the difference between intraplate (e.g, New Madrid) and intracontinental (Himalayan-Alpine zone) earthquakes. The Himalayan-Alpine zone is a result of plate collisions of the continent-to continent type (Indian, Arabian and African plates against the Eurasian plate) which are admittedly not as well understood as collisions of the oceanic-continental type (Japan, W South America, S Alaska) or the transform type (California.) But these are not intraplate earthquakes.
rwinners
not rated yet May 23, 2011
Emphasis is placed upon plate boundary quakes because that is where most quakes occur. If another "new Madrid" quake occurs, then emphasis will be place upon rebuilding to new codes in the effected areas, based upon the seismic information from that quake. But, not before. We humans simply do not place that much importance on preventing 'any' loss of life. There are too many examples to name.