Thursday, January 14, 2010

Q&A: Haiti Earthquake

By Roger Searle, professor of geophysics, Durham University
Haiti is on a tectonic plate boundary. But we still don't know when earthquakes will strike

The Haiti earthquake was magnitude 7, which releases the energy equivalent to several nuclear bombs. Photograph: Frederic Dupoux/Getty Images

Is it possible to predict earthquakes?

We can predict fairly well where earthquakes may occur. The vast majority occur on or near the boundaries of the tectonic plates that cover the Earth, one of which runs through Haiti. However, most plate boundaries consist of very complex networks of faults, so it is not easy to say which one will move next, although in some instances we can suggest which are more likely to slip. Unfortunately, at present we cannot say just when the next quake will occur.

This earthquake has devastated the poorest houses in the zone, but it has also affected well-designed buildings. How powerful was this earthquake?

The Haiti earthquake was magnitude 7, which releases the energy equivalent of several nuclear bombs. The United States Geological Survey estimates magnitude 7 as equivalent to about half a million tons of high explosive. Each increase of 1 in the magnitude scale is equivalent to 30 times more energy, so this one was only one thousandth of the energy of the magnitude 9.3 earthquake that struck Banda Aceh, in Indonesia, in 2004 and triggered a devastating tsunami.

Is this the biggest earthquake to hit Haiti?

There is a history of earthquakes in Haiti, but the British Geological Survey estimates that the last one of this size was 250 years ago. There are around 50 earthquakes of this size somewhere in the world each year. There were major earthquakes in Haiti in 1860, 1770, 1761, 1751, 1684, 1673 and 1618.

What preparations can be made in areas of risk?

This depends very much on the local authorities, education of the people, and, of course, financial resources. In earthquake zones in highly developed regions such as California and Japan, there are strict building codes to ensure that buildings are, as far as possible, "earthquake resistant". There are also regular drills in schools and elsewhere to teach the safest response during an earthquake: stay indoors until the quake ends; shelter in a doorway or under a table. In areas without building codes, the collapse of homes and offices cause many deaths. Another big problem results from destruction of infrastructure by a quake: roads, communications, water, energy and hospitals are all needed to respond to the emergency. Landslides are common, and can cause significant damage.

Is it possible this area will suffer other earthquakes in the near future?

Smaller aftershocks are occurring now – the USGS measured over 30 up to 14.00 GMT yesterday. I am afraid it is certain that, sooner or later, there will be another big earthquake. It might be soon, or it might not be for hundreds of years.

Additional reporting: Damian Carrington

Source: Guardian.Co.Uk

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