A 'mega earthquake' is likely to strike the Himalayas this century, causing catastrophic landslides and floods and killing more than 40,000 people, Indian and US geologists have warned.
Scientists from the National Geophysical Research Institute of India and Stanford University, United States, analysed the fault that separates the Asian and Indian continental plates.
Images of the Main Himalayan Thrust (MHT) fault showed that a segment of it dips downwards by 15 degrees, and is steeper and further north than suggested by previous observations. This dip could rupture and cause an earthquake of magnitude 8 or more, often referred to as a mega earthquake.
- Researchers analysing the Himalayan fault in more detail than ever before have predicted a 'mega quake' is likely
- Such a quake in the Kathmandu area would kill tens of thousands of people
- Deaths could be avoided by building earthquake-resistant buildings, and developing and enforcing building codes
The researchers predict that the segment will break over a larger area of the fault and create a larger magnitude earthquake than previously thought.
"The larger the area of the fault that breaks, the more energy is released, and the larger the magnitude of the earthquake," says Simon Klemperer, professor of geophysics at Stanford University and co-author of the work.
"It will happen — the question is when. I would be very surprised if we didn't have a magnitude 8 earthquake somewhere along the Himalayan Front this century."
The study, presented at the American Geophysical Union Fall Meeting in San Francisco earlier this month (7 December), measured ground movements. By placing seismometers closer together in one area, the researchers have been able to produce a more detailed image of the MHT.
Klemperer says a big earthquake would start at the top of the sloping segment. "This is in central Nepal — where Kathmandu is — but such a big earthquake would devastate a much larger area."
"This would cause huge landslides, some of which would dam rivers, and produce large lakes. There would be catastrophic floods," he says.
Brian Tucker, president of GeoHazards International, an organisation that works to improve the seismic safety of Bhutan, northern India, Nepal and Pakistan, agrees that a large earthquake would occur.
"We estimated about 40,000 people would die in Kathmandu Valley alone if such a large earthquake struck Nepal 15 years ago when the population of the Kathmandu Valley was about 1.5 million. Since then the population has multiplied many fold and the quality of construction has in general worsened," he tells SciDev.Net.
Tucker said that to prevent large-scale damage, new hospitals and schools should be designed and built to be resistant to earthquakes, and existing buildings should be strengthened, as well as "developing and enforcing appropriate land use plans and modern building codes".