Himalaya at risk of major quakes
Saturday 29 December 2012
The Himalayan region of India and Nepal are at a risk of massive earthquakes because of a rupture on the earth surface created by a massive earthquake in 1934. This comes as a surprise because earthquakes in the Himalayan range have not been known to create ruptures on the earth’s surface. But researchers at Nanyang Technical University (NTU) in Singapore, who used radiocarbon dating of riverbed sediments and high-resolution imagery, have found otherwise.
The Indian plate is constantly moving towards the Asian plate creating a major fault called the Main Frontal Thrust (MFT) in Nepal and causing a strain between the plates. Release of this tension resulted in massive, periodic earthquakes in 1897, 1905, 1934 and 1950, with magnitudes between 7.8 and 8.9. The study finds that the split caused by the 1934 quake runs 150 kilometers along the MFT.
“The significance of this finding is that earthquakes of magnitude 8 to 8.5 may return at most twice per millennium on this stretch of the fault, which allows for a better assessment of the risk they pose to the surrounding communities," says Paul Tapponnier, professor at NTU. However, Tapponnier warns that this does not imply that the next earthquake will come after another seven centuries because information on the adjacent segments of the MFT is still elusive. “But it does suggest that areas west or east of the 1934 Nepal ground rupture are now at greater risk of a major earthquake, since there are little or no records of when past earth shattering temblor happened in those two areas,” the professor adds.
The study will be published in the January edition of Nature Geoscience.
With regard to preparedness for earthquake hazards, Thomas Rockwell of the Department of Geological Sciences, San Diego State University, wrote in an accompanying article: “Pinning the details of the rupture down in future work could help develop a more complete view of earthquake hazard in one of the most densely populated seismic zones in the world.”