A research team led by Nanyang Technological University (NTU) has discovered that powerful earthquakes measuring 8 to 8.5 on the Richter scale have left clear scars in the central Himalayas. This discovery has huge implications for the area along the front of the Himalayas, given that the region has a population density similar to that of New York City, researchers said in a statement.
Paul Tapponnier, a leading neotectonics scientist, said that signs of earthquakes in the past means that tremblors of the same magnitude can occur again in the region, especially in areas which have yet to have their surface broken.
The study showed that in 1255 and 1934, two great earthquakes ruptured the ground surface in the Himalayas. This runs contrary to what scientists previously thought.
Tapponnier said that by combining new high resolution imagery and state-of-the-art dating techniques, they could show that the 1934 earthquake did indeed rupture the surface, breaking the ground over a length of more than 150 km, essentially to the south of that part of the range that comprises Mount Everest.
This break formed along the main fault in Nepal that currently marks the boundary between the Indian and Asian tectonic plates — also known as the Main Frontal Thrust fault.
Using radiocarbon dating of offset river sediments and collapsed hill-slope deposits, the researchers managed to separate several episodes of tectonic movement on this major fault and pin the dates of the two quakes.
Tapponnier warns that the long interval between the two recently discovered earthquake ruptures does not mean people can be complacent.
Massive earthquakes are not unknown in the Himalayas, as quakes in 1897, 1905, 1934 and 1950 all had magnitudes between 7.8 and 8.9, each causing tremendous damage. But they were previously thought not to have broken the earth’s surface — classified as blind quakes — which are much more difficult to track.
The study by Tapponnier and his team along with scientists in Nepal and France was published recently in Nature Geosciences.