Published on December 30th, 2012 | by Joshua S Hill1
Himalayas Should Prepare For Mammoth Earthquakes
Such a finding is of critical importance to the region, a region which has a similar population density to that of New York City but with far fewer governmental resources.
“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,” said Professor Paul Tapponnier of the Nanyang Technological University in Singapore.
The study, published in the journal Nature Geosciences, showed that two specific quakes – one in 1255 and another in 1934 – were in fact ground-breaking quakes, rather than ‘blind quakes’, earthquakes that did not rupture the surface.
The region is not hidden from earthquakes, having suffered quakes of magnitude 7.8 and higher in 1897, 1905, 1934 and 1950. However these quakes were all thought t be blind quakes.
Prof Tapponnier, however, combined new high resolution imagery and ‘state of the art dating techniques’ to determine that the 1934 earthquake did in fact rupture the surface, breaking the ground over a length of more than 150 kilometres.
This surface rupture formed along the main fault in Nepal that is the current boundary between the Indian and Asian tectonic plates, known as the Main Frontal Thrust (MFT) fault.
Despite the massive gaps between the two quakes Prof Tapponnier and his team found, the professor warns that there is no need to become lax thinking that the next earthquake is not for many years to come.
“This does not imply that the next mega-earthquake in the Himalayas will occur many centuries from now because we still do not know enough about adjacent segments of the MFT Mega-thrust,” Prof Tapponier explains. “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 last earth shattering temblor happened in those two areas.”
Prof Tapponnier will now attempt to determine the full extent of the fault ruptures in an effort to build a more comprehensive model of earthquake hazards along the Himalayan front.