A research team led by
scientists from Nanyang Technological University (NTU) has discovered that
massive earthquakes in the range of 8 to 8.5 magnitudes on the Richter scale
have left clear ground scars in the central Himalayas.
This ground-breaking discovery has huge implications for the area along the
front of the Himalayan Mountains, given that the region has a population density
similar to that of New York City. NTU Professor Paul Tapponnier, who is
recognised as a leading scientist in the field of neotectonics, said that the
existence of such devastating quakes in the past means that quakes of the same
magnitude could happen again in the region in future, especially in areas which
have yet to have their surface broken by a temblor.
Published recently in Nature Geosciences, the study by NTU's Earth Observatory
of Singapore (EOS) in Singapore and colleagues in Nepal and France, showed that
in 1255 and 1934, two great earthquakes ruptured the surface of the earth in the
Himalayas. This runs contrary to what scientists have previously thought.
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.
However, Prof 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
kilometres, essentially south of the part of the range that harbours Mt 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 (MFT) fault.
Using radiocarbon dating of offset river sediments and collapsed hill-slope
deposits, the research team managed to separate several episodes of tectonic
movement on this major fault and pin the dates of the two quakes, about 7
centuries apart. "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 Prof Tapponnier.
Prof Tapponnier warns that the long interval between the two recently discovered
earthquake ruptures does not mean people should be complacent, thinking that
there is still time before the next major earthquake happens in the region.
"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." The
next step for Prof Tapponnier and his EOS scientists is to uncover the full
extent of such fault ruptures, which will then allow them to build a more
comprehensive model of earthquake hazard along the Himalayan front.
About the NTU's Earth Observatory of Singapore (EOS)
EOS is a premier research institute at NTU, Singapore, which conducts
fundamental research on earthquakes, volcanic eruptions, tsunami and climate
change in and around Southeast Asia, towards safer and more sustainable
societies. Funded by the National Research Foundation's Research Centres of
Excellence programme, EOS and its field of research contributes greatly to NTU's
research strengths in Sustainability, which is one of the university's Five
Peaks of Excellence.
Story Source:
The above story is reprinted from materials provided by Nanyang Technological
University, via AlphaGalileo.
Journal Reference:
S. N. Sapkota, L. Bollinger, Y. Klinger, P. Tapponnier, Y. Gaudemer, D. Tiwari.
Primary surface ruptures of the great Himalayan earthquakes in 1934 and 1255.
Nature Geoscience, 2012; DOI: 10.1038/ngeo1669
https://www.sciencedaily.com/releases/2012/12/121228084026.htm
More Serious Earthquakes Predicted in the Himalayas