Author: Pallava Bagla
Publication: The Indian Express
Date: March 19, 2001
A quick and seemingly comprehensive
scientific analysis on the recent Bhuj quake concludes that it was the
"deadliest intraplate earthquake" in recent times. The first scientific
analysis of its kind on the devastating Republic Day quake appears in the
latest issue of prestigious American journal Science and calls it a 'rare'
phenomenon while pleading that a stricter implementation of the existing
building codes "could have substantially reduced the damage'.
India's renowned Earth scientist
Harsh K Gupta and three of his colleagues from the National Geophysical
Research Institute in Hyderabad, review the January 26 earthquake in the
Kutch region of India - on the pages of Science which is estimated to have
cost at least 30,000 lives and economic loses of about $10 billion. The
earthquake was of the rare "intraplate" variety, in which the fault runs
through the interior of a tectonic plate, rather than along its edge. Most
earthquakes like those in the Himalayan region take place because the large
Indian plate is constantly being pushed under the giant Eurasian plate
and once sufficient tension builds up on the folds and faults it is released
in the form of earthquake.
Unlike these Himalayan or the even
the Californian earthquakes, the Bhuj quake happened in area where there
are fractures in the same plate itself in this case the Indian plate. Earthquakes
well within a plate itself are few and far between and hence the scientists
are calling the Bhuj quake a 'rare event' since such intraplate earthquakes
account for less 0.5 per cent of all global seismicity says the scientists.
The authors also point out that
much of the property damage could have been avoided if the building codes
for the zone predicted to have the highest seismic potential had been implemented.
They say relatively simple methods are also available for protecting houses
in rural areas. Because further prediction of earthquakes will probably
not occur in the foreseeable future, according to the authors, seismic
risk maps and appropriate hazard-reduction strategies are essential throughout
India.
The first full and serious scientific
analysis of the devastating quake, which according to some killed over
50,000 people, calls it a magnitude 8 earthquake. It also suggests that
the epicenter is located 15 km northwest of Bhachau, and 60 km east of
Bhuj. They say as expected in such a huge temblor 'damage in river floodplains
was much worse than in hard rock areas'.
In a surprising revelation the 4-member
team says "in Anjar, Bhachau, Gandhidham and Ahmedabad, multi-storied Buildings
sank up to one floor into the ground, possibly due to a quicksand like
effect in dry sandy soil areas".
The earthquake also caused widespread
liquefaction in the Great Rann saline marshy lowlands possibly the cause
of the large surface water that emerged after the earthquake. Gupta and
his team recommends a quick plan of action for the "retrofitting" of important
buildings to make them quake resistant by using existing "in-expensive
methods to strengthen old dwelling units" could help mitigate the problems
posed by earthquakes.
