Kolkata: Located at the northernmost tip of northeast Indian, Arunachal Pradesh, was fortunately, shielded from major impacts of the deadly Manipur earthquake because of its geography and geology, said experts, cautioning against complacency. They say lessons must be learnt from the disaster to build site-specific quake-resilient structures.
Famous for its biodiversity, Arunachal Pradesh, sharing international borders with Myanmar, China and Bhutan, was perhaps the least affected when a 6.7-magnitude temblor along the Indo-Myanmar border jolted India’s northeast and east and neighbours Myanmar, Bhutan and Bangladesh.
At least eight people were killed and more than 120 injured in the Manipur temblor that affected its other northeast sisters including Assam, Meghalaya, Tripura, Sikkim and Nagaland. A six-storey under-construction building toppled in Manipur’s capital Imphal where the iconic Mothers’ Market also took a hit.
“Arunachal was outside a 50 km radius range from the epicentre at Manipur’s Tamenglong region. In addition, the geology in Arunachal Pradesh is different,” B.K. Rastogi, former director general of Gandhinagar-based Institute of Seismological Research (ISR) told IANS.
The soil in Manipur’s quake-hot areas is alluvial which magnified the seismic waves, but most of Arunachal is rocky which doesn’t have similar amplification effects, explained Rastogi.
Common principles of geography and energy distribution played a key role in the state escaping the disaster.
“As the distance from the epicenter increases there is an equal decrease in the energy released and subsequently a decrease in the effect.
“This is one of the factors why Arunachal Pradesh did not see damage during the Monday’s quake,” Gibji Nimasow, a professor in the geography department of the Rajiv Gandhi University, Arunachal Pradesh, told IANS.
Manipur bore the brunt of the temblor, which struck at 4.35 am and left a trail of devastation in the region: at least four people were injured in southern Assam, walls of some residences and other buildings cracked in Tripura, Mizoram and Nagaland where the intensity was strong.
IIT-Guwahati’s Chandan Mahanta pointed out the quake was distinguishable from other temblors in the region because of its duration (more than 30-plus seconds) but Arunachal, home to the great Indian hornbills, was lucky time-wise too.
“While the first quake was only for a second in Arunachal Pradesh, the second quake on Monday lasted for few seconds, less than a minute, which saved the state from disaster,” Nimasow elaborated.
While the magnitude of the tremor was 6.7 in Manipur and Assam, it slumped below 6 in Arunachal, said Nimasow.
“The potential to cause damage was low as the temblor’s intensity was less,” disaster management coordinator for UNDP project Sarat Das, told IANS, from Tripura, adding the quake was classified as a moderate intensity one.
According to the USGS, moderate to large earthquakes in the region around northeast India, where the subcontinent collides with the Eurasia plate, are fairly common.
India’s northeast region is considered the world’s sixth most earthquake-prone belt.
In the last 100 years, some 19 other quakes greater than magnitude-6 have occurred within a 250 km range from the site of Monday’s temblor. The largest was a magnitude-8 quake in 1946.
But northeast India has not learnt its lessons yet despite its vulnerability, lamented Durgesh C Rai, of IIT-Kanpur’s National Information Centre of Earthquake Engineering.
“Copying building designs from other cities for modernisation is not right. Buildings in earthquake prone regions should be according to the site-specific codes,” Rai told IANS.