ADOPT SCIENTIFIC TECHNIQUES TO QUAKE-PROOF BUILDINGS

First Words The April 28 earthquake of magnitude 6.4 on the Richter scale not shook Assam and the northeast, it exposed the vulnerability of the region to such major quakes and threw up several questions on various fronts. Such powerful was the quake that the earth cracked near its epicentre in the Sonitpur district in Assam.

Not just the land, but walls and ceilings of people’s houses scores of miles in the radius also cracked and buildings swayed like betel nut trees in the wind. In Guwahati's GS Road area, due to the impact of the quake, the bathroom floor of a building collapsed and it fell in the bedroom of the floor below. A portion of a hill at Bogamati, located near the Indo-Bhutan border in the Baksa district, also broke. Water seeped out of the paddy field as well. From April 28 till June first week, around 100 aftershocks have also been recorded in the region- some of over magnitude 4.5.

The entire northeast region is categorised under seismic zone 5- this means that the region is extremely prone to high-intensity earthquakes. The April 28 tremor occurred near the Kopili Fault, close to the Himalayan Frontal Thrust (HFT) which is a seismically very active area “associated with collisional tectonics where Indian plane sub-ducts beneath the Eurasian Plate”. It may be mentioned here that a fault is a fracture or zone of fractures between two blocks of rocks. Faults allow the blocks to move relative to each other. The Kopili fault is a 300 km northwest-southeast trending fault from the Bhutan Himalaya to the Burmese arc.

Earthquakes are not uncommon in the northeast region and according to the National Centre for Seismology (NCS), the region has seen several moderate to high-intensity earthquakes. One of the worst among them was the great Assam-Tibet earthquake in 1950 which measured 8.6 magnitude on the Richter scale. Approximately 4,800 people were killed as a result, and several landslides blocked the tributaries of the Brahmaputra and changed the topography of the region. The 1869 Cachar earthquake, measuring 7.4 magnitude, was another major seismic activity to hit the region.