The Sikkim Earthquake is a prelude to bigger disasters. Constructing even concrete houses in the region is fraught with risks.
The Darjeeling-Sikkim Himalaya sits in a seismically high-risk zone. This was a fact that almost everyone in the hills has known fora while. However, there is no record of any great earthquake (less than7.0 Richter scale magnitude) in the history of the Darjeeling-SikkimHimalaya. This led to a sense ofcomplacency in the hills and urbanisation and development mushroomed. The “Ikra” Assam type houses gave way to “plainstype” flat- roofed multi-storeyed concrete houses that were more often than not built by slicing-up hill-slopes like “tosh-roti” (bread) or on precariously balanced stilts on hill slopes. Those who were aware shivered at the very thought of a great earthquake occurring in the Darjeeling-Sikkim Himalaya and collectively yelled from every available roof-top about the earthquake hazard and the associated disaster we were like to face.
This made sense till the mid 1990s when Global Positioning System (GPS) came along and changed the whole game. The Global Positioning System allows us to measure positions on the surface of the earth very accurately and also determine how much the point is getting displaced over time. This information gets translated into surface velocities that give us an insight into how the ground is moving even when earthquakes are not being recorded. GPS measurements tell us that India is moving like a car towards Northeast at about 5 cm/year and slamming into a wall-like Tibet in extreme slow-motion along the Himalayan boundary that decelerates it from 5 cm/year at Bangalore to 4.7 cm/year in North Sikkim; the Himalaya is the front end of this colliding and continuously crumpling car. The difference of 0.3 cm of motion is being absorbed into the Darjeeling-Sikkim Himalaya as strain energy every year since millions of years. The accumulated strain keeps getting released as earthquakes when it crosses a particular threshold determined by the strength of the rocks. Given this fact, not experiencing a great earthquake is not good news. It merely points to the fact that the strain that has gone into the Darjeeling-Sikkim Himalaya has not been released in a significant manner.
The good: There were a number of good things about this earthquake. First, its epicentre was located in the Kanchenjunga Range far away from populated regions and not in Mangan. So, the location of the epicentre was fortuitous. Second, the earthquake was a moderate 6.9. Not quite a great earthquake but, as Bharat Mani Pradhan put it, “Powerful enough to shake us and hopefully stir us into some action”. The third good thing about this earthquake was that it was a strike-slip earthquake which is basically similar to the motion of rubbing your hands when held vertically. In terms of the colliding car, it was not a new crumple developing in its front end but just a big scrape on its side during the process of frontal head-on collision.
The bad: It is obviously the confirmation of our worst fears and the resultant death and destruction that was caused by the earthquake.
The ugly!: This has to be the realisation that we are grossly under prepared to tackle a calamity that would descend upon us if a great earthquake with an epicentre in the Teesta Valley would strike us. Also, it confirms what GPS results are telling; the Darjeeling-Sikkim Himalaya is continuously getting strained and it is only a matter of time before we get a great earthquake. The ugly truth of the situation is that we cannot predict earthquakes in human time-scales because the processes in the earth operate in a super-slow mode spread over millions of years. However, science is letting us know that we are overdue for a great earthquake in our space. The other ugly part of the situation is that a vast majority of us have already committed our lifetime’s savings into constructing the spacious and “pucca” RCC dream houses. Can we financially afford to abandon the houses that we have built even after the realisation that we may be living in buildings that may end up being tombs? Like it or not, we have to make very tough personal decisions. We have to decide if we want to risk it all and continue to live in our RCC houses and hope that we can find a “triangular space of life” in our collapsed concrete structures when the big ones strikes. A real “Ram Bharose” or “whatever will be, will be” existence as Wing Commander Prafulla Rao put it. The other choice is to cut our losses and go back to not having concrete over our heads. That is the tough and ugly personal choice each and every one of us will have to make. The least we can do is to not build any new concrete over our heads and keep the earthquake hazard in mind when making decisions on all future developmental activities in the Darjeeling-Sikkim Himalaya. We owe it to each and every person who had to sacrifice their lives on September 18, 2011 to give us this wake-up call and this lesson. This has to be the lasting legacy of this tragic event and the best way to pay our respects to those who were taken away from us on September 18, 2011.
- Published in the Editorial of Bengal Post (04Oct2011)
Dr Malay Mukul is an ex-student of
Dr Graham’s Homes, Kalimpong & is presently
Department of Earth Sciences,