“When the Himalayas Tremble: Seismic Memory, Myth, and the Rising Earthquake Risk in India" Science-Forward / Policy-Serious- Parag Biswas

The Himalayas have captivated humanity for millennia as much for its majestic peaks, serene valleys, and rich cultural heritage, as for the devastating earthquakes that inspired awe, curiosity, and sometimes even superstitions among its residents due to the uncanny relation between the biggest tremors in the region and some epoch-making events of Indian history and festivals in the country.

Mystics point out that Lord Curzon declared the First Partition of Bengal just four months after the largest earthquake in the Himalayan history on June 6, 1905, measuring 8.9 on the Richter scale; the biggest earthquake in the eastern Himalayas, measuring 8.6 on the Richter scale, occurred exactly three years after the independence of India on August 15 , 1950; and one of the deadliest earthquakes of the current century, measuring 6.9 on the Richter scale occurred on September 18, 2011 in the Himalayas in Nepal, Sikkim and north Bengal during the Vishwakarma puja, which is a Hindu festival dedicated to Lord Vishwakarma, the divine craftsman, who is regarded as the “architect of the universe.”

Mysticism apart, there has always been a fear of earthquakes among the residents of the hills and the foothills of the Himalayas as well as many far-off places in India and its neighbouring countries, who were significantly affected due to the catastrophic earthquakes in the Himalayas.

The age-old fear turned into panic on November 28 last year, when the entire Himalayan arc was for the first time placed in a newly introduced highest-risk Zone VI in the updated seismic zonation map as part of the revised Earthquake Design Code by the Bureau of Indian Standards.

The news of the new seismic zonation, in which the Sikkim-Darjeeling region was for the past time upgraded to the highest seismic risk Zone VI, spread like wildfire in the region.

Reams were written and hours were spent by the regional media analyzing the significance of the upgradation.

But as public memory is proverbially short, the thought of a devastating earthquake rocking the region was slowly ebbing from the minds of the residents by the first week of February this year, when the first of a series of earthquakes rocked Sikkim at precisely 1:09 am IST on February 5.

Starting from the midnight tremor, Sikkim was jolted 33 times in a span of 13 hours, and though the magnitude of the quakes was 4.5 and less on the Richter scale, the tremors reminded the residents of the vulnerability of the Sikkim-Darjeeling stretch of the Himalayas to heightened seismic activities over the past few years and cautioned them about a massive earthquake that may hit the region soon.

The Himalayan belt was earlier split between Zones IV and V, as the risks from long-unruptured fault segments in the Himalayas, particularly in the central Himalayas, was underestimated by seismologists since no major surface-rupturing event was recorded here in nearly two hundred years.

But as the risk from future earthquakes has increased due to the frequent tremors and the burgeoning population and an ever-expanding urbanization in the region, the Himalayas, which sit directly on one of the most active tectonic collision boundaries on Earth, have now been placed in the country's highest seismic risk zone.

The main seismic threat in the Himalayas stems mainly from the collision between the Indian Tectonic Plate and the Eurasian Plate that created the mountains about 50 to 60 million years ago.

The collision is still driving the Himalayas upward as the Indian Plate is continuously pushing northward into the Eurasian Plate at about five centimetres per year. The persistent movement of the plates is continuously building an enormous pressure within the Earth's crust, and whenever the pressure gets released suddenly, it leads to a powerful quake.

As the Himalayas are geologically young, the rocks in the mountains are still adjusting, folding and breaking, making the region more vulnerable to seismic threats.

The presence of several major fault systems beneath the range, namely the Main Frontal Thrust, Main Boundary Thrust and Main Central Thrust, each of which are capable of generating large earthquakes, has aggravated the threat.

The recent identification of long seismic gaps, where no major earthquakes for centuries have occurred, has increased the fear of a dangerous quake in the region as it suggests that there is a significant amount of energy stored beneath the Earth’s crust here, which is restless to get released.

The residents and the authorities should, therefore, work hand in hand to ensure that minimum fatality and economic damage is caused due to a major earthquake in the region.

The authorities must take immediate steps to ensure that stricter standards for buildings, bridges, and urban projects are adopted by the planners and engineers in the region; the disaster preparedness machinery is jacked up on an emergency basis; the retrofitting of infrastructure is urgently done; the expansions on soft sediments or active faults are stopped immediately; and the stipulated seismic standards are sincerely and honestly followed.

E.O.M.

paragbiswas1972@gmail.com