The earthquake on February 6 followed by a severe aftershock of almost equal magnitude in southeastern Turkey and Syria devastated several towns with tragic consequences.
The source zone of these earthquakes lies at the intersection of three tectonic plates: the Anatolian, the Arabian, and the African plates. The relative northward motion of the Arabian plate pushes the Anatolian plate west, creating two strike-slip faults: places where two plates are sliding past each other as they move horizontally.
The shallow focus of the earthquake – which happened when a strike-slip fault moved more suddenly than usual – and the fault’s location close to population centres were responsible for the resulting destruction.
Flimsy buildings
Almost the entire building stock of the region was razed to the ground within seconds, killing more than 4000 people. It will be decades before communities in the affected regions – including in Syria, a country already ravaged by a violent civil war and mass migration – can return to normal, provided the civil strife and military activities don’t hamper reconstruction efforts.
Also read: The world’s deadliest earthquakes since 2000
Two other factors contributed to the quake’s severity: it occurred in the early hours, when people were asleep, and the buildings offered poor resistance the shaking.
This isn’t the first time a big earthquake has occurred in this region. In 1138 AD, an earthquake with a deadly sequence of aftershocks was reported from near the border town of Aleppo in northern Syria, not far from the recent earthquake source. Given this history, the authorities should have built earthquake-resistant buildings in the region. But this didn’t even happen in the quake-affected area in Turkey, which has been politically and administratively more stable, is unclear.
In fact, while the Turkey-Syria earthquake triggered the devastation, it wasn’t responsible for it; the blame for that lies with the flimsy buildings. The experience should motivate us to thoroughly review India’s own quake preparedness considering poor enforcement of zoning and construction rules is ubiquitous in the country.
Seismic gaps
The Indian terrain is prone to great earthquakes, more so since the political boundaries of our country roughly follow the tectonic divides in the west, the north and the east. One of our major concerns now should be the 2,500-km-long Himalayan plate boundary, which extends from the northwest to the northeast, in a zone with the potential for large quakes (magnitude 7 and above).
Scientists are aware of identifiable gaps along the Himalayan axis where the historical release of geological tension doesn’t fully account for the strain that has built up. For instance, the Central Himalaya has been historically deficient in earthquakes compared to other areas. So it’s one region that can reasonably be expected to generate a large earthquake in the future.
The northeast Himalaya also hosts such seismic gaps. How prepared are we to face the consequences in future in these areas? The Indian government has also been enthusiastic about building new dams at the foothills of the Himalaya along the country’s northern border. Are we also ready for landslip-impounded dams and the consequent sudden flooding on the downstream side?
The sole historical example of a large earthquake in the Central Himalaya dates to 1803 (although there were two smaller events in the 1990s), with an estimated magnitude of 7.5-7.9. It triggered landslides that smothered entire villages in the hills, liquefied the soil in distant areas and further accelerated ground motion in the Ganga alluvial plains, including around Delhi. The casualties then were in the thousands. What if a similar quake occurred today?
According to an estimate in 2000, based on the 1991 Census, economic data and assuming all the 1.8 million houses in the region lack earthquake-resistance provisions, if an earthquake like the 1905 Kangra earthquake (magnitude 7.8) were to occur today in the Himalaya, the direct losses would be Rs 5,100 crore, around 65,000 lives, and 4 lakh houses.
The fact is we know how to build houses and other buildings that won’t kill people in an earthquake. We just don’t build such structures in earthquake-prone areas, according to the seismic code, especially since the government is in an urbanisation and industrialisation frenzy.
Today, as a first step, we need to undertake a comprehensive study of the vulnerability of buildings and structures in different places to different earthquake intensities. One big challenge here is to ensure all new construction (especially in places with the highest quake risk) can resist shaking and that all existing buildings are protected by retrofitting. Put another way, we need ways to make these activities more cost-effective. Such an endeavour requires systematic, long-term efforts.
Note also that India follows a variety of building practices. In most of the country, both construction style and the quality of construction materials vary according to one’s income. In areas where traditional structures are more common, we need to bolster traditional earthquake resistance methods.
Free flow of information
The trend in annual losses from disasters has been markedly upward, and appears to be related to the greater exposure of more people and infrastructure to natural disasters and the attendant increase in risk. One of the underlying reasons is an increase in the aerial extent of habitation in vulnerable areas. So we must overhaul town and municipal planning by-laws to accommodate hazard-safety measures using the existing appropriate building codes, developed with the Bureau of Indian Standards.
Equally importantly, we need to develop an environmental land zonation scheme for both urban and rural areas and strictly adhere to its recommendations during planning and construction.
Finally, how do we translate our detailed scientific knowledge on earthquake safety to the level of implementation? This is why translating such knowledge into a format that is easily available, accessible, and actionable is essential.
In fact, real-time data dissemination should become a norm in all fields. Free data-sharing is the backbone of any knowledge-based society. A gag order – like the one the National Disaster Management Authority recently implemented in response to the Joshimath disaster – will inevitably be self-defeating. Such clumsy processes might also dampen the spirit and momentum of science–policy engagement and the free flow of information to the people.
We have a long way to go towards integrating development with disaster mitigation strategies, including grassroots community-based initiatives. The Turkey event reminds us that, most of all, we shouldn’t be caught unaware when the next major earthquake strikes.
C.P. Rajendran is an adjunct professor at the National Institute of Advanced Studies, Bengaluru, and author of a forthcoming book, ‘The Rumbling Earth: The Story of Indian Earthquakes’, by Penguin.
Published - February 08, 2023 02:43 pm IST
