A new book on Indian earthquakes holds important lessons for our future

Partly in response to this, I wrote a long story for Lounge in July 2020 on the probability of a massive earthquake striking north India, especially the deadliest kind—a Himalayan earthquake. For the story I spoke with seismologist and earth scientist, C.P. Rajendran, who, along with his partner Kusala, also a seismologist, are two of the foremost authorities on earthquakes in the country.

While it is as yet impossible to predict when an earthquake is going to strike, it is possible to gain a probabilistic estimate of regions where a large earthquake is due—by studying the nature of faults running underneath in the Earth’s surface, allied with a knowledge of the history of earthquakes in that region. While explaining how tension builds up in a fault over a long time, and how that tension is inevitably bound to be released in the form of an earthquake, Rajendran used a memorable metaphor, that of banking. “It’s like you are putting money into your savings account and never taking it out. So, it gets accumulated,” he said. Someday, you will have to withdraw it.

Earlier this year, the two scientists published a book, The Rumbling Earth: The Story of Indian Earthquakes. A handbook of sorts, it is an extremely informative work that takes a whole-of-the-field approach to the story: From the birth of seismology and how the planet’s tectonic plates function, to detailed snapshots of South Asia’s various earthquake-prone regions, as well as a history of earthquakes in India. For the latter, the authors draw on their decades-long field work and research across India, bringing to life the geological stories behind some of South Asia’s most feared and infamous earthquakes.

When the authors received their education in earth sciences in the 1970s, they were among the first generation of seismologists to be trained in the wake of a discovery that had shocked and stunned the world—that of plate tectonics. Indeed, while reading the opening few chapters of the book, one is confronted with a remarkable fact: Before the late 1960s, the world at large hadn’t a clue that the Earth’s crust is made up of gigantic slabs of rock called tectonic plates that float about on a partially-molten layer of the planet’s mantle.

As the authors say, once this fact had been established, the field of seismology—the study of earthquakes—truly came into its own. What is very well understood is that most of highest magnitude earthquakes occur at the boundaries between two plates, because that is where the pressure is also at a maximum. As far as South Asia is concerned, the most earthquake-prone area is along the Himalayan Range, since that is where the Indian plate has been pushing against (and subducting under) the Eurasian plate, ever since they started colliding some 65 million years ago.

The authors devote a large part of the book to understanding the high seismic activity of the Himalaya, which has seen some of the most destructive earthquakes in recorded history, from the 1950 Assam-Arunachal Mw.8.2 quake to the 1934 Nepal-Bihar Mw.8.4 quake. The biggest takeaway from this discussion is how vulnerable the highly populous and haphazardly-developed Gangetic plains are to future mega-earthquakes, especially along a long stretch of about 700km along the central and western Himalaya, which the authors call the “central seismic gap”.

Roughly ranging from the Kishtwar area in Jammu to Pokhara in Nepal, while this region has seen many moderate earthquakes (which, like the Kangra earthquake of 1905, or the Gorkha earthquake of 2015, have nonetheless caused massive death and destruction), a mega earthquake of over Mw.8, where the very earth along the Gangetic plains may liquefy—like during the 1934 earthquake—is long overdue.

This comes up for discussion in the penultimate chapter of the book as well, where the authors discuss the complete lack of preparedness for mega earthquakes, and the extreme myopia of “development” projects comes in for a scathing critique. Writing specifically about Uttarakhand’s Char Dham highways project, the authors have this to say: “The 900km long, two lane highway…is deeply worrying from the point of disaster response and mitigation. Due to deforestation and road building, the steep slopes of soft rocks are bound to slide.” An additional hazard to the earthquake-prone Himalayan foothills is that of the rampant construction of “super dams”, whether in Uttarakhand or in Arunachal Pradesh.

The authors also tackle the history and future threats caused by tsunamis arising from major ocean earthquakes. In this regard, their telling of the story of the 2004 earthquake and tsunami is important. Equally illuminating is the discussion of earthquakes in the interior regions of India, far away from continental margins, where earthquakes are extremely rare, but where, like the disaster in Killari in Maharashtra in 1993, even a mild earthquake can cause extreme devastation.

Quite entertaining is the chapter on decoding the role played by earthquakes throughout India’s history, and how seismologists and archaeologists study both historical texts as well as structures to pinpoint the rumblings of medieval earthquakes, which, ultimately, allows scientists to identify the location and possible extent of future quakes.

Ultimately, The Rumbling Earth is a timely reminder that for all of our anthropocentric egotism, humans occupy a very precarious niche on an extremely huge planet which changes and moults its systems slowly, over millions of years. Every once in a while, when the Earth shrugs, we had better be prepared, or be faced with the prospect of the rug being pulled out, quite literally, from under our feet.