The 1897 Great Assam Earthquake

Looking back at the quake that shook my hometown 127 years ago

The summer of 1897

After days of rain, the sun shone through the beautiful hills of Shillong in the northeastern corner of India on the fateful Saturday, the 12th of June, 1897. Sir Henry Cotton, the erstwhile Chief Commissioner of Assam during the colonial government in India, was occupied with finalizing all preparations for the Diamond Jubilee celebration of Queen Victoria¹. Taking the benefit of the sunny afternoon, Mr. Cotton took out the two-wheeled horse-drawn vehicle to ride with his wife, who just returned from a few weeks in England. Before he could get full control of the harness for the horse, it galloped through the windy roads, kicking up dust clouds behind them. What accompanied the dust clouds were rattling sounds from the crumbling guardhouse, cracking sounds of the roads splitting wide open, howling wind whipping through the pine trees, and pouring of pine cones as if they replaced the rains from the past few days. As Mr. Cotton somehow stopped the uncontrollable horse and rescued his wife from the cart, he looked back at their big, elegant Assam-type government house. He could see nothing but crumbles and red dust from the mortar. Amidst the chaos of crumbling buildings and shattered roads, Shillong bore the scars of the Great Assam earthquake that struck on that fateful Saturday, the 12th of June, 1897, leaving behind a scene of devastation and despair.

The Government Bungalow in Shillong before and after the Great Assam Earthquake in 1897 [Source: Home and Indian Memories by Henry Cotton]

Documentation of impacts from the earthquake

Geological Survey of India’s Calcutta (now Kolkata) office was occupied following the earthquake, with Thomas Henry Digges La Touche at the helm of affairs in the absence of the Acting Director, Richard Dixon Oldham. Oldham was traveling in Nainital in Northern India for other official purposes. A day-to-day narrative of the chaos and impacts following the earthquake could be inferred from a series of letters that La Touche wrote to his wife Nancy², who was in Shimla. These letters were being sent from Calcutta, where La Touche was stationed, and reported widespread damage in the buildings, including the hotel where he lived. La Touche, in fact, sent a paper to Nature with the observations of the earthquake calling it “The Calcutta Earthquake,” because of his biased experience from Calcutta, without realizing that Shillong, a few hundred kilometers east, was the epicenter and at the heart of all the wreckage that the earthquake caused. The letters from La Touche to his wife reveal a narrative of ingenuity amidst the chaos, as La Touche recorded seismograms with a rudimentary instrument that he made with pieces of tin, a suspended boulder, a glass bead, and a bamboo needle that scratched a glass plate. These letters also document the post-earthquake investigation that La Touche undertook from Calcutta to Sylhet (now a city in Bangladesh) through various towns in the Brahmaputra valley, Shillong, and Cherrapunji.

The route that LaTouche traversed for documenting earthquake damages followed by the 1897 earthquake [Source: Ambraseys and Bilham (2003)]

After returning from Nainital, apart from sending a group of geologists Oldham embarked on a journey through the epicentral areas of what is now the Indian state of Meghalaya, meticulously documenting his observations of the aftermath of the devastating 1897 earthquake³. Oldham’s memoir, which encapsulates the observations from this big earthquake, is considered a seminal work for its observations and insights despite the nascent understanding of the subject at that time. This memoir is the basis of the scientific debate through the last century about the earthquake's source, time, and mechanisms that still persist 127 years later. Although all of the documentation by the imperial government seemed to be detailed, at least in terms of scientific observations of damage and ground deformation, it does not provide any documentation on the impacts on the native population or casualties therein. The contributions of the native population were appreciated only as they pertained to keeping the imperial flag held high in government offices.

Scientific debates about the earthquake

In his memoir, Oldham provided a contour map of the epicentral region based on the field measurements by his team of geologists and himself. Oldham concluded that the rupture occurred on the Chedrang Fault, northwest of the Shillong Plateau. However, the reality is that with the resources and technology of the day, the team could not have completed a thorough reconnaissance in a fraction of the region that was actually impacted. Moreover, these reports were strictly limited to observations of physical deformation on the earth’s surface. It does not provide any insights into the impacts on the people and their property. Oldham mentions that this focus area selection intentionally avoided “sensitization” and only adhered to scientific observations. Impacts on the people were also not documented appropriately by the newspapers and media organizations of the day, occupied with the Diamond Jubilee celebration of Queen Victoria that Sir Cotton was preparing for in Shillong before the earthquake hit.

Epicentral region of the 1897 earthquake as inferred by Oldham in his 1899 memoir, where the dashed rectangle indicate the suggested source rupture

However, the passage of time and the evolution of seismological techniques have unveiled critical insights about this earthquake in the past century. Scientific debates about the earthquake's magnitude, location, and intensity have continued. Only in the last two decades has a general consensus been reached about these topics. This includes the discovery of an earthquake fault, separate from what Oldham had reported in his memoir. This newly discovered fault has been named Oldham Fault in recognition of his contribution, which played an instrumental role in the discovery⁴.

Additionally, the earthquake’s magnitude was originally calculated to be 8.7 on the Richter scale, an obsolete scale to measure earthquakes outside of California for which it was designed. Reassessment of the earthquake magnitude using modern methods to use the limited information from the earthquake puts it at around 8.1 on the moment magnitude scale⁵, a standard scale used to express earthquake magnitude. Despite limited data from the earthquake, much progress has been made in understanding the rupture that caused the earthquake, which can help prepare these regions for big future earthquakes.

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How things have changed since then

So many things have changed since then, and so many are history-defining!

India gained independence in 1947, 50 years following the Great Earthquake. The northeastern part of the country was divided into multiple states, with the capital of Assam relocated to Dispur in Guwahati, whereas Shillong became the capital of Meghalaya state [as indicated in the map below]. Guwahati became the hotspot for economic activities in Northeastern India throughout the 20th century. Shillong became a connoisseur for tourists and witnessed significant infrastructure development. Although estimates of the population in the region from 1897 are difficult to obtain, it is fair to say that it has grown multi-fold. Based on an estimate of the population in Guwahati from 1901, around one-third of the entire population of Assam (78,845 square kilometers) from 1901 (~ 32 lacs or 3.2 million) now lives only in the city of Guwahati (216 square kilometers). More people migrating to urbanized areas like Guwahati and Shillong means denser neighborhoods with the construction of buildings and other infrastructure systems such as power, roads, water, etc.

Map of northeastern India [Source: www.mapsofindia.com]

What has not changed, however, is the potential of an earthquake from the same sources in the future. Going back to the concept of hazard and exposure, as discussed in the previous essay, hazard has not changed - but the exposure to this hazard has significantly changed. What it means is that if the same earthquake is to occur today and shaking occurs in the exact same region, significantly more people will be affected just by virtue of growth in population and density of infrastructure.

Fortunately, one aspect that has drastically changed since then is technology. Today, quite accurate ground shaking estimates are shared publicly within minutes of the earthquake occurrence; a few parts of the world are employing (or planning to employ) early warning systems to provide a few seconds of notice to switch off critical infrastructure to avoid major disruption; computer simulation enables understanding the potential impact of earthquakes which can help design mitigation actions to reduce risks preemptively, among many other advancements.

Looking Ahead

Technological advances allow us to learn more about earthquake sources in the region and simulate the consequence of potential future earthquake events on the community and the built environment. These insights allow us to identify the most vulnerable aspects of our community and design risk mitigation actions preemptively to prepare ourselves for future catastrophes. These insights allow the decision-makers to plan and invest in risk-reduction activities, such as drafting policies to strengthen (retrofit) existing vulnerable and critical buildings, developing risk transfer mechanisms via earthquake insurance, creating awareness among our communities, and improving construction and operation practices for future infrastructure.

As a native of Guwahati myself, and having familial ties in Shillong and thereby spending significant time there, I have witnessed tremendous changes in the built environment and socio-economics of the region in the past couple of decades. If not done carefully, these changes can increase risk in the region rather than reduce it. Therefore, risk-informed decision-making is essential to enhance the resilience of cities like Guwahati and Shillong so that they are better prepared to withstand a future big earthquake than they did 127 years ago.

1. Home and Indian Memories by Henry Cotton

2. Tom La Touche and the Great Assam Earthquake of 12 June 1897: Letters from the Epicenter by Roger Bilham

3. Report on the great earthquake of 12 June 1897. Memoirs of the Geological Society of India by R.D. Oldham

4. Plateau pop-up in the 1897 Assam earthquake, Nature 410 by Roger Bilham and Philip England

5. Reevaluated Intensities for the Great Assam Earthquake of 12 June 1897, Shillong, India by Nicolas Ambraseys and Roger Bilham