Destruction and Transformation: Lessons learned from the 2015 Gorkha, Nepal, earthquake

By Surya Narayan Shrestha (National Society for Earthquake Technology, Kathmandu, Nepal) and Susan E. Hough (U.S. Geological Survey, Pasadena, California. USA)
 

Citation: Narayan Shrestha, S. and Hough, S.E., 2025, Destruction and Transformation: Lessons learned from the 2015 Gorkha, Nepal, earthquake, Temblor, http://doi.org/10.32858/temblor.363
 

On the afternoon of Saturday, April 25, 2015, central Nepal was rocked by a massive earthquake that initiated near the Gorkha district west of Kathmandu Valley. Dubbed the Gorkha earthquake, the name pays homage both to the district and to Gorkha (or Gurkha) warriors, known for fearless military prowess (Gregory Groth, U.S. Department of State, oral communication, 2015). The 2015 earthquake was the largest temblor to strike Nepal in over 80 years (Adhikari et al., 2015), with moment magnitude estimated between 7.8 and 7.9 (USGS, 2017; ISC, 2015). The north-dipping fault-break at depth ruptured toward the east, generating a ribbon of severe shaking and damage at the surface.

Powerful shaking hit the densely populated Kathmandu Valley, which lies near the southern, shallow edge of the rupture at depth. Seismic waves were trapped and amplified by old lake-bed sediments underlying the valley (Dixit et al., 2015). Those relatively long-period waves took an especially heavy toll on taller buildings and vulnerable old construction.
 

 

As Nepal’s residents and government struggled to assess the situation and conduct recovery operations, seismologists on the other side of the planet awakened to the news that worst fears may have been realized — an earthquake approaching magnitude 8. International Earth science professionals had identified Nepal — and the Kathmandu Valley in particular — as among the regions at risk of a mega-disaster, with a deadly combination of high earthquake hazard, dense population, and vulnerable construction (Dixit et al., 2013; also see Chaulagain et al, 2016).

Images filtering out of Nepal revealed stark scenes, including catastrophic damage to some of Kathmandu’s most storied cultural heritage sites (for example, Figure 1). The earthquake was caught in the act not only by modern seismic instruments — including seismometers, accelerometers, and GPS stations — but also by CCTV cameras that showed Kathmandu being slammed back and forth as if the valley were a snow globe in the hand of a malevolent giant. Information and photographs trickled in from more remote villages where the earthquake had taken a tragic toll on vulnerable masonry buildings.

Ten years after that fateful day, to discuss the impacts of this earthquake and what the future may bring, we first briefly consider features of the country itself. This includes where and how people live, past seismic events and societal memories of these quakes, and how Nepal’s approach to seismic hazard mitigation has evolved. Only then can we consider a vital question: how can Nepal chart a course to a safer future?
 

A country of collision

When people think of Nepal, they mostly think of mountains, which is to say, the snow-capped peaks of the Himalayan range, home to trekking trails and villages scattered across the mountainsides. The Kathmandu Valley, a former lakebed zone, is nestled within the Himalayan foothills, close enough to the High Himalaya to afford glimpses of high peaks on clear days.

The majority of the most densely populated regions in Nepal are actually clusters in the lesser-known Terai, the fertile plains below the mountain ranges in the southern part of the country. In the High Himalaya and adjacent foothills, people tend to concentrate in valleys. In the mountainous part of the country, however, the Kathmandu Valley is by far the biggest population center, with an estimated population over 3 million (Chaulagain et al., 2016).

Kathmandu has long beckoned to adventurous tourists who are drawn to a rich cultural heritage and the gateway to trekking opportunities. In the minds of many westerners, the name Kathmandu ranks alongside Shangri La and Xanadu — mystical faraway places. But Kathmandu is real. The million or so visitors who visit Kathmandu every year find something less than Shangri La, with temples and other cultural heritage sites surrounded by a traffic-choked landscape of urban sprawl. Relatively modern structures, mostly one to five stories high, carpet the valley. In recent years a few high-rise structures, taller than five stories, have also sprung up.

The Kathmandu Valley, along with the rest of Nepal, has come of age with awareness of earthquake hazard. Local lore holds that Nepal’s king died in a large earthquake in 1255 (Sapkota et al., 2012). More recently Nepal was rocked by an earthquake in 1934 that claimed over 15,000 lives and caused heavy damage in both India and Nepal (Sapkota et al., 2012). That earthquake spurred changes, with a recommendation from the Geological Survey of India that people in Nepal build short, simple structures while avoiding especially vulnerable brick, mud, or stone-rubble construction. For a time, new construction respected recommended height limits, rarely exceeding two or three stories.

Over time, memories of the 1934 disaster faded among the population, even as awareness of earthquake hazards grew among earthquake professionals within and outside Nepal. The plate tectonics revolution in the 1960s and 1970s provides a scientific framework to understand Nepal’s precarious situation (e.g., Ni and Barazangi, 1984; Bilham, 2019): The Indian subcontinent is being pushed under Eurasia at a rate of about 5 centimeters (2 inches) per year. Nepal is a small country, perched in a saddle riding atop one of the most dangerous plate boundaries in the world — the highly active collision zone between the massive Indian and Eurasian plates (Figure 2).
 

 

Nepal’s earthquake professionals

Nepal’s community of earthquake professionals continued to work toward risk reduction, even as memories of the 1934 disaster faded. A moderately damaging earthquake in southeast Nepal in 1988 was a turning point for earthquake risk reduction and preparedness activities in the country (Yadav et al., 1994).

The National Building Code of Nepal was developed in the early 1990s, largely informed by the lessons from the 1988 earthquake (Yadav et al., 1994). For the first time, a formal seismic hazard assessment was done as part of building code development. Since then, the scientific and professional communities of Nepal have undertaken numerous projects to better understand seismic hazard and mitigate risks. But this community has struggled with limited resources to monitor earthquakes, assess earthquake hazards, and, critically, to serve as advocates with local officials, stakeholders, and the public.

In 1993, the Nepali non-governmental organization NSET, the National Society for Earthquake Technology, was founded to advance earthquake safety. Drawing support from the international community, NSET focused on appropriate and practical solutions, such as reinforcing some school buildings and training local builders on construction techniques that improve resilience. Other important efforts have included initiation of public awareness campaigns on earthquake safety; sensitization of policy and decision makers on ways of promoting earthquake-safe construction; emergency response capacity enhancement programs; and promotion of community level earthquake preparedness.

In 1999, with engagement of local earthquake professionals including NSET, Nepal launched an Annual Earthquake Safety Day in commemoration of the 1934 earthquake. Every year, the anniversary date provides an opportunity for outreach and education with remarkable involvement of communities, earthquake professionals, and policy makers.

The 2015 Gorkha earthquake took a tragic toll on Nepal, killing nearly 9,000 people and leaving many more homeless. To some extent, damage in the Kathmandu Valley was limited by lake-bed sediments that amplified shaking at some frequencies, but absorbed energy that would have been damaging to small ordinary buildings — those built according to local practices (Dixit et al., 2015). But without the preceding decades of work to reduce earthquake risk, the toll could have been far worse. Countries around the world continue to learn this lesson: investments in risk mitigation pay dividends, reducing both loss of life and economic damage when large earthquakes inevitably strike.

Much of the population of Nepal practices Hinduism or Buddhism. Traditional beliefs of both religions hold that destruction is an integral part of creation, which can be associated with earthquake experience (Subedi and Hetényi, 2021). Indeed, throughout recent history, damaging earthquakes have spurred risk reduction efforts in a number of countries, and the Gorkha earthquake was no exception. The international community, including individuals and agencies that had long-standing relationships with Nepali earthquake professionals, rushed to both help collect data and provide support to local professionals.

Investigations of large earthquakes in Nepal have important lessons for global earthquake science and risk reduction; within Nepal, the Gorkha earthquake was a direct catalyst for change. The Nepali government took key steps to advance the organized reconstruction and recovery efforts by creating the National Reconstruction Authority. In 2019, the National Disaster Risk Reduction and Management Authority was established to lead the disaster risk management efforts (Kanal, 2020).
 

Assessing Nepal’s seismic risk

In any country, risk reduction is a process. The process leads to improved construction of new buildings and broadly improved resilience of existing structures and infrastructure. But the process begins with science to characterize the hazard. What potential earthquake shaking is a place up against? Since the 1960s, the scientific community has been distilling best-available science into hazard maps cast in terms of earthquake probabilities, mapping out the level of shaking expected in different regions (Cornell, 1968).

During the building code development process in the years leading up to and after the Gorkha earthquake, earthquake professionals in Nepal began more organized and comprehensive seismic hazard evaluation work, co-led by Nepali professionals working with international partners (e.g., Stevens et al., 2018). Over time, and spurred by the Gorkha earthquake, hazard assessment was increasingly undertaken by Nepali professionals from a number of local organizations: the Department of Mines and Geology, NSET, and universities (e.g., Rajaure, 2019). Numerous maps were generated (see Rajaure et al., 2019), all similarly painting a swath of high hazard across Nepal, but with differences that mattered for building standards.

Assessing the level of shaking expected across Nepal is not an easy problem to confront. But even harder is the problem of translating hazard maps into actions that reduce risk. Such actions include establishing building codes and standards, and creating mechanisms to enforce them. For this part of the process to work, local earthquake professionals play a critical advocacy role, working with local officials and stakeholders. With earthquake professionals in many countries — including Nepal— scattered among different organizations, effective risk reduction requires that hazard maps be developed as a consensus product involving close partnership with stakeholders, including the private sector. These maps must reflect the current state of knowledge.

During the decade that followed Gorkha, professionals from Nepali organizations and institutions worked to improve hazard maps and establish a framework to develop a national hazard map, led by the Department of Mines and Geology, via a collaborative process. This effort is ongoing, involving regular engagement and dialogue among the professional community through annual meetings, conferences, symposia, and trainings that nurture a culture of consensus. Such dialogues have been facilitated regularly by agencies including the Department of Mines and Geology, the Nepal Geological Society, Khwopa Engineering College, the Seismology at School program, and NSET.

Contributions from the international scientific community, including the U.S. Geological Survey (USGS), Global Earthquake Model Foundation, and several universities and research organizations, have helped to foster a stronger environment for co-working, co-learning, and co-development of hazard understanding and products. The international community has provided guidance along the way. For example, the seismic network (Adhikari et al., 2015) has long been supported by the French government, and the USGS has provided technical training, assistance with earthquake monitoring, and strategic planning drawn from lessons learned in the United States.
 

The future of earthquake science and risk reduction in Nepal

Memories of earthquakes always fade. In southern California, nearly half the population was either not born or very young when the last major earthquake (Northridge) struck that region in 1994. In another 20 years, memories of Gorkha will be similarly dimmed among the local population. It falls to the community of local earthquake professionals to continue their work behind the scenes, a brick-by-brick process to keep the population safe when the next big earthquake strikes.

The 2015 Gorkha earthquake spurred these efforts not only with its tragic demonstration of the power of earthquakes, but also a stark realization: as massive as Gorkha was, only a thin sliver of the plate boundary at depth beneath the Himalayan range had ruptured (e.g., McNamara et al., 2017).

For Nepal, a magnitude 8 earthquake is not the Big One. Much larger earthquakes, breaking the plate boundary all the way to the surface, have happened in the past (Sapkota et al., 2012). Estimating the magnitude of these past events is difficult, but scientists fear that major Himalaya earthquakes could reach magnitude 8.5, if not higher (e.g., Sapkota et al., 2012; Bilham, 2019). The community of earthquake professionals in Nepal remains dedicated to advancing risk reduction, understanding that earthquakes far worse than Gorkha are not just possible — they’re inevitable.

From the experience of countries such as the United States, Japan, New Zealand and several earthquake prone countries in Europe and Latin America, it is very much clear that enhancing awareness and knowledge of earthquake phenomena and advancing risk reduction requires persistence and dedication. This is a long-term process. In Nepal, the Gorkha earthquake re-energized that process, but much work remains.

Lessons learned in the international community can guide the process of risk reduction in Nepal. And lessons learned from a major earthquake anywhere in the world continue to guide risk reduction and earthquake science everywhere.

April 25, 2015 was a dark day for Nepal. With its combination of high hazard and vulnerable construction, Nepal continues to face high seismic risk, with a daunting prospect of future losses of both lives and structures. In any country, risk reduction is a long-term process. Progress can seem painfully slow for professionals who dedicate their lives to improving societal resilience. By spurring the development of hazard assessment and risk reduction efforts, and the development of local capacities, lessons learned over the decade following the Gorkha earthquake have pushed that process forward.
 

Science Editor: Dr. Alka Tripathy-Lang, Ph.D.
Reviewer: Dr. Shiba Subedi, Ph.D.
 

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