Seismic Shockwaves in Tibet Trigger Avalanches and Raise GLOF Risks for Bhutanese Communities

The 7.1 magnitude earthquake that struck the Shingtse region of Tibet, China, on January 7 has sent shockwaves beyond the borders of its epicenter, triggering avalanches in the Lunana area of Bhutan. Two significant avalanches descended from the Table Mountain above the Bechung Glacier, but fortunately for local communities, the gentle slope of the glacier effectively absorbed the impact, preventing the snow and ice from reaching the Bechung Glacial Lake. Despite this fortunate outcome, experts warn that such seismic events pose a continual threat of Glacial Lake Outburst Floods (GLOFs). Phuntsho Tshering, an executive glaciologist with the National Centre for Hydrology and Meteorology (NCHM), underscored the risk, stating, "The vibrations destabilise glaciers, triggering avalanches." He noted that while the immediate danger was mitigated, Bechung Glacier Lake is rapidly forming, raising concerns about its ability to withstand the accumulating mass over time. The earthquake's tremors were felt across Bhutan, particularly in Gasa, the nearest dzongkhag to the epicenter, which recorded a maximum intensity of four on the Modified Mercalli Intensity (MMI) scale. The scale measures how strongly people feel the tremors, with Gasa experiencing notable vibrations. Other regions of Bhutan reported milder effects, with intensity levels ranging between zero and three, and areas in western Bhutan registering a peak intensity of two. In response to the earthquake's occurrence, communities in Lunana were promptly alerted, and NCHM personnel, alongside a team from their headquarters, were dispatched to assess the situation at various glacial lakes. Fortunately, reports indicated that no major disturbances were observed at Thorthomi, Rapstreng, and Bechung glacial lakes. However, minor moraine slides on the inner moraine walls of the Thorthomi-Rapstreng barrier were noted, raising alarms about the integrity of this critical infrastructure that has been deteriorating over the years. A collapse of the moraine dam could have catastrophic consequences, including the potential release of approximately 53 million cubic meters of water from the Thorthomi and Rapstreng lakes in a worst-case scenario. Due to the continuous threat posed by Thorthomi Lake, which has been flagged as the most dangerous in the region, the NCHM has been actively advocating for the permanent relocation of residents in the nearby villages of Thangza and Tenchoe to safer elevations further away from the risk zone. The planned relocations to higher grounds such as Damthangkha, Bayza-Gangjuk, and Dungbiteng have been ongoing since last year. As the NCHM team continues to monitor the glacial lakes, they have urged downstream communities to maintain vigilance against potential GLOFs, a risk that grows with each seismic activity in the region. On a broader scale, the Department of Geology and Mines is collaborating with the GovTech Agency to enhance Bhutan's earthquake monitoring systems, aiming for completion by the end of March. This upgrade will feature a web-based platform providing real-time earthquake intensity information, enabling residents to report their experiences and enhancing overall safety protocols. While the recent events highlight the growing challenges posed by climate change and geological instability in the region, the resilience of communities and the proactive measures being taken offer a glimmer of hope in navigating these risks. The collaboration between experts and local agencies seeks not only to mitigate immediate dangers but also to ensure the long-term safety and sustainability of the affected areas as they face the ongoing impacts of a changing environment.