Research: After the massive Nepal earthquake in 2015 that claimed lives and destroyed properties, seismologists have begun ask if the region where Bhutan is located is perhaps the only segment of the Himalayas that has not experienced a major earthquake over the past half millennia.
This has now been clarified by a study using historical information and paleoseismological observations. “We are able for the first time to say, yes, Bhutan is really seismogenic, and not a quiet place in the Himalayas”, said György Hetényi, a Geophysicist at the University of Lausanne, who led the team of researchers.
Bhutanese historian Karma Phuntsho collaborated with the seismologists and the team has published an article in Geophysical Research Letters, which constrains the location and the magnitude of the earthquake in 1714.
According to the study, Bhutan experienced a major earthquake on May 4, 1714 (20th of the 3rd Bhutanese month) of between 7.5 and 8.5 magnitudes in central and western Bhutan. The findings were based on Bhutanese biographies, Assamese records and geologic studies.
The earthquake took place when the ninth Je Khenpo Shakya Rinchen was four years old. The earthquake killed his mother but young Shakya Rinchen, who lay cuddled on his mother’s lap, was dug out of the debris. He went on to become one of Bhutan’s most illustrious writers and religious figures and wrote about the earthquake in his books. His successor, the 10th Je Khenpo Tenzin Chogyal also records how the new Gangteng temple built by Tenzin Lekpai Dhondup was reduced to rubble in the spring of 1714.
“The earth shook about thirty times that day alone and the aftershocks continued for about a month,” Karma Phuntsho said, citing the historical sources. “People across the country were struck with fear and the young ruler of Bhutan, Chogley Namgyal, had to sleep in a tent outside the dzongs in Thimphu and Punakha. It is thanks to such biographical and historical writings in Bhutanese archives that scientists, who have some geological evidence for the earthquake, are today able to narrow down the location, time and the magnitude of the earthquake.”
The researchers added that the life-cycle of earthquakes is much longer than the human life cycle and people forget about them unless there are reliable written records. “The lack of knowledge of the past hampers our resilience and efforts in preparation for such hazards in the future,” Karma Phuntsho said.
The multidisciplinary study concludes that the entire Himalayan Arc (some 2,400kms) can produce large earthquakes and Bhutan is prone to large earthquakes in the future.
The proposed seismic gap in Bhutan, according to their findings, is in fact just an information gap.
“This will help properly assess earthquake hazards in the Bhutanese Himalaya,” György Hetényi said.
The article can be accessed online with the title ‘Joint approach combining damage and paleoseismology observations constraints the 1714A.D. Bhutan earthquake at magnitude 8 ± 0.5.’