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On March 28, a devastating earthquake of magnitude 7.7 struck Mandalay, Myanmar, resulting in significant destruction across Myanmar and neighboring regions, particularly Thailand. Recent reports have confirmed more than 5,000 casualties. At the Annual Meeting of the Seismological Society of America, researchers presented preliminary findings regarding the earthquake’s mechanisms, the resulting ground shaking, and the damage inflicted on infrastructure.
Understanding the Rupture
Myanmar sits at a tectonically active juncture where the Indian and Eurasian plates converge. The earthquake produced a substantial rupture of over 400 kilometers along the Sagaing fault, which serves as the primary lateral plate boundary in the region, as explained by U.S. Geological Survey seismologist Susan Hough.
This event represents one of the most extensive surface ruptures documented worldwide, according to researcher Nadine Reitman from USGS. Historical data indicates that the Sagaing fault has experienced numerous significant earthquakes exceeding magnitude 6 in the last century; however, prior to March, no magnitude 7 earthquake had occurred in the vicinity since 1839, Reitman noted.
The rupture displayed “supershear” characteristics, meaning it propagated faster than the speed of sound after an initial delay, which is typical for large strike-slip earthquakes, as highlighted by Zhigang Peng of Georgia Institute of Technology. Following the earthquake, there has been a notable uptick in seismic activity recorded in Thailand and China’s Yunnan and Guangdong provinces, implying widespread seismic triggering due to the dynamic stress from the mainshock in Myanmar.
Severe Ground Shaking
The earthquake generated intense shaking that affected areas up to 100 kilometers from the rupture site, impacting regions such as Mandalay, Sagaing, Nay Pyi Taw, Bago, and Shan State, according to Hough. She mentioned that the Department of Meteorology and Hydrology in Nay Pyi Taw, responsible for managing Myanmar’s national seismic network, suffered considerable damage from the shaking.
Shake maps produced from the quake by Chung-Han Chan of the National Central University in Taiwan suggest that areas along the rupture experienced Modified Mercalli Intensity values surpassing VIII. Such intensity levels indicate severe shaking that complicates standing, can displace heavy furniture, and inflicts damage on structures lacking seismic resilience.
Additionally, research presented by Hiroshi Kawase from the General Building Research Corporation in Japan focused on local site conditions, a study they have been conducting since 2014 to better understand ground motion in Sagaing and Yangon along the Sagaing fault.
Data from Sky and Sea
Utilizing satellite imagery, researchers led by Xuechun Li of Johns Hopkins University successfully created a city-scale map of the earthquake’s impact in Mandalay within days of the event. Their innovative approach suggests substantial potential for rapid damage assessment after disasters.
Moreover, this earthquake marked a milestone as it was the first large-magnitude quake detected through a novel system of telecommunication submarine cables repurposed into over 100 seismic sensors, a development reported by Mikael Mazur from Nokia Bell Labs at the SSA meeting.
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