A major earthquake of magnitude 6.8 (M6.8) struck the north of Myanmar (Burma) in the early hours of Sunday 11 November.
The mainshock, which occurred 72 miles north of the city of Mandalay, was followed by three aftershocks of between M5.0- M5.8.
At least 12 people have been reported killed, while the United States Geological Survey’s Pager alert system indicated a 50% chance that up to a hundred lives might be lost.
Tectonic Setting of Myanmar
Myanmar’s location at the boundary of the Indian and Eurasian plates makes it vulnerable to seismic events: earthquakes are by no means uncommon.
The relatively rapid northwards movement of the Indian subcontinent means the two plates are converging at a rate of around 40-50mm per year.
To the south, the tectonic setting becomes even more destructive as the Indian plate is subducted beneath the islands of Java and Sumatra.
Convergence of this nature leads to mountain-building on a large scale and the surface expression of this collision includes some of the world’s major mountain ranges, including the Himalayas and the Karakoram mountains, as well as the high Tibetan Plateau. In Myanmar the overall direction of convergence is oblique rather than direct, leading to a broad and complex belt of faulting and folding where convergent and transform margins lie parallel. Seismic activity in the area is characterised by both strike-slip (lateral) and reverse movement, with numerous shallow earthquakes.
Earthquakes in the East of the Himalayan Arc
Given the complex relationship between the two plates, and the enormous forces at work, it is unsurprising that earthquakes in this setting are common. A map of seismicity in the area since 1990 clearly shows a scattering of shallow earthquakes, usually of relatively small magnitude, running parallel to the collision zone.
The USGS doesn’t publish a list of historic earth tremors for Myanmar, but in March 2011 a tremor of M6.9 close to the border with China is reported to have killed at least 74 people, and in 1975 a tremor of M6.5 caused extensive damage in central Myanmar. Further back, the USGS notes in its summary of regional tectonics that severe damage was caused in the country as a result of a series of 6 earthquakes with magnitudes of at least M7.0 – the series of quakes are reported to have cost at least 610 lives.
Although Myanmar may not seem the most obvious candidate for an earthquake prone nation, its location, squeezed between the collision zone of the Himalayas and the highly seismically active subduction zone beneath Indonesia (which has been the source of some of the world’s largest and most destructive quakes) means that there is always a risk of destructive – and fatal – tremors.
BBC News online. Burma earthquake: at least 10 feared dead. (2012). Accessed November 11, 2012.
USGS. Seismotectonics of the Himalaya and vicinity. (2012). Accessed November 11, 2012.
USGS. Magnitude 6.9 Myanmar. (2012). Accessed November 11, 2012.
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