MANDALAY – More than 1,600 people have been killed in Myanmar and thousands more injured following a 7.7 magnitude earthquake that was also felt in neighboring countries.
Hundreds are believed to be trapped under the rubble of collapsed buildings – including at least 50 construction workers who are unaccounted for after a high-rise was flattened by the earthquake in Bangkok.
More than 90 people are believed trapped in the rubble of an apartment block in Mandalay, Myanmar, a Red Cross official tells AFP.
A rescue team in Mandalay tells the BBC: “We are digging people out with our bare hands”
Myanmar is considered to be one of the most geologically “active” areas in the world because it sits on top of the convergence of four of these tectonic plates – the Eurasian plate, the Indian plate, the Sunda plate and the Burma microplate.
The Himalayas were formed by the Indian plate colliding with the Eurasian plate, and the 2004 Tsunami as a result of the Indian plate moving beneath the Burma microplate.
Dr. Rebecca Bell, a reader in tectonics at Imperial College London, said that to accommodate all of this motion, faults – cracks in the rock – form which allow tectonic plates to “slither” sideways.
There is a major fault called the Sagaing fault, which cuts right through Myanmar north to south and is more than 1,200km long.
Early data suggests that the movement that caused Friday’s 7.7-magnitude earthquake was a “strike-slip” – where two blocks move horizontally along each other.
This aligns with the movement typical of the Sagaing fault.
As the plates move past each other, they can become stuck, building friction until it is suddenly released and the earth shifts, causing an earthquake.
Mandalay was much closer to where the ground slipped and would have experienced significantly more severe shaking than Bangkok.
Although Myanmar regularly experiences earthquakes, Dr Ian Watkinson, a lecturer in earth sciences at Royal Holloway University, thought it was unlikely that many buildings were constructed to be earthquake-proof.
“General poverty, major political upheaval, alongside other disasters – e.g. the Indian Ocean tsunami in 2004 – has distracted the country from concentrating on the unpredictable risks from earthquakes,” he said.
“This means that, in many cases, building design codes are not enforced, and construction happens in areas that could be prone to enhanced seismic risk, for example flood plains and steep slopes.”
Parts of Mandalay and its buildings also lie along the floodplain of the Ayerwaddy River. This makes them very vulnerable to a process called liquefaction.
This happens when the soil has a high water content, and the shaking causes the sediment to lose its strength and behave like a liquid. This increases the risk of landslides and building collapses, as the ground can no longer hold them up.
Dr. So warned that there was “always a chance” of further damage to buildings near a fault line due to aftershocks – tremors that follow an earthquake, which can be caused by the sudden transfer of energy into nearby rock.
“Most of the time aftershocks are smaller than the main shock, and tend to decrease in size and frequency over time,” she said. (BBC)
