SINGAPORE, March 28 (Reuters) – A powerful earthquake of
magnitude 7.7 centred in the Sagaing region near the Myanmar
city of Mandalay caused extensive damage in that country and
also shook neighbouring Thailand on Friday.
HOW VULNERABLE IS MYANMAR TO EARTHQUAKES?
Myanmar lies on the boundary between two tectonic plates and
is one of the world’s most seismically active countries,
although large and destructive earthquakes have been relatively
rare in the Sagaing region.
“The plate boundary between the India Plate and Eurasia
Plate runs approximately north-south, cutting through the middle
of the country,” said Joanna Faure Walker, a professor and
earthquake expert at University College London.
She said the plates move past each other horizontally at
different speeds. While this causes “strike slip” quakes that
are normally less powerful than those seen in “subduction zones”
like Sumatra, where one plate slides under another, they can
still reach magnitudes of 7 to 8.
WHY WAS FRIDAY’S QUAKE SO DAMAGING?
Sagaing has been hit by several quakes in recent years, with
a 6.8 magnitude event causing at least 26 deaths and dozens of
injuries in late 2012.
But Friday’s event was “probably the biggest” to hit
Myanmar’s mainland in three quarters of a century, said Bill
McGuire, another earthquake expert at UCL.
Roger Musson, honorary research fellow at the British
Geological Survey, told Reuters that the shallow depth of the
quake meant the damage would be more severe. The quake’s
epicentre was at a depth of just 10 km (6.2 miles), according to
the United States Geological Survey.
“This is very damaging because it has occurred at a shallow
depth, so the shockwaves are not dissipated as they go from the
focus of the earthquake up to the surface. The buildings
received the full force of the shaking.”
“It’s important not to be focused on epicentres because the
seismic waves don’t radiate out from the epicentre – they
radiate out from the whole line of the fault,” he added.
HOW PREPARED WAS MYANMAR?
The USGS Earthquake Hazards Program said on Friday that
fatalities could be between 10,000 and 100,000 people, and the
economic impact could be as high as 70% of Myanmar’s GDP.
Musson said such forecasts are based on data from past
earthquakes and on Myanmar’s size, location and overall quake
readiness.
The relative rarity of large seismic events in the Sagaing
region – which is close to heavily populated Mandalay – means
that infrastructure had not been built to withstand them. That
means the damage could end up being far worse.
Musson said that the last major quake to hit the region was
in 1956, and homes are unlikely to have been built to withstand
seismic forces as powerful as those that hit on Friday.
“Most of the seismicity in Myanmar is further to the west
whereas this is running down the centre of the country,” he
said.
(Reporting by David Stanway
Editing by Frances Kerry)
