US Geological Survey says equipment in Beijing often picks up mining
blasts but not explosions, and estimates the Tianjin blasts as magnitude
2 or 3
An explosion in China
that killed at least seven people and injured hundreds more was
registered by the US Geological Survey as two small seismological
actions followed by one big one at a seismometer station 160km (100
miles) away in Beijing.
The USGS equipment is meant to detect seismological activity like
earthquakes, but also frequently picks up activity from mining blasts.
USGS geophysicist John Bellini said it is rare to detect
seismological activity from other events, like the explosion in Tianjin.
“Blasts that are not mine-related are rare to record, just because they
don’t get transferred into the ground very well,” he said.
don’t get transferred into the ground very well,” he said.
Bellini
said that it looks like multiple blasts were recorded at the Beijing
monitoring facility, but the agency is not completely certain that the
activity came from the explosion in Tianjin. The nature of the blast
means that the seismological monitor does not give a completely accurate
assessment of the explosion’s magnitude, he said.
“I can’t really give you an accurate magnitude picture – because it
is one station and I don’t know how much air blast and how much of it is
ground vibration, so I can’t give any precise magnitude measure for
it,” Bellini said.
He did say that a safe estimate for the explosion is that it registered between a magnitude 2 and 3 on the Richter scale.
“That doesn’t accurately portray the amount of energy in the
explosion, just because it isn’t transferred to the ground very well,”
said Bellini.
Citing the verified Weibo account of the China
Earthquake Networks Centre, AFP reported the magnitude of the first
explosion was the equivalent of detonating three tons of TNT, while the
second was the equivalent of detonating 21 tons of the explosive.
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