Super Pit linked to quake cause
Kalgoorlie's massive Super Pit may have triggered the magnitude 5 earthquake that shook Boulder on Tuesday morning, damaging historic buildings and shutting the town's central business district.
A former seismologist with Geoscience Australia, Victor Dent, said mining in the area might have triggered the quake.
Mr Dent, an honorary research associate in geology at the University of WA, said the quake's epicentre was very close to the Super Pit and there was a good chance it had been triggered by stresses caused by the pit.
"When you take a big pile of rocks out of the ground, you change the stress patterns in all the rocks around it," he said. "There are hundreds of earthquakes in Australia every year and all you can say is that they are caused by stress.
"I think the stress was changed by the digging of the Super Pit and that predisposed the area to an earthquake."
Earthquake Engineering Society president and Australian Seismological Centre director Kevin McCue said there had been much seismic activity in the area during the 1940s and 1950s that had been attributed to mining.
"But the jury is still out and I would need to see more data before I could be sure it was definitely mining," Mr McCue said.
Geoscience Australia senior seismologist David Jepsen said whether the mine contributed was not known and it would take weeks to determine the exact cause.
"There is no one theory that we can say is correct about what caused the quake at this stage," Dr Jepsen said.
He said earthquakes in Australia were usually caused by stress from the movement of the plates or gravitational load.
Dr Jepsen said Geoscience Australia had put sensors in the area of the quake and was monitoring aftershocks. It was studying satellite data to detect minute deformations in the earth's surface.
"There is no firm evidence that this quake was mine-induced, but you can't rule out the contribution the mine may have had." Johan Wesseloo, from the Australian Centre for Geomechanics, said it was "unlikely the quake had been triggered by the Superpit".
Dr Rick Rogerson, from Geological Survey WA, said he understood the quake had happened well below the surface and was simply caused by normal tectonic activity.
A spokesman for KCGM, operators of the Super Pit, said the company did not want to comment on speculation the mine might have caused the quake.
