Geoscience Australia has deployed three earthquake monitoring systems in and around Muswelbrook in the Upper Hunter in recent weeks. Experts hope these systems will provide valuable insight into the cause of a series of tremors that have shaken the region since August 23 and improve the accuracy of the institution's data.
Residents around the region were shaken by another tremor in the early hours of Saturday morning, September 7, following a litany of quakes that began with the most significant tremor in 20 years late last month.
Earthquake seismologists from Geoscience Australia - the federal body that monitors seismic activity - Melbourne's Seismology Research Centre and the University of Sydney have broadly indicated over recent weeks that while the cause of the quakes can be attributed to several factors, the string of tremors that have shaken the region are connected, sharing a similar magnitude, epicentre and estimated depth.
Trevor Allen, an earthquake seismologist at Geoscience Australia, told the Newcastle Herald on Saturday that while it is well established that the continent is under seismic stress - the gradual accumulation which eventually causes the rock of the earth's crust to break along fault lines causing earthquakes - it is relatively rare for Australians to experience the strong ground movement that residents of the Hunter have felt over previous weeks.
The federal government research body hopes that the three temporary monitoring devices will record instrumental data on the Muswellbrook events that will not only improve the accuracy of Geoscience Australia's recording but provide valuable insight to improved building codes and the threat earthquakes may pose.
The body's nearest permanent monitoring station to Muswellbrook is more than 100 kilometres from the supposed epicentre of the weekend's activity near Mt Arthur coal mine, Dr Allen said, the distance of which necessarily leads to some uncertainty about the potential depth and proximity of the epicentre relative to the BHP mining operation.
While the reported depth of Saturday's significant tremor around 6am was around five kilometres, Dr Allen said it was likely shallower than that, given the readings from the data.
Coal mining, among other human activities, has been linked to earthquake activity in other parts of Australia and worldwide. Still, experts broadly say that it is difficult to draw an unequivocal or direct link between the events over the past three weeks and mining.
While evidence suggests that the removal of vast amounts of rock through mining contributes to and changes the stresses in the crust that lead to earthquakes, several factors contribute to the eventual release and fault that leads to tremors.
Dr Allen said Geoscience Australia had recorded as many as six tremors in the area leading up to the 4.5 magnitude quake that was felt around 6am and said that given the series of earthquakes over recent weeks, there was an increasing likelihood that more would follow. He said there was a much lower chance of a more significant quake, though smaller aftershocks were more likely. Generally, experts expect that the tremors should diminish.
