The ACT can expect aftershocks from this morning’s earthquake, but it’s unlikely people will feel them.
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Seismology professors from the ANU predict this morning’s magnitude 3.7 tremor will trigger smaller quakes in the vicinity of magnitude 2 for up to two weeks.
Professor Brian Kennett, who has been studying and mapping earthquakes in the ACT since 1984, said only those standing directly above the aftershocks would be likely to feel them.
“The stress regime shows that the whole of the southeast coast is being squashed a little bit,” professor Kennett said.
“There’s quite a lot going on but the chance (of further activity) is finite. There might be some more twos, for a week or two at most.”
This morning’s tremor was recorded on seismographs up to 300km away and felt by people up to 46km away.
Professor Kennett and fellow seismology expert at ANU Professor Malcolm Sambridge said earthquake activity could be unpredictable.
The Canberra area, on average, experiences a minor earthquake every year.
The last of similar magnitude was a 4.2 in 1998. There was also a 4.5 recorded at Gunning in 1994.
“There are hundreds of them up there,” Professor Kennett said.
“There was one lady whose house was right on top of them. I think she’s moved now. The whole area is quite interesting. There are a lot of faults.”
Professor Kennett recalled a tremor at Glenloch Interchange in 1985 – of “3-ish” magnitude – which knocked books off the shelves at ANU.
There was another 3.1 tremor at Uriarra Crossing in 1979, and a similar size earthquake recorded in Murrumbateman in the early 1970s, and a cluster of smaller earthquakes in the area, also in the 1970s.
Melrose High School, Daramalan College and a separate seismometer in a vault at Mt Stromlo have been included in a national program for schools to host seismometers, called Australian Seismometers in Schools. Each of those recorded this morning’s tremor.
Professor Kennett said data showed that this morning’s earthquake was quite shallow. This meant impact of the tremor would be confined to a small, localised area. This morning’s physical break – the part of the earth which actually moved - was likely to have been confined to between 100m and 200m, he said.
Faults which occur deeper into the Earth’s surface often impact a larger area.
Both professors agreed that while there could be minor aftershocks, it was highly unlikely that the magnitude of tremors would increase.
