Mt Barker residents shaken but not scared by latest March earthquake, Geoscience Australia says that’s five in a row

Are the recent small Mount Barker earthquakes working up to something bigger? And is the area a quake hotspot? We ask Geoscience Australia the important questions.

Mount Barker’s locals say they’re not overly concerned after the latest earthquake, the fifth in a month.

A 2.9 magnitude quake was detected at a depth of 10km just after 7pm on Tuesday, according to Geoscience Australia.

The most recent quake had an epicentre near the Glenlea housing estate, about 1km from Aston Hills.

It follows a 3.7 magnitude earthquake at the Aston Hills housing estate on March 6 (and three smaller earthquakes in between),

But residents of the two estates said they were not regretting their decision to move in, and described the earthquakes as interesting rather than frightening.

Colin te Kempel, 39, and wife Sakura te Kempel, 33, who live at Aston Hills, said they heard both quakes, but had not regretted their decision to move in four years ago.

“The first one was bigger, this one felt like more of a shift, the rattling was stronger last time,” Mrs Te Kempel said.

“I’m not really concerned, I’m just interested really, it’s not something that’s really happened that frequently in Adelaide before.”

David Nitschke, manager of The Landing @ East Village, a cafe adjacent to the first quake’s epicentre at Aston Hills, said while he felt the first quake, he did not notice the most recent quake.

He also remarked on the closeness of the quakes as being “interesting”.

David Nitschke from The Landing @ East Village at Mt Barker. Picture: Keryn Stevens

“Definitely not expecting it to happen so close to the last one,” Mr Nitschke said.

“As close to each other as it was is interesting.”

Mr Nitchske said customers at his cafe appeared unfazed by the quake, and had not expressed concern.

A woman, who wished not to be named, said she would take a closer look over her home insurance policy for her Glenlea Estate townhouse following the second quake.

“I was thinking the other day I should check my insurance to make sure it’s covered for earthquakes,” she said.

“It felt like a big truck going by.”

Geoscience Australia senior seismologist Jonathan Bathgate told The Advertiser that within 30 minutes of the incident, 1400 ‘felt reports’ were received.

“This area of Australia really is probably one of the more active areas of the country,” he said.

Mr Bathgate said earthquakes were rarely singular events and often occurred in groups.

Another Aston Hills resident, who wished not to be named, said he found the quake “creepy”.

“It’s really weird it happened so close together,” the man said.

“I was shocked, really, it was a bit creepy, but I’m not massively concerned.”

The man said he moved in around a year ago, and felt both earthquakes.

The red dot shows the earthquake in Mount Barker on 29 March 2022. The white dots are all earthquakes in South Australia for the last ten years. Picture: Geoscience Australia

Q&A: Geoscience Australia senior seismologist Dr Jonathan Bathgate, explains the quakes to science journalist Clare Peddie.

Q: So we’ve had a series of these smaller earthquakes here now. Are we working up to something bigger?

A: It‘s hard to hard to say. Obviously, we can’t predict earthquakes. A search going back 12 months brings up five earthquakes that have all occurred this year in March, in the Mount Barker area. Starting with the magnitude 3.7 on the 6th of March, and then there was a small earthquake a couple of hours after that (2.4). Then 1.9 on the 7th, a 2.0 on the 9th and then 2.9 last night (29 March).

Q: Why is Mount Barker is a hotspot for earthquakes?

A: This region is one of the more active parts of the country. Through Adelaide, Mount Barker and into the Flinders is probably one of the more seismically active parts of Australia, the others being the Gippsland region in Victoria and southwest of Western Australia in the Wheatbelt region is also very active. So between those three probably accounts for the majority of earthquake activity that we see in Australia each year.

Q: It‘s been suggested there’s a mine near Mount Barker, would that have any bearing on this earthquake? Can mining activity trigger a quake?

A: It‘s possible, we have had things like that in other parts of the country. But you know, this area is very seismically active. I wouldn’t think that was a factor in this case at all, there’s nothing to lead me to believe that that’s the case. I haven’t looked at how far away the nearest mine is. But you know, it’s certainly not unusual for us to get earthquakes here dating back, you know, since we’ve been recording earthquakes. I don’t think there’s any mining aspect to these ones.

The felt reports from Tuesday night’s earthquake. Picture: Geoscience Australia

Q: Can earthquakes happen anywhere, or only on faultlines?

A: There are faultlines probably right across Australia that we have not mapped yet, and we don‘t know how active they are. So it is very likely that we will get earthquakes and regularly in places that we haven’t seen them occur before. And that’s partly just because we’ve only been monitoring for earthquakes in Australia for a very short period of time. And when you consider geological history, it’s even shorter. And so we get earthquakes occurring in areas that we we’ve never detected them before. And that was certainly the case with Australia’s largest earthquake that occurred in Tennant Creek in 1988. We had not recorded any seismic activity there, right up until that that happened. So there’s that unknown aspect of it just because we’re, we’re still learning.

Q: Does that mean we should be doing to prepare for something bigger?

A: Look, there‘s nothing to say that this sort of sequence of events is going to lead to anything larger. We can’t predict it. Everything we’ve seen so far really is consistent with earthquakes that we’ve seen in this region in the past. They’re all sort of small, but you know, there are active fault lines in the Adelaide region, so we know that they can host large earthquakes. In 1954 there was a magnitude 5.4 right in the centre of Adelaide, or very close to the city centre. That caused a lot of damage. So we do know that there is potential for larger earthquakes in the region.

For every earthquake that we have here, people are logging onto our website and filling in what we call a ‘felt report’ that tells us what they experienced, where they’re located, how they felt that earthquake, which helps us understand what how much shaking was associated with that earthquake and how we need to adapt our building codes to accommodate earthquakes in the region. So it all feeds into our seismic hazard map, which then sort of feeds into developing the building codes.

Q: How is it that one earthquake might sound or feel different to another?

A: It can vary significantly depending on where you are and how far away you are from the earthquake.

People in a house built on softer soils, as opposed to hard rock, will feel it differently. Those softer rocks may shake more, or amplify that shaking. So you tend to get that in large sedimentary basins where a whole area sort of shakes like jelly, as opposed to the hard rock where the seismic wave is transmitted very efficiently through that rock and you just get that large, quick, sharp jolt, and not a whole lot of shaking.

If somebody is on a on a higher level in a tower block, for example, they may experience more shaking than people on the lower floors.

There‘s also the size of the earthquake. These smaller earthquakes tend to just be a very short sharp jolt, or a loud boom and then not very much associated shaking, as opposed to some of the larger earthquakes where you get prolonged shaking that lasts for several seconds.

Also if it‘s a little bit deeper, they may not feel it as much as something that’s very shallow.

Q: Is there a threshold where people usually start to feel it?

A: At magnitude, two, or two and a half, if they‘re very close, they may feel something. But certainly when you get up into the threes it will be felt in a wider region, going out to 20 to 30 kilometres, but this one certainly has been felt at least 50 kilometres from the event going right up north and to the western edges of Adelaide and heading up towards Mount Pleasant. So it’s been certainly quite widely felt.

Q: Is there any advice you’d care to offer?

A: I think it‘s always good to take advantage of these events that are not particularly damaging or dangerous to remind people of what they should do if there is a large earthquake with a lot of shaking. Drop, cover and hold on is best practice. So don’t just try and run out of the out of the house, or out of the building while the shaking is happening. Because quite often, that’s where there’s a lot of debris that has fallen off the front of the building and when people run out of buildings like this debris lands on top of them. So the best advice is to drop to the ground yourself, before you get knocked over. Find something sturdy to hide under or cover yourself and hold on to it until the shaking stops and at that point, then move outside of the building – so that anything that has is going to fall off has already fallen off and the front of the building and you can you can get out safely. It’s quite rare for buildings to completely collapse. If the building you’re in sustains damage and if you’re under something sturdy, then you’re in a good position for someone to rescue you, or to get yourself out.