Residents of a South Australian community are hoping for an end to the low magnitude aftershocks that are rumbling through the region thanks to upwards pressure on tectonic plates. 

Since April 13, 11 earthquakes have been recorded in and around Jamestown, south of the Flinders Ranges, including a 4.2 magnitude earthquake last week that shook houses and cracked walls. 

Aftershocks between 1.6 and 2.3 magnitude have rattled the town since last Wednesday.  

Jamestown resident and manager of the local newsletter, Tracey Dewell, said she had been on edge since the first earthquake and during subsequent “unnerving” aftershocks.

“I’ve been here for 20 years, I’ve never experienced an earthquake that large,” she said.

“This one was really quite a quick, sharp noise and then a rumble afterwards, so the damage had already happened before you actually realised that the there was an earthquake.”

Moving Australian Plate

Geoscience Australia senior seismologist Jonathan Bathgate said the Flinders Ranges region was one of the “more active” parts of Australia, due to the movement of tectonic plates. 

“There are a number of faults that run through the Flinders region” Mr Bathgate said.

“The Flinders Ranges is thought to be actively uplifting due to the the stresses that the Australian crust is under in that area.” 

He said the Australian Plate was moving about seven centimetres north every year which caused stress to build up at the boundaries. 

“That stress is transmitted away from the plate boundary into the crustal rocks within the plate,” he said.

“That stress builds up to a point where it gives way along local fault lines, such as this one.

“Occasionally, the fault locks up and we get this sudden larger release and that results in a larger earthquake.” 

Australia typically experiences about 100 magnitude three or higher earthquakes every year.

Most occur across the Flinders Ranges in South Australia, Gippsland in Victoria and southern Western Australia.;

Jamestown is located at the foot of the Southern Flinders Ranges and is home to about 1500 people. (ABC North and West: Isabella Carbone)

No hard or fast rule about aftershocks 

Ms Dewell’s house was damaged during the 4.2 magnitude earthquake last week.

The ceiling cornice fell into the lounge room, missing her daughter in the room at the time.

She says she is holding off on claiming insurance while the aftershocks continue. 

Other residents have reported various cracks and minor structural damage to buildings.

Ms Dewell said residents were worried about what was going to happen next.

“If it would just stop, it would be lovely, but Mother Nature doesn’t want to give us a break just yet.”

Unfortunately, for those that call Jamestown home, it’s not clear when the aftershocks will abate. 

“There’s no hard and fast rule for how long a sequence can continue for,” Mr Bathgate said. 

“Generally what happens is they [earthquakes] become less frequent and the magnitudes reduce over time, but it certainly can vary from each individual earthquake sequence.”

Seismological Association of Australia member David Love said there was also no established way to predict earthquakes. 

“If it feels like it’s going to be strong, drop down, get under a table and hang on,” he said.

Posted , updated