CANBERRA, ACT, Aug. 21 -- Geoscience Australia issued the following news release:
Aftershocks are possible
A magnitude 5.6 earthquake hit south eastern Queensland at 9.49 AM on Saturday 16 August, near the town of Kilkivan and around 40 kilometres west of Gympie.
The earthquake was widely felt across the east coast of Australia, with over 24,000 felt reports registered.
Seismologist Dr Michelle Salmon said that the earthquake was felt as far south as Wollongong and as far north as Cairns.
Why was the earthquake felt as widely as it was?
"This is the largest onshore earthquake in Queensland in over fifty years," she said.
"Queensland is Australia's least seismically active state," Dr Salmon added. "In the past 12 months we have only recorded 10 earthquakes in the whole state, with the most recent large quake being the magnitude 4.5 that occurred in Townsville in March this year."
This earthquake was a similar magnitude to the 1989 Newcastle earthquake, but it caused much less damage.
"A higher magnitude earthquake doesn't necessarily mean that there will be more damage," Dr Salmon said. "It depends on many factors including local geology, local population density, and building design."
"This earthquake was in a less highly populated area than the Newcastle quake and building standards have improved over time. It was also further from the town. These factors make damage less likely."
While earthquakes of this size are less common in Australia, no area is completely immune from earthquakes.
"Moderate to large earthquakes can occur anywhere across the continent, and without warning. On average, Australia experiences an earthquake of this size once every year or two," Dr Salmon said.
She also advised that it would be reasonable to expect aftershocks following this earthquake.
"We identified three very small aftershocks after the main shock but they were so small that we couldn't get accurate information about them," she added.
Aftershocks are smaller than the mainshock and generally become smaller and less frequent with time. "However, it is important to note that it is not possible to predict precisely when or how large these earthquakes may be, or when the sequence will diminish to a point where they are no longer detectable," Dr Salmon said.
To study the seismic profile of the area in detail, Geoscience Australia has sent six temporary earthquake monitoring equipment to the area where the earthquake occurred.
"These rapid deployment kits give us specific information about seismic activity in these areas, allowing us to study these events in more detail," Dr Salmon explained.
"This data informs our national seismic hazard models and can be used by local and state governments and emergency management agencies to inform responses to earthquakes in the future."
Dr Salmon added that this data is important to help deepen our understanding on how earthquakes occur in Australia.
"Australia isn't near a tectonic plate boundary, so our earthquakes don't occur due to tectonic plates slipping past each other, but rather as a result of stress from the boundaries being transferred into our continental crust," she said.
The Australian plate is the fastest moving continental land mass on Earth and is colliding into the Pacific plate to the north and east, and the Eurasian Plate to the northwest.
"This generates compressive stress in the interior of the Australian continent. Earthquakes are caused by the sudden release of this stress when rocks deep underground break and move along a fault line."
"When an earthquake occurs, no matter how large or small, we always ask people to lodge a 'felt report' on our website," Dr Salmon said. "This gives us more information about how the energy travels through the earth and is a useful input to our National Seismic Hazard Assessment.
"We are grateful to the 24,000 plus people who lodged felt reports because all this data is valuable."
A number of people in the area of this earthquake reported that they didn't feel it, even though people in nearby streets did.
What causes some people to feel a quake and others not?
"People in the same area experience earthquakes differently depending their sensitivity and what they are doing at the time," Dr Salmon said.
"Chances are if you are driving or running around you won't feel it but if you are sitting down quietly you will."
Earthquakes can and do occur anywhere and at any time. Geoscience Australia works with governments, industry and communities to help reduce the impact of disasters on our country, and to help build more resilient communities now and in the future.
To protect yourself during an earthquake, the best advice is to drop, cover and hold on. First, drop to your hands and knees, bend over to protect your vital organs, and protect your head and neck with your hands. If you can, find something sturdy to shelter under, such as a desk or table, and hold on by gripping a table leg or other part of your sturdy shelter.
If you felt the earthquake, please complete a felt report at https://earthquakes.ga.gov.au.
Disclaimer: Curated by HT Syndication.
