A joint research effort funded by City of Moreton Bay Council is digging into the secrets surrounding an ancient earthquake that shaped the landscape thousands of years ago.
Researchers from The University of Melbourne have unveiled the size and scope of the earthquake along a fault line west of Caboolture, which exceeded magnitude 6.5 at some stage in the last 20,000 to 35,000 years.
Following identification of the fault by Geoscience Australia, Council initiated a Queensland-first project which saw University of Melbourne researchers use Light Detection and Ranging (LiDAR) mapping to determine the location of past large earthquake surface ruptures and through that, the most likely locations of future ruptures.
Excavations were then undertaken to obtain sediment samples at different locations along a break in the ground caused by the earthquake, known as a scarp, late last year.
City of Moreton Bay Mayor, Peter Flannery said the investigation was fundamental to building an understanding of the extent of damage from a potential future earthquake, while enabling realistic scenario planning for response and recovery.
“Any project like this, where we can get a better understanding of the risks posed by potential disasters, is invaluable,” he said.
“It means we can not only better plan for the infrastructure needs of our community but also work towards how we respond to a future event.”
UoM Professor of Earthquake Science, Dr Mark Quigley said the use of LiDAR allowed the team to laser scan the earth’s surface to identify evidence of where large earthquakes had ruptured the ground thousands of years ago.
“Essentially, what we’re looking for are places where young sedimentary materials are broken by faults or pass across faults unbroken, and we can use those to guide studies to determine the timing and the magnitude of past earthquakes,” he said.
Dr Quigley said the second phase of the study involved analysing sediment samples collected from the scarp which are currently being dated by University of Melbourne researchers.
The results will be compared to the findings uncovered from the team’s earlier LiDAR mapping data.
“This is effectively geological detective work; we’re uncovering the mysteries of these past earthquakes,” Dr Quigley said.
“We dug a trench perpendicular to the trace of the fault in the landscape, digging down several metres.
“We then mapped what’s been broken by those earthquakes in terms of the faults and what passed through that fault zone unbroken. Through dating techniques, we’re then able to get a picture of when this earthquake roughly occurred, how big the magnitude was, and how much displacement occurred at this location.
“From that we can build scenarios around earthquake hazards for all sorts of end users.”
Council Local Disaster Management Group Chair, Councillor Matt Constance said the valuable information gained through the project would be key to ensuring Council is thoroughly prepared to deal with any future scenarios.
“The insights from this study will improve our preparation and preparedness, with data feeding into exercises performed alongside allied agencies and emergency partners,” he said.
“This really detailed and accurate data, means we, as a Council, and our partners, are better prepared to serve our community in their time of need.”
Unitywater and the Queensland Fire Department also contributed funding to the project.
