Scientists from The Australian National University (ANU) have utilized traffic-generated vibrations along the Federal Highway to gain insights into the seismic history of Lake George, located to the north-east of Canberra. Their findings offer groundbreaking information about the structural features of the Lake George fault zone, which is positioned along the western edge of the lake.
The researchers assert that this fault zone contains significant evidence regarding historical earthquakes in the region. Their analysis revealed that Lake George exhibits seismic traits comparable to several prominent fault systems globally, including California”s infamous San Andreas Fault.
“Earthquake faults can pose serious risks, especially in populated areas. To assess the potential dangers of a fault, scientists require detailed underground maps,” stated Dr Chengxin Jiang, the lead author of the study. “However, creating such maps can be challenging, particularly in urban environments, as it demands effective, non-invasive, and environmentally friendly techniques.”
Employing a network of 100 seismometers, each roughly the size of a beer can, the team placed these devices in the dry lakebed and adjacent to the highway. They analyzed the vibrations caused by traffic and utilized this data to construct three-dimensional images, enabling them to examine up to 800 meters below the Earth”s surface—akin to performing a CT scan for detailed medical imaging.
“By synchronizing and analyzing the data collected by the seismometers, we have successfully generated the first detailed visualization of the lake”s fault zone, which enhances our understanding of its structure and seismic properties,” Dr Jiang explained. “The Lake George fault zone extends approximately 80 kilometers and is one of three significant fault systems near Canberra, still considered active today.”
The Geoscience Australia earthquake catalog indicates that around 50 earthquakes with magnitudes between 1 and 3.5 have occurred within a 5-kilometer radius of this fault over the last 60 years. Furthermore, it is known that Lake George may have experienced numerous earthquakes of magnitude 7 during the past 4 to 5 million years, a history that likely influenced the lake”s current topography, including the hills visible to the west.
Professor Meghan Miller, a co-author of the study, remarked that conventional methods for examining fault zones are often difficult and costly, frequently relying on artificial explosions. She emphasized that using traffic noise to investigate these zones presents an innovative, powerful, and non-invasive alternative for conducting seismic hazard assessments in urban areas or regions that are challenging to reach.
“This approach has enabled us to analyze the structure and features of a fault zone in unprecedented detail,” she noted. “The results shed light on the magnitude of earthquakes that have impacted the Lake George fault in the geological past, allowing us to compare it with other seismically active regions today.”
According to Professor Miller, the small and portable nature of the seismometers allows for rapid installation in the ground and facilitates deployment in various locations, making it a convenient solution for scientists aiming to study fault zones worldwide. “This technique could even assist in exploring underground resources without causing surface disruption,” she added.
The research team gathered data from the traffic vibrations along the Federal Highway for approximately four weeks, from December 2020 to January 2021. The results of their investigation are published in the journal Seismological Research Letters.
Images related to the research can be accessed through the ANU website.
This project received support from AuScope and the Australian Government via the National Collaborative Research Infrastructure Strategy (NCRIS), with additional funding from an Australian Research Council Discovery Early Career Researcher Award.
