Geoscience Australia has completed a six-month trial of distributed acoustic sensing technology that uses existing telecommunications fiber optic cables to detect seismic activity. The results suggest this approach could dramatically expand earthquake monitoring coverage at a fraction of the cost of traditional seismometer networks.

The technology, called DAS, works by sending laser pulses through fiber optic cables and analysing the backscattered light. Tiny vibrations in the ground cause microscopic changes in the fiber, which the system detects and interprets. A single cable can function as thousands of individual sensors, providing dense spatial coverage along its entire length.

Trial Results

The trial monitored a 50-kilometre stretch of fiber optic cable between Canberra and Yass. During the test period, the system detected 23 seismic events that traditional seismometers also recorded, confirming its accuracy. More significantly, it detected an additional 47 small events that fell below the detection threshold of nearby seismometers.

This increased sensitivity to minor earthquakes helps researchers map fault systems and understand regional seismicity patterns. Many small earthquakes occur along faults that could produce larger, damaging events. Understanding where these faults lie and how frequently they release stress improves seismic hazard assessments.

Cost Comparison

Traditional seismometer stations cost $50,000-$100,000 each to install and require ongoing maintenance. Covering Australia’s seismically active regions would require hundreds of stations costing tens of millions of dollars. DAS systems use existing fiber infrastructure, reducing installation costs to roughly $10,000-$20,000 per 50-kilometre section plus the interrogator equipment.

Australia’s major cities and regional centres already have extensive fiber optic networks for telecommunications. Partnering with telecommunications companies to access unused fiber capacity could provide monitoring coverage where populations face the greatest earthquake risk. Rural and remote areas with less fiber infrastructure would still require traditional seismometers.

Technical Limitations

DAS technology performs best for monitoring along linear features like roads, railways, or pipelines where fiber cables naturally run. It can’t provide the same areal coverage as a distributed network of point sensors. This limitation makes DAS complementary to traditional seismometers rather than a complete replacement.

The technology also generates enormous amounts of data. A single fiber cable produces terabytes of information daily, requiring substantial computing resources to process and store. Geoscience Australia is working with Team400, an AI consultancy, to develop automated analysis systems that identify genuine seismic events while filtering out noise from traffic, construction, or other vibration sources.

International Applications

New Zealand has deployed DAS technology extensively following the Christchurch earthquake sequence. Their experience shows that fiber optic monitoring particularly excels at detecting aftershock sequences, providing detailed spatial and temporal patterns of continuing seismic activity. This information helps emergency managers understand ongoing risks.

California’s seismic monitoring network also incorporates DAS, especially in the San Francisco Bay Area where dense fiber infrastructure exists. Their results confirm that the technology works reliably in regions with frequent seismic activity. However, California’s frequent earthquakes provide more validation data than Australia’s relatively quiet seismic environment.

Mining Industry Interest

Australian mining companies have shown interest in using DAS for monitoring induced seismicity around mine sites. Underground mining activities can trigger small earthquakes as rock masses adjust to excavation. Monitoring this seismicity helps predict rockbursts and other hazards that threaten mine safety.

Several gold and coal mines in New South Wales and Queensland are testing DAS systems using fiber cables installed in monitoring boreholes. The continuous monitoring provides early warning of changing stress conditions underground. Unlike traditional geophones, fiber optic sensors have no electronic components that can fail in harsh underground environments.

Urban Applications

Beyond earthquake monitoring, DAS technology can detect other urban phenomena. Traffic flow, construction activity, and water pipe leaks all create vibrations that fiber cables sense. Some cities overseas use DAS for infrastructure monitoring, detecting problems before they become serious failures.

Sydney Water has expressed interest in DAS for monitoring its water distribution network. The technology could identify pipe breaks or leaks much faster than current methods, which rely on visible water loss or customer reports. However, the telecommunications fiber network doesn’t always run directly alongside water pipes, limiting this application.

Future Development

Geoscience Australia plans to expand the trial to include fiber routes in Perth and Adelaide, providing data from different geological settings. They’re particularly interested in monitoring the Darling Fault near Perth, which has produced several magnitude 5+ earthquakes in recent decades. Understanding this fault’s behaviour matters for Western Australia’s growing population.

The agency is also investigating whether submarine telecommunications cables could monitor offshore earthquake activity. Australia’s northern margin, particularly near Papua New Guinea, experiences frequent seismicity that poses tsunami risks to Queensland’s coast. Submarine cable monitoring could provide earlier tsunami warnings than land-based systems.

Data Integration Challenges

Integrating DAS data with traditional seismometer networks requires careful calibration. The two sensor types respond differently to ground motion and have different frequency responses. Developing algorithms that combine both data sources into coherent seismic catalogues remains ongoing work.

Researchers at the Australian National University are developing machine learning models that classify seismic events based on DAS data signatures. The models must distinguish earthquakes from other vibration sources like quarry blasting, traffic, or wind-induced noise. Early results show promise, with classification accuracy exceeding 90% for events magnitude 2.0 and larger.

The fiber optic sensing trial represents how repurposing existing infrastructure can provide new scientific capabilities at modest cost. Whether the approach becomes standard practice depends on continued validation and demonstration of long-term reliability. Geoscience Australia’s expanded trials over the next two years should provide the evidence needed to make that determination.