A team from UC San Diego's Scripps Institution of Oceanography analyzed hydroacoustic data from hydrophones maintained by the International Monitoring System under the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). Their findings pinpoint the probable source of the disturbance to the Trou Sans Fond Canyon, a deep underwater valley off the coast of Ivory Coast.
According to Vaibhav Vijay Ingale and his colleagues, the timing and location of the detected acoustic signal correspond with the rupture of four submarine cables in the region. The research, published in *Seismological Research Letters*, marks a pioneering instance of identifying a submarine landslide solely through hydroacoustic monitoring.
"This detection off the Ivory Coast is particularly exciting because it demonstrates the potential of using existing hydroacoustic data to monitor submarine landslides more effectively," Ingale explained. "It suggests that there could be many more events like this happening that we're simply not aware of, either due to a lack of monitoring infrastructure or because we haven't been actively looking for them in the hydroacoustic data."
The breaks occurred on March 14, 2024, roughly 107 kilometers offshore from Abidjan. Given the widespread internet outages that followed, investigators aimed to determine the root cause. The research team turned to hydrophones near Ascension Island, part of the CTBTO network, which had captured a suspicious low-frequency signal two days earlier, on March 12.
"When we examined the hydroacoustic data recorded between March 6 and March 22, 2024, a low-frequency signal on March 12 caught our attention," said Ingale.
The anomalous signal lasted under 90 seconds and was detected only on ocean-based sensors, not land stations. Cross-referencing seismic data revealed no coinciding tectonic activity, strengthening the case for a landslide as the source.
"Since this was the first instance of detecting a submarine landslide with hydrophones that wasn't associated with an earthquake or eruption, there was no precedent for how the signal should appear," Ingale noted. "We had to carefully scan the available data for anomalous patterns that didn't resemble known tectonic or volcanic signals. The difficulty was compounded by the fact that hydrophone data can be noisy due to ocean sounds like marine life, vessel traffic and other anthropogenic interactions."
After confirming the origin of the signal, the team used its characteristics to triangulate the landslide's location. The calculated epicenter aligned closely with the position of the damaged cables and the steep seafloor terrain of the Trou Sans Fond Canyon.
Ingale emphasized the broader significance of the discovery, suggesting hydrophones could support early warning systems for undersea infrastructure operators.
"Furthermore, insights from hydroacoustic monitoring can lead to better engineering standards, such as deeper burial of cables in sediment-prone areas or rerouting around historically unstable slopes," he added. "In cases where a cable break occurs, analyzing hydroacoustic data can help determine whether a landslide was the cause, aiding forensic analysis, insurance claims and understanding broader risks to undersea infrastructure."
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