Since 2020, Barry Arm Slide in Prince William Sound Alaska (USA) has been monitored 24/7 by a seismic network and ground shift measurement equipment. This area is among the world's most high-risk groups because with just one sudden landslide, a huge mass of rock and soil could plunge straight into a narrow bay, creating a super typhoon at unusual altitude.
When analyzing the collected data, Gabrielle Davy's team (University of Alaska Fairbanks) identified a completely new layer of seismic signals: Short, sharp, and high- frequency pulses, which appear sparsely in late summer but thicker in the fall - winter, then suddenly disappear in late winter or early spring.
According to research published in Seismological Research Letters, strange earthquakes are likely to arise from the water process in the micro-cracks of the frozen rock and melt seasonally.
The micro-pressure in the ice caused the rock to "break brittle", creating a signal like small jumps underground.
Although not directly related to the movement of the slide, these signals reflect changes within the hydraulic and mechanical systems of the rock - a factor that can affect the time when the slide is unstable.
The Barry Arm Slide is a rock and soil block of about 500 million m3, which has been moving slowly for decades. The sharp retreat of the Barry Glacier ice over the past century has caused the rock foundation to lose its fulcrum and become weaker.
If a rapid landslide occurs, all the material will fall straight into the bay, causing a Tsunami similar to the Lituya Bay event in 1958 - a supertsune of more than 500m that killed the vegetation around the bay.
The risk is even more worrying because this area is a famous tourist destination, with tourist boats, kayakes and near the Whittier community. Therefore, early detection of unusual signals is of survival significance.
To classify seismic signals, Davys team viewed all the data continuously for one year. The method takes time but helps them understand the natural signal background - from the vibration of ice, small earthquakes to environmental disturbances.
After identifying strange signals, the team compared them with weather data, rainfall and ground radar. All are in line with the seasonal freezing - melting mechanism, reinforcing the theory that cracking in the rock is the main source of issuance.
Similar signals have also been reported in Norway during an unstable slide, suggesting that this could be a common phenomenon in the ice zone.
Co-author Ezgi Karasözen said the Alaska Earthquake Center has tested a landslide warning system at Barry arm. When completed, the system will send a warning immediately if a major collapse is detected.
According to her, when it occurs, landslide activity is one of the most important indicators to help reduce risks.
Scientists expect that when the data is accumulated large enough, predicting the time when a slide becomes dangerous will be more feasible. The discovery of new signals not only expands knowledge about the geological environment under the icebergs but also helps the world get closer to the goal of early warning of super-tsunics - an extremely rare type of disaster on Earth but the destructive power is far beyond conventional savings.
