Scientists Crack Mystery Behind Planet-Shaking Nine-Day Tremors

TDT | Manama

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A year after the Earth mysteriously trembled every 90 seconds for nine days straight—twice—scientists have finally traced the cause of the bizarre global seismic activity. The long-standing mystery has now been put to rest, thanks to a breakthrough study using cutting-edge satellite technology.

In September 2023, seismometers around the world picked up rhythmic tremors occurring at regular 90-second intervals. The unexplained shaking lasted for nine days and reoccurred just a month later. These anomalies defied all known tectonic behavior and left scientists around the globe searching for answers.

Now, in a study published in Nature Communications, researchers led by Thomas Monahan, a Schmidt AI in Science Fellow at the University of Oxford, have confirmed that the unusual seismic signals were caused by two colossal landslides in East Greenland’s remote Dickson Fjord. These massive collapses triggered equally massive "mega-tsunamis," which in turn produced a phenomenon known as seiches—enormous standing waves that repeatedly sloshed within the fjord, creating rhythmic pulses that shook the Earth’s crust.

“Previous studies in 2024 proposed the landslide-tsunami theory based on seismic patterns, but we lacked direct evidence to conclusively prove the link,” said Monahan. “Our research now confirms it.”

The key breakthrough came from data collected by NASA’s Surface Water and Ocean Topography (SWOT) satellite, launched in December 2022. Using a unique radar altimetry technique, SWOT is capable of mapping water levels across 90% of Earth’s surface in stunning detail. While traditional satellites missed the phenomenon due to infrequent measurements and complex fjord topography, SWOT’s high-resolution twin-antenna system succeeded where others failed.

The satellite captured the dynamic surface changes in the fjord as the seiches surged back and forth, providing the first-ever direct observations of the event and allowing researchers to match them precisely with the seismic data.

“This is a prime example of how new technology can transform our understanding of natural phenomena,” Monahan noted.

The findings not only close a major scientific mystery but also open new pathways for monitoring remote and rugged environments using advanced satellite systems. As Earth’s climate continues to shift, such insights could prove vital in understanding and anticipating the impacts of sudden geological events.