Phys.org September 14, 2024
A large rockslide occurred in Greenland on 16 September 2023 that generated a local tsunami. The event was energetic enough to generate a global signal that resonated for 9 days. An international team of researchers (Denmark, UK, Germany, Belgium, France, USA – USGS, UC Berkeley, UC San Diego, UC Riverside, Boston College, University of Washington, Norway, The Netherlands, Italy, Sweden, Spain, Costa Rica, New Zealand, Indonesia, Greenland) detected the start of a 9-day-long, global 10.88-millihertz (92-second) monochromatic very-long-period (VLP) seismic signal, originating from East Greenland. They demonstrated how this event started with a glacial thinning–induced rock-ice avalanche of 25 × 106 cubic meters plunging into Dickson Fjord, triggering a 200-meter-high tsunami. Simulations showed that the tsunami stabilized into a 7-meter-high long-duration seiche with a frequency and slow amplitude decay that were nearly identical to the seismic signal. An oscillating, fjord-transverse single force reproduced the seismic amplitudes and their radiation pattern relative to the fjord, demonstrating how a seiche directly caused the 9-day-long seismic signal. According to the researchers their findings highlight how climate change is causing cascading, hazardous feedback between the cryosphere, hydrosphere, and lithosphere… read more. TECHNICAL ARTICLEÂ
Landslide-affected slopes around Barry Arm fjord, Alaska… Credit: Gabe Wolken /USGS