Ground Motions, Infrasound Signals, and Seismic Velocity Perturbations: Environmental Impacts of the Rock Avalanche Induced by the 2025 Mw 6.5 Jan Mayen Strike-slip Earthquake
Résumé fourni par la source
The Jan Mayen Island (JMI) is an activate volcano located in Arctic Ocean, at the Jan Mayen transform fault (JMTF). On 10 March 2025, a strong strike-slip Mw 6.5 earthquake occurred in the JMTF, with the fault rupturing for ~40 km long and crossing the north zone of the JMI, indicating the potential for local hazard effects. Local GNSS sensors indicated that JMI moved ~2.4 cm in WNW-ESE direction during the rupture process, corroborating with the ESE rupture direction identified by apparent duration of regional P-waves (1700-2200 km away), and the local epicenter distribution of the >1500 relocated aftershocks. The epicenter of the mainshock was located ~8 km away from Kjerulf Glacier, a long flowing glacier on the outer crater edge of the Beerenberg stratovolcano. An infrasound array located in northern Norway identified a signal arriving ~3 min after the mainshock, with the source of the signal coming with back-azimuth in direction of the Kjerulf Glacier. Additionally, the ambient seismic noise cross-correlation of three local stations, located ~3-16 km distance from the glacier, revealed subsurface velocity perturbations during ~30 min and starting ~3 min after the mainshock. Using Sentinel-2 and high-resolution MAXAR satellite images, we confirmed that the infrasound signal and seismic noise perturbations were generated by a large volume (2.8 − 6.3x105m3) of basaltic rock that detached and collapsed in the slope located in south wall of the Kjerulf Glacier, minutes after the mainshock occurred. The collapse triggered a rock avalanche that scattered debris along the glacier surface and covered most of the ice toward the border of the sea. It may take several years before the glacier surface covered with rock material returns to its previous state. Therefore, in addition to highlighting the synergy of geophysical, remote sensing, and satellite data in characterizing complex submarine fault slipping, this multidisciplinary study shows that earthquakes along oceanic transform faults can pose serious natural hazards through secondary effects, such as large rock avalanches in the land area near the epicenter.
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