Tsunamis generated by mass movements such as landslides, underwater slumps, and rock avalanches can lead to serious inundation of nearby populated areas. The lack of timely estimations of the moving mass volume, however, makes providing operational early warnings for landslides particularly challenging. In June 2017, a large landslide in Greenland generated tsunami waves of about 1 m high that impacted the small town of Nuugaatsiaq. We show how the seismic analysis of real‐time seismic records from the Greenland Ice Sheet Monitoring Network (GLISN) can provide estimates of essential physical properties of the landslide such as collapse mass and sliding velocity shortly after origin time. The estimation of the landslide source parameters can be utilized for tsunami‐wave simulations. We demonstrate how the real‐time integration of seismic waveform inversion with forward tsunami‐wave simulation could have enabled a timely operational warning (about 10 min) before the arrival of the impending tsunami waves at the village of Nuugaatsiaq.

Landslides have caused extensive infrastructure damage and caused human fatalities for centuries. Intense precipitation and large earthquakes are considered to be two major landslide triggers, particularly in the case of catastrophic landslides. The most widely accepted mechanistic explanation for landslides is the effective-stress dependent shear strength reduction due to increases in pore water pressure. The Chashan landslide site, selected for the present study, has been intensively studied from geological, geophysical, geodetic, geotechnical, hydrological, and seismological perspectives. Our seismic monitoring of daily relative velocity changes (dv/v) indicated that landslide material decreases coincided with the first half of the rainy period and increased during the latter half of the rainy period. The geodetic surveys before and after the rainy period identified vertical subsidence without horizontal movement. The results from the multidisciplinary investigation enabled us to draw a conceptual model of the landslide recovery process induced by water loading. Where all sliding materials were stable (safety factor > 1.0), unconsolidated landslide colluvium and impermeable sliding surfaces trapped the seepage water to form a water tank, provided that compact forces were acting on the materials below the sliding boundary. The vertical force of compaction facilitates an increase in the cohesion and strength of landslide materials, thereby increasing the landslide materials’ stability. We demonstrated that the recovery process periodically occurs only under the combined conditions of prolonged and intense precipitation and the related stability conditions.