Bringing Down Landslides: Measuring landslide mechanics remotely, like seismic networks are used to quantify and locate earthquakes, would provide valuable information to understand these often catastrophic and costly natural hazards.Ekström and Stark(p.1416; see the Perspective byPetley) analyzed global seismic network data using a method that identifies long-period events not recorded by traditional monitoring networks. The global seismic network was able to record landslide events and quantify dynamic properties—including duration, total mass, and direction of debris flow. The analysis located and quantified a series of seven previously undocumented massive landslides associated with the Siachen Glacier in the Himalayas.

Summary. A large number of fundamental-mode Love and Rayleigh wave dispersion curves were determined from seismograms for 3330 earthquakes recorded on 258 glob

We describe and model the evolution of a recent landslide, tsunami, outburst flood, and sediment plume in the southern Coast Mountains, British Columbia, Canada. On November 28, 2020, about 18 million m³ of rock descended 1,000 m from a steep valley wall and traveled across the toe of a glacier before entering a 0.6 km² glacier lake and producing >100‐m high run‐up. Water overtopped the lake outlet and scoured a 10‐km long channel before depositing debris on a 2‐km² fan below the lake outlet. Floodwater, organic debris, and fine sediment entered a fjord where it produced a 60+km long sediment plume and altered turbidity, water temperature, and water chemistry for weeks. The outburst flood destroyed forest and salmon spawning habitat. Physically based models of the landslide, tsunami, and flood provide real‐time simulations of the event and can improve understanding of similar hazard cascades and the risk they pose.

The relationship between bulk‐mass dynamic properties of catastrophic landslides and the generation of short‐period seismic waves is investigated, with a particular focus on the momentum of the landslide mass and the envelope of high‐frequency seismograms. Twelve very large landslides that occurred in different geological settings worldwide between 1999 and 2014 are selected for study, based on the existence of detailed descriptions of their force histories, determined from long‐period seismic waves (frequency lower than 0.1 Hz), as well as the availability of nearby high‐quality short‐period seismic recordings. A high average correlation (0.94) is found between the modulus of the landslide momentum and the envelope of the high‐frequency seismograms, band‐passed filtered between 3 and 10 Hz, recorded on nearby stations. The best correlation is seen during the acceleration phase of each landslide. Comparatively poor average correlation (0.57) is found between the modulus of the landslide force and the seismogram envelopes. A possible scaling between the momentum and the amplitude of short‐period radiation is investigated. The maximum amplitudes of short‐period seismograms for the nine best recorded landslides are corrected for local attenuation and correlated with the maximum momentum of the landslides. The nine data points scatter around a best fitting line that defines a nearly linear relationship between momentum and peak short‐period radiation. It is hypothesized that bulk‐mass momentum linearly modulates landslide processes that generate short‐period seismic waves but that the efficiency of short‐period radiation is highly variable between landslides.