Toward the Rapid Seismic Assessment of Landslides in Coastal Alaska

As glaciers retreat, landslide-driven tsunamis pose mounting threats across the high latitudes. The recent landslide tsunamis in Alaska and Greenland have spurred efforts to forecast and monitor these events. We use nine large landslides spanning southern Alaska to test an approach for rapid detection and characterization. We use long-period seismograms recorded within three minutes of the start of a landslide to estimate the location and approximate volume. In the presence of good seismic network coverage, location errors are no more than a few kilometers, and detection limits are well below 1 Mm3. The combination of detection time, location, and size provides the ability to rapidly determine whether a landslide occurred close to open water and, if so, its tsunamigenic potential. Our approach is rapid enough to support National Oceanic and Atmospheric Administration (NOAA)’s five-minute tsunami warning goal. The historical analysis we present provides the foundation and parameter tuning for a prototype system that is now providing real-time detections.