Earthquake-induced landslides in Norway

Norway is located in an intraplate setting with low-to-moderate seismicity. The mountainous landscape leads to a high level of landside activity throughout the country. Earthquake-induced landslides (EQILs) are common in seismically active areas, but there are only a few studies of EQILs in intraplate regions. We systematically analyse all earthquakes in Norway with magnitudes =4.5 in the time period 1800-2021 CE. For each event we search for reports of EQILs in the available macroseismic data and in the Norwegian landslide database. We furthermore consider precipitation data from the Norwegian Centre for Climate Services to evaluate the role of precipitation in the triggering of the identified potential EQILs. Through this approach, we identify 22 EQILs that have been triggered by eight earthquakes in the magnitude range 4.5-5.9. The events are widely distributed in northern and southern Norway. The maximum landslide distance limits and landslide-affected areas are much larger than those found in empirical studies of global datasets and are in agreement with data from other intraplate regions. For four of the earthquakes, it seems that landslide triggering was due to a combined effect of precipitation and earthquake ground shaking. Our observations confirm that intraplate earthquakes have the potential to trigger EQILs over large distances, most likely due to the low ground motion attenuation in such regions. Slope susceptibility seems to be another important factor in the triggering. Our conclusions demonstrate the importance of considering EQIL potential in earthquake risk management in intraplate regions.