An alternative to landslide volume-area scaling relationships: an ensemble approach adopting a difference model to estimate the total volume of landsliding triggered by the 2016 Kaikōura earthquake, New Zealand

Abstract Evaluating the influence of earthquakes on erosion, landscape evolution, and sediment-related hazards requires quantifying the number, location, and volume of co-seismic landslides following large earthquakes. Direct measurements of individual landslide volumes are difficult to accomplish and, as a result, rarely attempted. As an alternative, power-law scaling relationships between landslide volume and area—derived from global landslide inventories—are often used to estimate landslide volumes. The accuracy of the volume estimates derived from using these global scaling relationships remain untested and could be a source of significant uncertainty. Here, an ensemble method, adopting a pre- to post-event 2 by 2 m difference model covering an area of 6875 km 2 , has been developed to accurately estimate the volume of the > 30,000 mapped landslides triggered by the 2016 Mw 7.8 Kaikōura earthquake New Zealand. Our ensemble method estimates the total landslide volume for the Kaikōura earthquake to be 241 (+ 100/ − 69) M m 3 . This newly quantified total volume estimate of co-seismic landsliding was then compared to the total volumes estimated using globally and locally derived scaling relationships, which were found to underestimate the total landslide volume by up to 52%. As an alternative, we recommend that landslide volumes be estimated by sampling directly from high-quality empirical datasets of individual landslide volumes with similar triggering and physiographic settings.