EVALUATION OF EARTHQUAKE-INDUCED SLOPE FAILURE DISTRIBUTION USING THE AHP METHOD AND GIS

Abstract

Landslides or slope failures are often caused by earthquakes. The 2018 Hokkaido Eastern Iburi Earthquake and the 2016 Kumamoto Earthquakes in Japan caused many slope failures that were distributed both widely and densely. This study proposes an earthquake-induced slope failure hazard mapping method that uses the analytic hierarchy process (AHP) and a geographic information system (GIS) for specific districts, the Atsuma district in Hokkaido and Minamiaso district in Kumamoto. The earthquakeinduced slope failure hazard assessment system used here is based on the landslide distribution (NIED catalog, Japan), which includes tens of thousands of locations in the Atsuma and Minamiaso districts. We considered the relationships between landslide distribution and landslide hazard factors (elevation, slope angle, slope type, catchment degree, geology, and vegetation). These relations were introduced to pairwise comparisons of factors in the AHP method. The AHP method was applied to evaluate the slope failure hazard rank. An earthquake-induced slope failure hazard map was created based on slope failure hazard ranks of I–V. As a result, slope angle, slope type, and catchment degree were found to exert maximum effects on slope failure distribution due to earthquakes in both the Atsuma district in Hokkaido and the Minamiaso district in Kumamoto. The two earthquake-induced slope failure distributions are almost consistent with the slope failure hazard rank. These results provide a practical method for evaluating earthquake-induced slope failure hazards.