Hazard Assessment of Co-seismic Landslides Based on Information Value Method: A Case in 2018 MW6. 6 Hokkaido Earthquake,Japan

An MW6.6 earthquake occurred in eastern Hokkaido,Japan on September 6th,2018.Based on the pre-earthquake image from Google Earth and the post-earthquake image from high resolution(3 m) planet satellite,we manually interpret 9 293 coseismic landslides and select 7 influencing factors of seismic landslide,such as elevation,slope,slope direction,road distance,flow distance,peak ground acceleration(PGA) and lithology.Then,9 293 landslide points are randomly divided into training samples and validation samples with a proportion of 7:3.In detail,the training sample has 6 505 landslide points and the validation sample has 2 788 landslide points.The hazard risk assessment of seismic landslide is conducted by using the information value method and the study area is further divided into five risk grades,including very low risk area,low risk area,moderate risk area high risk area and very high risk area.The results show that there are 7 576 landslides in high risk area and very high risk area,accounting for81.52% of the total landslide number,and the landslide area is 22.93 km~2,accounting for 74.35 % of the total area.The hazard zoning is in high accordance with the actual situation.The evaluation results are tested by using the curve of cumulative percentage of hazardous area and cumulative percentage of landslides number.The results show that the success rate of the information value method is 78.50% and the prediction rate is 78.43 %.The evaluation results are satisfactory,indicating that the hazard risk assessment results based on information value method may provide scientific reference for landslide hazard risk assessment as well as the disaster prevention and mitigation in the study area.