## 3 Data and Method
### Data Source
#### 3.1.2 Influencing Factors of Landslide Susceptibility  
In landslide susceptibility assessment, there is no widely accepted standard for selecting landslide controlling factors [35]. Based on our experiences and literature [17], combining the topographical, geological and seismic aspects, here we selected elevation, slope angle, aspect, curvature, distances to fault, distances to epicenter, PGA, distance to rivers, distances to roads, and lithology to mapping landslide susceptibility in the study area. In areas of similar elevation, seismic landslides are usually equally distributed. Therefore, the elevation was selected as an influencing factor of landslide susceptibility. From a 30 m resolution DEM of the study area, the elevation was divided into seven classes: \(<\)100 m, 100-200 m, 200-300 m, 300-400 m, 400-500 m, 500-600 m, and \(>\)600 m (Figure 8a). Another factor affecting earthquake-induced landslides is the slope features, including its angle, aspect (or facing direction), and curvature. These data were derived from DEM. Based on previous studies [36] and local terrain, the slope angle was divided into five categories: \(<\)10\({}^{\circ}\), 10\({}^{\circ}\)\(\sim\)20\({}^{\circ}\), 20\({}^{\circ}\)\(\sim\)30\({}^{\circ}\), 30\({}^{\circ}\)\(\sim\)40\({}^{\circ}\), and \(>\)40\({}^{\circ}\) (Figure 8b), the aspect was divided into nine categories: Flat, East, South east, North, Northeast, West, Northwest, South, and Southeast (Figure 8c), and the curvature was divided into six categories of \(<\)-2, 2\(\sim\)-1, -1-0, 0-1, 1-2, and \(>\)2 (Figure 8d). Figure 7: The study area and Tomakomai earthquake -triggered landslides (active faults are modified from literature Active fault research group [28] and Nakata [29]. Figure 8: _Cont._  
Because of under-cutting action of rivers or roads may affect the stability of natural slopes, distance to rivers and roads were also selected as influence factors. Distances to rivers and roads were classified by 100m buffer interval. Then, the maps were converted into raster format, respectively (Figure 8h,i). Lithology is a major influence factor on landslide occurrences. The lithology data was from a 1:200,000 geological map of the study area [37], which was divided into 10 categories according to the stratigraphic age groups, including Late Pleistocene lower terrace (Q3 tl), Middle Pleistocene higher terrace (Q2 th), Middle Pleistocene marine and non-marine sediments (Q2 sr), Late Eocene to Early Oligocene marine and non-marine sediments (PG3 sr), Middle Eocene marine and non-marine sediments (PG2 sr), Late Miocene to Pliocene marine and non-marine sediments (N3 sn), Middle to Late Miocene marine and non-marine sediments (N2 sn), Early Miocene to Middle Miocene marine and non-marine sediments (N1 sr), Late Cretaceous marine sedimentary rocks (K2 sm), and Late Pleistocene to Holocene marine and non-marine sediments (Hsr). Strong ground motion is an immediate trigger of seismic landslides. Because the seismic intensity interval is larger compared to PGA, or the same intensity, the upper and lower limits of PGA can be several times different due to the different magnitudes. Therefore, we selected PGA as an index to represent ground shaking. The PGA data used in this work was from the USGS ([[https://earthquake.usgs.gov](https://earthquake.usgs.gov)]([https://earthquake.usgs.gov](https://earthquake.usgs.gov))) The range of PGA for the study area is from 0.16 to 0.82g with a 0.1g interval (Figure 8g). The area ranging from 0.5g to 0.7g accounted for 63.8% of the total area. Most  
Figure 8: Map showing controlling factors and their classes in the study area. (**a**) Elevation; (**b**) slope angle; (**c**) aspect; (**d**) curvature; (**e**) distance to fault; (**f**) distance to epicenter; (**g**) PGA; (**h**) distance to river; (**i**) distance to road; and (**j**) lithology. landslides are concentrated in this area with PGA from 0.5g to 0.7g.