## 2 Description of Studied Region and Materials  
China is a mountainous country with complex geological structures, where a variety of natural disasters occur. Yunnan Province is located in the Yunnan-Guizhou Plateau of Southeastern China, where 94% of the whole province area is mountains. Among 125 counties and cities located in Yunnan Province, there are only 13 cities with less than 7 degrees of fortification intensity, while there are 56 cities beyond 8 degrees. Most of these cities are located in mountainous areas. Facing the interacted pressures of both urban land restrictions and complex geological structures, layout planning for an emergency shelter system is more prominent. In view of this, this paper used Jianchuan as a case study area to explore the optimal layout of emergency shelters in mountain towns. Located in the northwest of Yunnan Province, China (see Figure 1), Jianchuan county is situated in the southeast of the Qinghai-Tibet Plateau and in the southern part of the Hengduan Mountains. The regional geology of this county belongs to the middle section of the three-river fold belt, which contains several fault zones. Moreover, its geological structure is complex and magmatic activities are frequent as well, thanks to its geographical proximity to the tectonic belt and its correlation with seismic activities (Figure 1). In 2017, a total of 53,600 people lived in a 3.11-km\({}^{2}\) built-up area in the county seat, a small town in terms of population and land scale. Regarding its geological characteristics, although the county is located in an area of relatively flat terrain, the possibility of the occurrence of geological disasters still exists in the west and northwest of the town. In addition to the complicated geological characteristics of Jianchuan, all types of disasters have happened frequently, according to incomplete statistics (since 886 AD, in Jianchuan, 13 earthquakes occurred with a magnitude of over 5 Richter). There were six existing emergency shelters in the Jianchuan county seat as of 2017 (see Figure 1). Although the overall layout of the emergency shelter facilities in the county seat was consistent with its urban layout, challenges still exist. First, the layout of emergency shelters lacked rationality. Due to the insufficiency of urban land, most of the existing urban emergency shelters are indeed the existing parks, squares, schools, public green spaces, and so on. Consequently, it is difficult to ensure the reasonable locations of the emergency shelters. The emergency shelters in the county seat have been mainly located in the north and south of the county seat, and there is no emergency shelter in the center. Second, the scale of emergency facilities was unclear, and the system was mixed. A clear urban emergency shelter system is essential during evacuation conditions and post-disaster relief operations. However, there were no corresponding provisions on the scale of emergency shelters in the master plan of the Jianchuan county seat. Third, the allocation of emergency shelter facilities was not reasonable. Due to the tightness of land use, the existing emergency shelters are mainly configured by using existing parks, plazas, schools, and public green spaces, rather than according to the distribution of the population and the distribution of disasters. From the perspective of the distribution of disasters, the risk of landslides in the northern regions is greater due to the proximity to the mountains. In the ancient city area of the central region, the risk of fire is high because the building materials are mostly wood structures. The disaster risk in the southern region is relatively low. Moreover, the emergency shelters that have been set up are mainly concentrated in the northern and southern parts of the town, but not in the central areas. Meanwhile, the population of the Jianchuan county seat is mainly concentrated in the central and northern regions. Therefore, it is difficult to ensure the rationality of the location of emergency shelters.