## 4 Results and Discussion  
### Location-Allocation Results of Fixed Emergency Shelters  
In the case study, by running a minimized facility point model with ArcGIS software, we can obtain the minimum number of facilities needed to cover demand points in the study area. The modelcalculation takes the actual length of the county road in the Jianchuan County Seat as the travel cost, and the impedance transformation defaults to linear. The results indicate that the number of fixed emergency shelters required to achieve coverage for all demand points is 18. In terms of fairness, all emergency shelters should cover 100% of the demand points in the study area so that everyone at each demand point can reach the nearest emergency shelter within the specified travel time. But in reality, the spatial distribution of the population is uneven. The main urban area has a relatively dense population distribution, while the suburban area has a relatively scattered population distribution and a low population density. Therefore, the large number of emergency shelters placed in these areas tends to result in low usage rates. In terms of economy, it is very unreasonable to set up emergency shelters in these areas. On the basis of minimizing the facility point model, running the minimum impedance model can simultaneously consider the fairness and economy of the emergency shelter, and finally determine the number of fixed emergency shelters. The model calculation takes the actual road length of the Jianchuan county seat as the travel cost, and the number and coverage of the emergency shelters in the model calculation process are shown in Table 2. Considering the efficiency principles of emergency shelters, the minimized impedance model is run on the basis of minimizing the facility point model, which minimizes the travel cost as well. The number and coverage of the fixed emergency shelter facilities in the Jianchuan county seat are shown in Table 2. To comprehensively assess the factors affecting emergency shelter configuration, both fairness and efficiency principle, ultimately eight facilities were selected (its coverage rate reached 80%). The fixed emergency shelter is the main place for long-term refuge and centralized rescue in cities. In the optimization process of site selection, the following principles are mainly considered: (1) the geographical conditions, demonstrating that the fixed emergency shelters should be located in flat terrains with better geological conditions, as well as avoiding the influence area of the earthquake fault zone; (2) traffic conditions, meaning that the layout of the fixed emergency shelters should be located in an area with convenient transportation, and guarantees at least two roads connecting the main roads with the width of at least 7 m; (3) infrastructure conditions, showing that the fixed emergency shelters should be set in areas with better basic conditions; (4) the distribution of the existing emergency shelters, meaning that the location selection of emergency shelters should consider the distribution of the existing emergency shelters and avoid the over concentration of facilities; and (5) the population distribution, demonstrating that the distribution of fixed emergency shelters should be adjusted according to the distribution of the population. Based on the analysis of the location selection of the fixed emergency shelters, the Jianchuan county seat is located in the relatively gentle section of the dam area and the variation in slope is small. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Number of Facility Points** & **Number of Demand Points Covered** & **Coverage Rate (\%)** \\ \hline Less than 6 & & Less than 75.00 \\
6 & 333 & 75.17 \\
7 & 346 & 78.10 \\
8 & 356 & 80.36 \\
9 & 364 & 82.17 \\
10 & 371 & 83.75 \\
11 & 378 & 85.33 \\
12 & 383 & 86.46 \\
13 & 386 & 87.13 \\
14 & 399 & 90.07 \\
15 & 411 & 92.78 \\
16 & 425 & 95.94 \\
17 & 432 & 97.52 \\
18 & 443 & 100 \\ \hline \hline \end{tabular}
\end{table}