## 2 Methods
### Pre-Earthquake Phase
#### 2.1.2 Indoor Population Rate  
The indoor population rate is used to describe the presence of people in a building during a certain period, which involves many factors, such as the specific time of day (day, night, and holidays), weather conditions, occupant density, population size, and the living and production conditions of the residents. In the field of earthquakes, the indoor population rate is mainly related to geographical location, working days and non-working days, age of residents, buildings with different functions, earthquake occurrence time, population structure, and occupation. Of course, some factors are indefinite, such as climatic conditions and interim policies. The occupancy rate is the ratio of the number of people in the building to the accommodated population, and it takes a value in the range of 0-1. In previous studies, the indoor population rate is mostly determined for a specific area based on surveys of local occupancy patterns, requiring significant human and financial resources, which are not universally applicable. Moreover, the indoor population rate with buildings of detailed function has been less studied. To obtain the results of indoor population rate with universal applicability, we studied the results of indoor population rate with universal applicability based on Sichuan population's activity literature [27; 28]. The specific relationships are shown in Figures 3 and 4. The indoor population rate is considered to be related to a variety of factors, both definite and indefinite, such as the moment of earthquake, working days or rest days, population size, population structure, occupation, and building function. Individual movements of people are more random, but group population movements have a certain regularity. Each day can be divided into two categories: working day or rest day, and the  
Figure 4: Indoor population rate in rest day. Figure 3: Indoor population rate in workday. 24 h day can be divided into 7 periods. Stage A stands for sleep period (22:00 the previous day to 06:30 the next day). Stage B stands for morning commute (06:30-08:00). Stage C stands for working period (08:00-12:00). Stage D stands for rest period (12:00-13:30). Stage E stands for working period (13:30-17:30). Stage F stands for evening commute (17:30-19:00). Stage G stands for rest period (19:00-22:00). By analyzing the behavioral characteristics of the population at various times of the work and rest day, the economic census data are combined to quantify the indoor population rate. The social activity patterns of the various sectors and the indoor population rate of the functional buildings are summarized in this study. The indoor population rate of each functional building on working days is shown in Figure 3 and the indoor population rate of each functional building on rest days is shown in Figure 4.  
For buildings with weekday accommodation service, the indoor population rate is 0.95 in stage A, when the population is basically asleep. In stages B-F, during working hours, only the elderly and young children (0-2 years old) are present in buildings with this function, so the indoor population rate is 0.2. In stage G, when the population is resting at home after work, the indoor population rate takes 0.8. For buildings with a rest day accommodation service, the indoor population rate is still 0.95 in stage A. In stage B and G, there are trips, so the indoor population rate is 0.6. In stages C-F, there are generally home and travel behaviors, so the indoor population rate is taken as 0.4. The hospital service is divided into inpatient and outpatient, with medical and nursing staff, outpatients, inpatients, and escorts during daytime, and inpatients, escorts, and medical and nursing staff on duty at night. Therefore, the indoor population rate of stage A, B, F, and G is basically the same as 0.5. The indoor population rate of stage C and E is 0.9 for working hours. During lunch break, medical and nursing staff and accompanying staff are out, so the indoor population rate of D is 0.7.