Simulation of household evacuation in the 2014 Ludian earthquake

Earthquake evacuation is important to reduce casualties. To identify the requirements for a successful evacuation, we first investigated the casualties in the Ludian earthquake. Then, a simulation model was developed using a typical building destroyed during the earthquake. This model was integrated with the social force model to describe indoor earthquake evacuation behaviors under different conditions. Instantaneous average speed and social forces were estimated. Finally, the acquired safety escape time (ASET) was determined using finite-element method. We adopted the pedestrian library of AnyLogic software to calculate the required safety escape time (RSET) values under different conditions. We found that RSET was greater than ASET. Thus, people at home failed to escape. RSET varied with escaping velocity. RSET decreased as the velocity increased in a certain range. RSET was influenced by people distribution across rooms. Wall designs affected RSET. A reasonable wall layout could shorten the path distance and consequently reduce RSET. The results of the present work implied that ASET is related to earthquake ground motion (EGM). Seismic energy is concentrated at the start of EGM. Therefore, buildings collapse instantly, and people at home hardly escape from the indoors and must seek temporary security zones in their rooms. In addition, the relative velocity seismic response of a building should be considered.