Evaluation of the risk and the evacuation policy in the case of a tsunami in the city of Iquique, Chile

Abstract

The low seismic activity in the north of Chile has caused a significant accumulation of energy throughout the last two centuries. It is estimated that the energy stored could cause an earthquake of magnitude higher than 8.5 MwMw . This earthquake poses a threat of tsunami to the coastal zone. The city of Iquique is at great risk due to the high demographic density and the long distances between the coastline and the safety zone. An agent-based simulation model has been developed with the objective of quantifying the answer of Iquique’s population under the threat of a tsunami. The model was validated through face validation, sensitivity analysis, and statistical analysis. Two evacuation policies were tested: the current evacuation policy and a policy that combines vertical and horizontal evacuation. The results show that in the diurnal scenario the current evacuation policy does not allow evacuating on time around 40% of Iquique’s population and that the risk may be reduced to 33% by incorporating vertical evacuation. This results are based on the time limit established by local authorities that stipulates a time of 20 min to reach the safety zone. Additionally, we consider an analysis of the simulation model combined with a flooding model. Our results show that the number of people at risk because of a tsunami is much lower than the estimates based on the criteria defined by local authorities. Considering an evacuation policy that combines vertical and horizontal evacuation, it is possible to evacuate over 1500 people more than with the current evacuation policy.