Worst-case tsunami scenario in Cartagena Bay, central Chile: Challenges for coastal risk management

Abstract

Tsunami risk is analyzed regarding a probable extreme event in Cartagena Bay (33°S), one of the most anthropized areas of Chile and part of its main metropolitan area. An event with characteristics similar to those of the 1730 earthquake (Mw 9.1) was modelled considering the worst-case scenario for the coast of central Chile. Vulnerability is analyzed by applying the Social Vulnerability Index (SoVI) with representative census (2017) variables. A principal component analysis (PCA) was applied to the variables, generating 8 main groups. The results established flooding heights up to 9 m with maximum flow velocities of 10 m/s. The first inundation started 5 min after the earthquake but consecutive hazardous waves were active for at least 6 h after the shaking. Social vulnerability was established as high for the components that made up the following variables: socioeconomic status, housing material, access to basic services and gender, which are directly related to the occupancy, promoted by planning instruments, of dune fields and the periphery of wetlands. The risk area encompasses 99% of the affected area, while 67.5% of the area is at high risk. Mitigation and prevention measures that can be addressed in territorial planning and coastal management are proposed, prioritizing the restoration of the dune system as a natural protection measure against extreme events, the relocation of the population in irregular occupancy conditions, evaluation of tsunami evacuation potential, planning urban design in conjunction with evacuation routes and consideration of vertical evacuation implementation.