Estimation of Damage Scenarios in the Mexico City Basin Caused by Local Crustal Earthquakes

ABSTRACT The recent seismic swarms in the Mexico City basin underscore the need to evaluate their potential implications for seismic hazard and risk in the capital city. Despite their small magnitude (Mc<3.3), these earthquakes caused unusually large ground accelerations, surpassing previous destructive earthquakes. This work aims to forecast seismic damage scenarios resulting from earthquakes in the Mexico City basin. It is assumed that earthquakes as large as Mw 5.5 may occur. Three scenarios were investigated where previous events took place. A deterministic approach estimates ground-motion intensity measures like peak ground acceleration and/or spectral pseudoacceleration, utilizing ground-motion models from comparable tectonic regions. Local site effects were based on the geotechnical zonation of the city. To estimate the damage, vulnerability curves were calculated for residential buildings in the cadastral record of Mexico City. In scenario 1, La Magdalena, ∼13% of 1–2-story buildings would be affected. In scenario 2, San Juan de Aragón, up to 15% of similar structures may be impacted. Scenario 3, Milpa Alta, shows about 5% damage for 1–2-story buildings, primarily concentrated to the southeast. In the three scenarios, 1- and 2-story buildings suffer damage, independent of the geotechnical region. For 3–5-story buildings, damage is concentrated in the lake zone of the basin, where soft sediments underlie the city. For buildings 6–10 stories high, damage lies preferentially in the transition zone between the soft sediments and the highlands. No appreciable damage is observed for buildings taller than 11 stories in any scenario. Local crustal earthquakes, as considered here, represent a significant risk to Mexico City. Outlining damage scenarios may help decision-makers and insurance entities implement mitigation measures to reduce potential impacts on residential structures.