Estimation of Damage Scenarios in Mexico City Caused by Nearby Crustal Earthquakes


 Mexico City has sustained severe damage from earthquakes located in the subduction zone and within the subducted Cocos plate. The city lies in the trans-Mexican volcanic belt (TMVB). Earthquakes in the TMVB are relatively infrequent but have reached Mw>6. A recent Mw 6.9 crustal earthquake occurred in 1912, 80 km from Mexico City. Damage scenarios are estimated for two hypothetical crustal earthquakes located 40 and 80 km from the city. The seismic sources represent hazard-critical earthquakes and are based on historical seismicity and on the geological record. The probability distribution of ground acceleration is determined by ground-motion models (GMMs) from similar tectonic regions. Site effects are included to account for the geotechnical zonation of the city, and vulnerability curves are calculated for residential buildings in the cadastral record of Mexico City. The results show that an earthquake near the 1912 earthquake would produce accelerations of 37 and 148  cm/s2 on firm ground and in the lake region, respectively. In this scenario, damage is concentrated in buildings 1-2 stories high located near the transition zone. The earthquake located ∼40 km from Mexico City shows accelerations of 79 and 318  cm/s2 on firm ground and in the lake region, respectively. This scenario concentrated potential damage in buildings 1-2 stories high and broadly distributed in the region underlain by soft clays. Under both scenarios, no damage is expected in buildings higher than ∼11 stories. A deterministic approach using two potential seismic sources instead of a probabilistic seismic hazard model is used because of the lack of background seismicity and the unknown recurrence times of events in the TMVB. The results show very different damage patterns for crustal earthquakes. The two scenarios presented here may be useful for decision makers and insurance companies to estimate physical damage and to implement mitigation programs.