Following the 7.1 magnitude quake on 18 September Tuesday, Emergency workers and the Mexican army responded with rescue work. Authorities have said that buildings collapsed at 44 places in the capital alone. Earlier in the day workplaces across the city held readiness drills on the anniversary of the 1985 quake, a magnitude 8.0 disaster, which killed thousands of people and devastated large parts of Mexico City. In that tragedy, too, ordinary citizens played a crucial role in rescue efforts that overwhelmed officials. Much of Mexico City is built on former lakebed, and the soil can amplify the effects of earthquakes centered hundreds of miles away. The US Geological Survey predicts "significant casualty and damages are likely and the disaster is potentially widespread."