The Valdivia earthquake, the most powerful earthquake ever recorded, occurred on 22 May 1960. With over 50,000 casualties and more than 2 million people affected, the earthquake forced the organising committee to completely modify the World Cup's calendar. Talca, Concepción, Talcahuano and Valdivia were severely damaged and discarded as venues. Antofagasta and Valparaíso declined to host any matches as their venues were not financially self-sustainable. Viña del Mar and Arica managed to rebuild their stadiums while Braden Copper Company, then an American company that controlled the El Teniente copper mine, allowed the use of its stadium in Rancagua. The most used stadium was the Estadio Nacional in Santiago, with 10 matches; the Estadio Sausalito in Viña del Mar hosted 8 matches, and the stadiums in Rancagua and far-away Arica (the only location that was not close to the other cities) both hosted 7 matches.