Loma Prieta earthquake aftermath, Marina District, San Francisco, California, USA. Construction worker surveying property damage caused by the Loma Prieta earthquake. The earthquake, which occurred on October 17 1989, lasted 15 seconds and had a surface magnitude of 7.1. It was the worst earthquake in the San Francisco Bay area since 1906. A tsunami wave measuring around 1.2 metres in height travelled from Santa Cruz to Monterey. The earthquake killed 63 people throughout northern California and many properties were destroyed, which left more than 12,000 people homeless.