The 1971 San Fernando earthquake (also known as the Sylmar earthquake) occurred in the early morning of February 9th, 1971. 

64 people were killed and more than 2,500 injured. 

Both the Veteran's Administration Hospital and Olive View Medical Center in Sylmar were severely damaged, accounting for many of the deaths. 

The quake also tore apart freeway overpasses and the Van Norman Dam, which held more than 3.5 billion gallons of water just northwest of San Fernando. Part of the dam crumbled in the quake, and more damage was reported with each aftershock.

Residents along the 405 Freeway were evacuated for days until the dam was shored up and determined to be safe.

Sources : WIKIPEDIA