The 1971 Sylmar Earthquake. By Kenneth Lafler.

 

 

On February 9th at about 6 in the morning

the San Fernando Valley was rocked by one of the worst earthquakes in it's history. In fact this was one the worst earthquakes to hit an Urban area. The only thing keeping this from being far worse was the time of day it struck.

Had this quake been just three hours later the fatalities would have been far higher due to the traffic on the freeways with commuters on their way to work.

 

 

 

 

 

Also the fact that the Van Norman Dam did not  fail kept the death toll down. The Dam's water level had been lowered for repairs, so the dam did not completely fail but had a partial collapse. 

 

 

 

 

If this dam had  fully collapsed the number of fatalities could have been in the thousands.

Being over one hundred feet in height, the dam would have sent a huge wave into the homes directly below the dam, flooding the Granada Hills area and most of the housing on that side of the freeway. 

 

The strange irony of this was that Harvey Van Norman had been deputy engineer on the ill fated St. Francis dam which failed catastrophically on March 28th at 12 o'clock at night in 1928 killing hundreds of people while they slept.

 

 

 

The Quake was centered on the then unknown Placerita Fault, in Newhall. Geologists had no idea the fault existed, similar to the Northridge Quake. 

 

 

         
The Quake registered at 6.6  on the Richter Scale. There are two scales for measuring earthquakes, Richter and the Mercali Scale. The Mercali Scale goes higher than the Richter Scale so the Sylmar earthquake would have a much higher reading on Mercali.









  Liquefaction played an important part in the amount of damage from this quake. Some area's such as Panorama City which has a much higher ground water level were hit particularly hard. In this situation the ground actually turns to quick sand. Many homes simply slid off their foundation's.






   One of the hardest hit buildings was the Olive View Medical Center.  One section of the hospital grounds completely collapsed trapping hospital patients. The death toll at the hospital was about 66. Olive View has since been rebuilt.

A patrol officer on duty actually fell off of one of the collapsed freeway bridges to his death Near the Newhall Pass area. This area sustained extremely heavy damage to the freeway bridges and overpasses, due to Liquefaction , being next to the reservoir and dam area.

 

 

 

.

For geologists these quakes are an unprecedented view into how major earthquakes function and  the effect on urban centers. The Sylmar Quake and the Northridge quake will probably be studied for as long as there are earthquakes. 

by

Kenneth Lafler