San Andreas may not be our main worry

After the recent 5.1 earthquake that shook Los Angeles last Friday, USGS warns that the fault system where this quake happened may be a greater reason to worry than the more widely known and feared San Andreas fault. The fault that the Friday tumbler happened on was the Puente Hills fault system, labeled as a ‘blind thrust fault’. It is a fairly shallow fault system and it is suspected of being capable of producing very powerful earthquakes. This coupled with the fact that it runs under some very heavily populated areas with older buildings, essentially from northern Orange County up through downtown LA to Hollywood, gives it the potential to be very destructive and deadly.

According to USGS a potential earthquake on the Puente Hills fault under Los Angeles could result in 3,000-18,000 fatalities, 142,000-735,000 displaced households and more than $250 Billion in total damages. This is actually not something completely new, this study was published in 2005 in “Earthquake Spectra”  the EarthQuake Engineering Research Institute’s online magazine, it was just brought to light by the Friday quake that happened on this fault system.

The Puente Hills fault was discovered in 1999 and in a 2003 study by Southern California Earthquake Center (SCEC) it was found to have ruptured at least 4 times in the past 11,000 years resulting in Earthquakes with magnitudes from 7.2 to 7.5 on the Richter scale. The study also points out that a rupture on this fault is a rare event thought to have the possibility of occurring once every 3,000 years or so…