Wednesday, August 8, 2012

Swarm Of Quakes Rattle Los Angeles, CA

A series of moderately sized earthquakes and associated aftershocks hit the Los Angeles (Yorba Linda) area in California today and yesterday, with two quakes registering 4.4 and 4.5 on the Richter scale being the largest tremors. Residents as far south as San Diego County reported feeling the quake, and near the epicenter it was reported to feel quite strong. The quake depths were from 10km-8km for the largest tremors. Many shallower aftershocks, most at or around M2.2 (but some at 2.9) have occurred, and are still occurring as of now.

Los Angeles is no stranger to earthquakes, and as such, has building codes that normally prevent any damage. In California, most buildings must be built to be able to withstand up to a magnitude 8.0 quake as a building standard.

Interestingly enough, the quakes did not occur on the famed San Andreas fault line that extends from Baja California, Mexico, to central California in the US. These quakes occurred some 35 miles SW of the nearest point to the fault at Cajon Junction. These quakes occurred on a smaller fault that runs under Yorba Linda. This fault line is quite small compared to its larger, more violent neighbor, the San Andreas, running only tens of miles in a NW/SE direction. (Given that this is a volcano blog, I should note that these quakes are in NO WAY related to any type of volcanism).

It is likely that more smaller aftershocks will follow for a few days in the area as the fault settles down. It is possible that these quakes may destabilize other faults in the area, however at this time this is only a 'maybe', as scientists still struggle to really figure out how parallel faults affect one another. Earthquake dynamics are highly complex with many factors that go into causing them, and even more factors in the aftermath to consider. 


  1. This is very interesting to me, as I live pretty much ON the San Andreas in Valencia; however The Yorba Linda area has been extremely active lately... I was in the area back in June when one of the first occurred and they've been hit steadily since then. Maybe the baby fault is jealous of its famous big brother? Haha Whatever the case, it's intriguing.

  2. Most of Southern California has experienced heightened seismicity since the Easter 2010 quake that struck Mexico, the 7.4 Magnitude quake that struck caused thousands of smaller quakes up and down the faults. My theory is California is still adjusting crustally to the quake, and we will probably see a few of these pop off. I'd personally LIKE to see some small ones fire off of the San Andreas fault, as it appears that it has probably built up more tension, rather than less, as a result of the Easter Quake. Maybe the Yorba Linda swarm might dislodge something before the San Andreas releases "The Big One" and releases some tension... That would be nice.

    I live in San Diego, and we definitely felt the 4.5 one a little.

  3. I felt both of the Yorba Linda, CA earthquakes. Yesterday's quake was a sharp one, Tuesday night at 11:23pm. Then today, Wednesday 8-8-2012 at some time around 9:30am another one struck! I have lived in the Los Angeles area all my life, and this was just like most of the other quakes, a rolling one, with quite a sharp jolt. I always tell my friends, "my heart never skips a beat!" I am so used to these California earthquakes. And now I am living in Yorba Linda, and I find that I am situated right on top of another faultline!

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