# 8413
Overnight, and as 2014’s National Tsunami Preparedness Week winds down, the city of Los Angeles was rocked by a moderately strong earthquake (Mag 5.1), causing some minor damage and rattling nerves across a wide swath of Southern California. Three hours after the quake, the Los Angeles Times was reporting 5.1 earthquake causes damage; some flee from homes.
While a far cry from `the big one’, California residents are advised by USGS seismologist Lucy Jones that there is about a 5% chance that this quake could be a foreshock, and that another – larger quake – could occur in the hours or days ahead (Larger L.A. earthquake possible after 5.1 temblor, USGS says).
First the Tectonic Summary from the USGS, then I’ll be back with a bit more about earthquake preparedness.
A M5.1 earthquake occurred at 9:09PM on March 28, 2014, located 1 mile easy of La Habra, CA, or 4 miles north of Fullerton, CA. The event was felt widely throughout Orange, Los Angeles, Ventura, Riverside, and San Bernardino counties. It was preceded by two foreshocks, the larger of M3.6 at 8:03pm. The demonstration earthquake early warning system provided 4 second warning in Pasadena.
There have been 23 aftershocks as of 10:00PM on March 28, the largest of which was a M3.6 at 9:30PM, and was felt locally near the epicenter. The aftershock sequence may continue for several days to weeks, but will likely decay in frequency and magnitude as time goes by.
The maximum observed instrumental intensity was VII, recorded in the LA Habra and Brea areas, although the ShakeMap shows a wide area of maximum intensity of VI. The maximum reported intensity for the Did You Feel It? map was reported at VI in the epicentral area.
This sequence could be associated with the Puente Hills thrust (PHT). The PHT is a blind thrust fault that extends from this region to the north and west towards the City of Los Angeles. It caused the M5.9 1987 Oct. 1 Whittier Narrows earthquake.
Previously, the M5.4 2008 Chino Hills earthquake occurred in this region. It caused somewhat stronger shaking in Orange County and across the Los Angeles Basin.
The moment tensor shows oblique faulting, with a north dipping plane that approximately aligns with the Puente Hills thrust.
Last December, in Dr. Lucy Jones: `Imagine America Without Los Angeles’, we looked at a presentation given by Dr. Jones at the annual meeting of the American Geophysical Union (held this year in San Francisco), that emphasized that should the `big one’ hit Southern California, we could literally `lose’ Los Angeles.
She warned that the damage could be far greater, and last much longer, than most people believe. While 99 out of 100 modern buildings might remain standing, the (often buried) infrastructure needed to provide water, electricity, internet connectivity, and natural gas – the lifeblood - to the region could be devastated (see CBS News report).
If this sounds like hyperbole, in 2010 (see Revised Risk Of `The Big One’ Along San Andreas Fault) we looked at a study that suggested that Southern California may be more overdue for another major quake than previously thought, and in the following year (see Estimating The Economic Impact Of A San Andreas Quake) we looked at a report from the U.S. Bureau of Labor Statistics that endeavored to gauge the crippling impact that a highly feasible (and long overdue) 7.8 magnitude Southern California earthquake would have on jobs and local businesses.
A quake of this magnitude, they estimate, could affect 430,000 businesses and 4.5 million workers and deliver a devastating – and prolonged – blow to the local (and national) economy.
For a comprehensive guide on how you can prepare for `the big one’ (even if you live someplace other than Los Angeles), I would recommend you download, read, and implement the advice provided by the The L. A. County Emergency Survival Guide.
As you’ll notice, Los Angeles recommends having more than just a 72 hour emergency kit.
It isn’t enough to have a kit, and a plan during an earthquake. You need to know what to do to protect life and limb while the shaking is going on. And for that, we have the ever-growing Great Shakeout Drill (see NPM13: A Whole Lotta Shakeouts Going On).
While there is admittedly a 95% chance that there won’t be a large aftershock to this quake, it only takes being caught unprepared for a single major disaster to ruin your entire day.
For more information on emergency preparedness, I would invite you to visit:
FEMA http://www.fema.gov/index.shtm
READY.GOV http://www.ready.gov/
AMERICAN RED CROSS http://www.redcross.org/
And some of my preparedness blogs, including:
