M5.1 Earthquake hits La Habra

From the USGS – Updated:

http://earthquake.usgs.gov/earthquakes/eventpage/ci15481673#summary

intensity

lahabraci15481673_ciim

Event Time

  1. 2014-03-29 04:09:42 UTC
  2. 2014-03-28 21:09:42 UTC-07:00 at epicenter
  3. 2014-03-28 21:09:42 UTC-07:00 system time

Location

33.919°N 117.944°W depth=7.5km (4.6mi)

Nearby Cities

  1. 1km (1mi) S of La Habra, California
  2. 4km (2mi) W of Brea, California
  3. 5km (3mi) NNW of Fullerton, California
  4. 6km (4mi) E of La Mirada, California
  5. 546km (339mi) W of Phoenix, Arizona

Tectonic Summary

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.

The demonstration earthquake early warning system provided 4 second warning in Pasadena.

Related Links

Tracks remain on Park Blvd

Walking today, I saw that the former San Diego Electric Railway tracks in the median of Park Blvd seem to be staying put. Construction is underway for a “busway” which is tearing out most of the old track and poles. However, at Howard Ave, the tracks are being left in place and reburied beneath the new median. Why this is the case here and not anywhere else is something of a mystery. Hopefully it marks a trend to keep some of the old infrastructure in place instead of destroying it.

Section of rail removed at Howard Ave.
Section of rail removed at Howard Ave.
South of Howard Ave to near Polk Ave, the old rails remain.
South of Howard Ave to near Polk Ave, the old rails remain.

Welcome!

Welcome to the new Southern California Regional Rocks and Roads Page! This site is the combination of the “Los Angeles Rocks and Roads Page” and the “San Diego Rocks and Roads Page”. After having some trouble with the previous host server, I moved to a new host and am now able to better update the site. All of the previous pages are still around though some may have been moved or merged with others.

The new format of the site should also allow for easier access to the immense amount of information this site contains. Parts of the site date back to 1995, when the Santa Clarita Valley Resources Page first went online. Initially, the site was just a single page with some photos. Through the years, the site has been greatly expanded and modified. In 2008, the Santa Clarita Resources Page was transformed into the Los Angeles Rocks and Roads Page, with some of the pages removed and others merged.

In 2006, I added the San Diego Rocks and Road Page, having moved here in 2005. I thought it would be a good addition as there is quite a bit to cover here. The San Diego site had a slightly different focus, with kayaking and local bicycling information as well as highway history.

Now, in 2014, the websites are undergoing a bigger change. Both the scvresources.com and sdrocksnroads.com sites are being merged with the new socalregion.com. This will allow a greater area to be covered with even more photos and information to be shared. I plan to use the new format to help expand the site and make it an even better resource for all of Southern California.