1987 Whittier Narrows earthquake

The Whittier Narrows earthquake struck the southern San Gabriel Valley and surrounding communities of southern California at 7:42 a.m. (Pacific Daylight Time) on October 1, 1987. The magnitude 5.9 earthquake was originally assigned a magnitude of 6.0 but was revised a few days later when additional data became available. Its epicenter was actually in the town of Rosemead, California, at a depth of 11 km.

The earthquake was caused by slip on a blind thrust fault near the northern end of the Whittier Fault, part of the Elsinore Fault Zone, on a previously unknown fault structure. There was no surface rupture. It has been proposed that the event occurred on an extension of the recently recognized Puente Hills thrust system. [cite web | last = Shaw | first = John H. | coauthors = Shearer, Peter M. | url = http://structure.harvard.edu/sgat/SGATfault.html | title = A Blind-Thrust Fault Beneath Metropolitan Los Angeles Identified from Seismic Reflection Profiles and Precise Earthquake Locations | publisher = Harvard University Structural Geology and Tectonics | accessmonthday = April 27 | accessyear = 2006]

A magnitude 5.6 [http://earthquake.usgs.gov/regional/states/events/1987_10_04.php] strike-slip aftershock occurred three days later, on October 4, causing additional damage, and one additional death.

Three people died as a direct result of the earthquake. One death was of a Southern California Edison worker buried by a landslide in the Muir Peak area of the San Gabriel Mountains while working with a crew installing the footings for a high tension power tower north of Pasadena, California. Five other deaths are attributed indirectly to the event. About $358 million USD in damage resulted. [cite web | last = Rowshandel | first = B. | coauthors = Reichle, M.; Wills, C.; Cao, T.; Petersen, M.; Branum, D.; Davis, J. | date = April 11, 2006 | url = http://www.consrv.ca.gov/cgs/rghm/loss/index.htm | title = Estimation of Future Earthquake Losses in California | publisher = California Geological Survey | accessmonthday = April 27 | accessyear = 2006]

The Whittier Narrows earthquake along with two other events -- the May 1983 Coalinga earthquake, M6.5, and the January 1994 Northridge earthquake, M6.7 -- brought blind thrusts to the attention of seismologists and policy makers. As a result, other significant blind thrusts have been identified in Southern California.

References

External links

* [http://www.iris.washington.edu/gifs/slides/california_quakes/slideshow/pages/quake4.htm NOAA images of earthquake damage]
* [http://www.data.scec.org/chrono_index/whittier.html Whittier Narrows earthquake] on Southern California Earthquake Center page