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Event (non-earthquake) on April 4, 2006, ~9AM PST

Locating the Source of the Shake, Rattle and Roll



At ~9AM on April 4th 2006 a disturbance described as a ‘boom’, ‘jolt’, and ‘whack’ was felt throughout the southern California region. A team of seismologists from Scripps Institution of Oceanography investigated possible origins and causes of this event and determined it was not seismic (i.e., not caused by an earthquake). Using information from the seismic network in Southern California Elizabeth Cochran (a post-doctoral researcher working with Peter Shearer) used a grid search method to determine that the origin of this event was likely ~120 miles off the San Diego coast. This location was also consistent with similar analyses preformed by Robin Matoza, Kris Walker, Michael Hedlin and Catherine de Groot-Hedlin. This source generated a wave that traveled at ~320 meters per second, roughly the speed that sound travels through the air.

This 3D interactive visualization includes the likely origin of the sound wave (orange sphere) with associated error ellipses, locations of seismic stations in southern California that have an observable record of the sound wave (red cubes) and those that do not (white cubes), the location of ~34,000 earthquakes (pink spheres) recorded over the past 20 years by the ANZA seismic network. Also shown are known fault traces (brown lines), roads (purple lines), topography of the region (shaded relief) and the Salton Sea (dark blue).


Links to websites:
http://www.signonsandiego.com/news/metro/20060427-9999-1n27boom.html
http://www.signonsandiego.com/news/metro/20060423-9999-1n23bigboom.html
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