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2009 December 30 18:48:57 UTC

Earthquake Details

  • This event has been reviewed by a seismologist.
Location32.464°N, 115.189°W
Depth6 km (3.7 miles) (poorly constrained)
Distances35 km (20 miles) SE of Mexicali, Baja California, Mexico
35 km (25 miles) W of San Luis Rio Colorado, Sonora, Mexico
50 km (30 miles) SE of El Centro, California
2160 km (1340 miles) NW of MEXICO CITY, D.F., Mexico
Location Uncertaintyhorizontal +/- 1.8 km (1.1 miles); depth +/- 31.6 km (19.6 miles)
ParametersNph= 20, Dmin=36 km, Rmss=0.39 sec, Gp=205°,
M-type=regional moment magnitude (Mw), Version=8
Event IDci14565620
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Earthquake Summary

Small globe showing earthquakeSmall map showing earthquake

Tectonic Summary

The northern Baja California earthquake of December 30, 2009, occurred on the principal plate boundary between the North America and Pacific plate. At the latitude of the earthquake, the Pacific plate moves northwest with respect to the North America plate at 45 mm/y. The principal plate boundary in northern Baja California consists of a series of northwest-trending strike-slip (transform) faults that are separated by pull-apart basins. The faults are distinct from, but parallel to, the San Andreas fault. The December 30 main-shock occurred near the southeastern end of a strike-slip segment of the plate boundary that coincides with the Imperial fault, and the focal-mechanism of the earthquake is consistent with the shock having occurred on the Imperial fault. To the south of the region of the earthquake, the principal plate boundary changes from the Imperial fault to the strike-slip Cerro Prieto fault, which is sub-parallel to the Imperial fault but offset from it to the southwest. The pull-apart basin between the two northwest-trending strike-slip faults is a region of high heat flow and frequent earthquakes. Earthquakes having magnitudes as high as 7.1 have been historically recorded from the section of the Pacific/North American plate boundary on which the December 30, 2009, earthquake occurred.

USGS Podcast Interview: Ken Hudnut, Southern California Regional Coordinator for the USGS Earthquake Program, spends a few minutes filling in some details about this event.