M 7.0 - Baja California, Mexico

Tectonic Summary

The April 12, 2012, M 7.0 earthquake of Baja California, Mexico, occurred as the result of shallow transform faulting along the principal plate boundary between the North America and Pacific plates in the Gulf of California. Focal mechanism solutions indicate that rupture occurred on either a left-lateral northeast-striking fault or a right-lateral northwest-striking transform; the latter is consistent with plate boundary motion. At the location of the earthquake, the Pacific plate moves northwest relative to the North America plate at about 46 mm/yr. The plate boundary though the Gulf of California consists of a series of northwest-trending strike-slip (transform) faults that are separated by pull-apart basins. Farther north, this plate boundary system becomes the San Andreas Fault. The April 12th mainshock occurred along a strike-slip segment of the plate boundary.

Historically, this is an area with a high level of seismicity, with six earthquakes of M 6.5+ occurring since 2000. These include the M 6.9 earthquake in Sonora, Mexico, on August 3, 2009, which was 35 km to the northeast of the April 12, 2012, event. The last M 7+ earthquake in the vicinity of the April 12, 2012, event occurred on April 4, 2010 (M 7.2), approximately 35 km south of the Mexico-USA border and 440 km north of the April 12th event. The 2010 earthquake caused at least 2 fatalities and 233 injuries.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)