April 4, 2010 Earthquake: Baja California, Mexico

Two people killed, at least 233 injured and many buildings damaged (VII) in the Mexicali area. Felt (VII) at Guadalupe Victoria and (V) at El Sauzal, Ensenada, Maneadero, Primo Tapia, San Felipe, Tecate and Tijuana. Felt (VI) at San Luis Rio Colorado, Sonora. Felt in much of Baja California and northwestern Sonora and as far as Aguascalientes, Ciudad Juarez and La Paz. About 28 km of surface faulting observed on the Borrego Fault southwest of Mexicali. Many buildings damaged (VII) at Calexico and Imperial, California. Felt (VII) at El Centro and Heber; (VI) at Brawley, Calipatria, Holtville and Ocotillo; (V) at Borrego Springs, Boulevard, Campo, Chula Vista, Coachella, Coronado, Jacumba, Lemon Grove, Los Angeles, Niland, Pine Valley, San Diego, San Ysidro, Tecate, Thermal, Westmorland and Winterhaven. Felt (V) at Somerton, Wellton and Yuma, Arizona. Felt throughout southern California, in much of Arizona, in the Henderson-Las Vegas area, Nevada and in parts of New Mexico and Utah.

The April 4, 2010, M 7.2 Baja California Sierra El Mayor earthquake occurred as the result of shallow strike-slip faulting in northern Baja California, approximately 65 km south of the Mexico-USA border along the principal plate boundary between the North America and Pacific plates. Focal mechanism solutions indicate that rupture occurred on either a left-lateral northeast-southwest-striking fault or a right-lateral southeast-northwest-striking fault. At the location of the earthquake, the Pacific plate moves northwest relative to the North America plate at a velocity of about 46 mm/yr.

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, strands of the San Andreas Fault system. The April 4th main-shock occurred along a strike-slip segment of the plate boundary that coincides with the southeastern part of the Laguna Salada fault system. This complex event may have begun with east-down motion along faults on the eastern edge of the Sierra El Mayor, then progressed to the northwest with oblique slip, that is, a combination of lateral shift to the right and also east-down motion. Overall, the location and focal mechanism solutions of the earthquake are consistent with the shock having occurred on this fault system. Field geologists from the Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California (CICESE, written commun., 2010) observed surface rupture associated with the 2010 event at latitude 32.578621°, longitude –115.725814°. Highway 2 was offset at this location by a total of about 1.2 m across a zone of fractures that offset the road towards the right, with the east side also dropping downward. Aftershocks appear to extend in both directions along this fault system from the epicenter of the April 4, 2010, event. The aftershock zone extends from near the northern tip of the Gulf of California to 10 km northwest of the Mexico-USA border.

Historically, this is an area with a high level of seismicity, though the April 4th event is the largest earthquake to strike the area since 1892. The April 4th earthquake was larger than the M 6.9 earthquake in 1940 or any of the early 20th-century events (for example, 1915 and 1934) in this region of northern Baja California. The 1892 earthquake occurred along the Laguna Salada fault system, but surface offsets associated with the 1892 event lie farther northwest than the April 4th mainshock’s epicenter. The 2010 event’s aftershock zone extends to the northwest, overlapping with the portion of the fault system that is thought to have ruptured in 1892. The 1940 Imperial Valley earthquake approached M 7, though it occurred farther to the north and on the Imperial fault. Both the 1892 and 1940 earthquakes were associated with extensive surface faulting. An event of M 7.0 or 7.1 occurred in this region in 1915, and then a M 7.0 to 7.2 event in 1934 ruptured the Cerro Prieto fault with up to several meters of surface slip.

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)

Felt Reports

Two people killed, at least 233 injured and many buildings damaged (VII) in the Mexicali area. Felt (VII) at Guadalupe Victoria and (V) at El Sauzal, Ensenada, Maneadero, Primo Tapia, San Felipe, Tecate and Tijuana. Felt (VI) at San Luis Rio Colorado, Sonora. Felt in much of Baja California and northwestern Sonora and as far as Aguascalientes, Ciudad Juarez and La Paz. About 28 km of surface faulting observed on the Borrego Fault southwest of Mexicali. Many buildings damaged (VII) at Calexico and Imperial, California. Felt (VII) at El Centro and Heber; (VI) at Brawley, Calipatria, Holtville and Ocotillo; (V) at Borrego Springs, Boulevard, Campo, Chula Vista, Coachella, Coronado, Jacumba, Lemon Grove, Los Angeles, Niland, Pine Valley, San Diego, San Ysidro, Tecate, Thermal, Westmorland and Winterhaven. Felt (V) at Somerton, Wellton and Yuma, Arizona. Felt throughout southern California, in much of Arizona, in the Henderson-Las Vegas area, Nevada and in parts of New Mexico and Utah.

Tectonic Summary

The magnitude 7.2 northern Baja California earthquake of Sunday April 4th 2010, occurred approximately 40 miles south of the Mexico-USA border at shallow depth along the principal plate boundary between the North American and Pacific plates. This is an area with a high level of historical seismicity, and also it has recently been seismically active, though this is the largest event to strike in this area since 1892. Today's earthquake appears to have been larger than the M 6.9 earthquake in 1940 or any of the early 20th century events (e.g., 1915 and 1934) in this region of northern Baja California. (reference #1053)

No injuries were reported in Calexico, the U.S. area hardest hit by the 7.3-magnitude quake. A 3-block-by-4-block area containing prewar buildings housing businesses was closed because of damage. "There's broken windows, some cracked masonry buildings" and some buildings had falling bricks, although none was in immediate danger of collapse, police Lt. Jesus (hay-SOOS') Serrano said. Sunday's quake centered just south of the U.S. border near Mexicali killed two people in Mexico and injured at least 100, including someone who was hit in the head by a sign at a carwash in the California town of El Centro. The initial earthquake downed three power lines, a gas leak forced a brief evacuation of about 30 homes, and residents were removed from a senior living center built in the early 1900s. Electricity was out for hours in the city's southeast area. The U.S damage appeared to be limited to California's southeastern Imperial Valley in what was one of the strongest earthquakes to hit the region in decades. The shaking was felt hundreds of miles away in Phoenix and Las Vegas. (reference #6979)

2010, April 4. Two killed, 25232 affected, $1150 million damage. (reference #1250)

The Magnitude 7.2 El Mayor Cucapah Earthquake (also known as the Sierra El Mayor Earthquake) of April 4, 2010, was in Northern Baja California at the former mouth of the Colorado River. This event shook not only Mexicali and Tijuana but also a large part of Southern California and parts of southwestern Arizona and Nevada. There were two confirmed deaths in Mexicali and 100 persons were injured between Baja California and Imperial County California. The total estimated damage in Southern California from the El Mayor-Cucapah event was $91 million while the total estimated damage between Southern California and Baja California was estimated to be $1 billion with most of the damage affecting the agriculture industry and irrigation district in Baja California. (reference #https://www.ngdc.noaa.gov/hazel/view/reference/data?authorInclude=cal%20oes)

$91 million in economic loss in U.S., $950 million in economic loss in Mexico. 4 deaths in Mexico (reference #13727)