2010 Baja California earthquake

The 2010 Baja California earthquake (also known as 2010 Easter earthquake, 2010 Sierra El Mayor earthquake, or 2010 El Mayor – Cucapah earthquake) occurred on April 4 (

The 89-second quake was widely felt throughout northwest Mexico and southern California. It was also the strongest to rock southern California in at least 18 years (since the M 7.3 1992 Landers earthquake), if not longer: the next most recent comparable earthquake—the 1952 Kern County earthquake (M 7.3)—was 58 years earlier. Each of these earthquakes had a similar magnitude, and was also felt across a large swath of North America. Most of the damage occurred in the twin cities of Mexicali and Calexico on the Mexico–United States border.

Geology

The quake originally was believed to have occurred on the Laguna Salada Fault, which is about 60 kilometers (37 mi) to 80 km (50 mi) long and straddles the California–Baja California border.^[6] The active Laguna Salada Fault ruptured in February 1892 with an estimated M_w 7.2 earthquake.^[7][8]

By the distribution of aftershocks and using radar interferometry, the main shock rupture was found to have occurred on a previously unmapped fault in the Cucapah Mountains and beneath the Colorado River Delta. This fault line was named the Indiviso Fault, after the nearby town of El Indiviso.^[9] A liquefaction zone bounded by the Cerro Prieto Fault and the Laguna Salada Fault was observed.^[10]

Timeline

Foreshocks

Mexicali, El Centro, San Diego, Ensenada, and Tijuana are situated in a very active seismic zone and surrounded by important faults. An earthquake of such magnitude had been expected around the fault situated in the southeast of Mexicali.^[11] Before the M_w 7.2 earthquake occurred, the surrounding area had been seismically active in 2009. Several foreshocks began from April 1, 2010, with magnitudes of 3 and 4.^[12][13]

Mainshock

The earthquake measured 7.2 on the

The April 4 quake was the second largest earthquake in Baja California history after the 1892 Laguna Salada earthquake at a magnitude of 7.2–7.8 on the Richter magnitude scale, and was well recorded in Southern California, especially in the Imperial valley.^[7]

Aftershocks

Four aftershocks with a magnitude of at least 5 have been reported; one at a magnitude of 5.2,^[16] one at 5.4,^[17] one at 5.1,^[18] and one at a magnitude of 5.7, all four within one hour. Additionally, a 5.3 aftershock hit the region very close to the mainshock epicenter on April 8, at approximately 9:44 AM local time.^[19] There have been at least nine large aftershocks in total.^[20]

By six hours after the earthquake, more than 90 aftershocks or triggered earthquakes between magnitude 3.0 and 5.1 were recorded in northern Baja California and Southern California.^[21] This included a magnitude 3 event 5 kilometers (3.1 mi) off the coast of Malibu, California.^[6] By the early hours of the following morning, scientists had measured 100 aftershocks.^[22]

Pat Abbott, a professor emeritus of geology at San Diego State University, said, "Any quake of this size seems to pass some kind of threshold where it's large enough to disturb or trigger other faults. In cases like this, that often means increasing stress on other faults, which makes them more prone to movement. The energy seems to be moving northward toward the San Andreas Fault. I don't want to anthropomorphize, but it's like this quake was goading the San Andreas."^[23] It remains to be seen how the 1,300 km (810 mi) San Andreas Fault was affected by these temblors. The southern section of the San Andreas Fault worries scientists, because it has not ruptured in more than 300 years. The region also includes other faults, including the Imperial Fault Zone.^[23]

In the early morning hours of April 10, 2010, an aftershock measuring magnitude 4.4 was felt throughout most of Southern California and Baja California. It was said to have lasted about ten seconds. No injuries or damage were reported. Another aftershock measuring a similar magnitude struck Southern California on the morning of April 11.^[24]

Seismologists in the California Institute of Technology of Pasadena announced a 10 percent chance of another earthquake on the same magnitude (7.3) or greater to strike within the first week, and 5 percent in the rest of the month of April 2010. It also falls on the state of California's Earthquake Preparedness month, as state and FEMA officials urge the state citizens to take preparations, and schools and businesses conduct earthquake drills across the state. The California Geological survey added 50 new faults to its map of faults several weeks after the earthquake.^[25]

Geological field work as of April 5, 2010, by Dr. Thomas Rockwell, professor of geology at San Diego State University, indicates about one meter of right-lateral surface faulting and 0.3 to 0.5 meters of vertical road offset on a fault that is located east of Laguna Salada Fault. Whether or not this is the Cerro Prieto Fault is unclear as of April 5. This is a developing field situation, as geologists are working to locate and measure the lateral extent of the surface faulting.

A strong aftershock with a magnitude of 5.7 occurred on June 14, 2010, at 9:26:58 PM PDT, with an epicenter near Ocotillo in southwestern Imperial County and a focal depth of 5.0 km.^[26][27]

On July 7, 2010, a 5.4-magnitude earthquake, triggered by the April 10, 2010 quake, occurred on the San Jacinto Fault, the most seismically active fault in California, and one of two that exhibited signs of increased pressure following the Mexico quake. It was centered 15 miles (20 kilometers) northwest of the town of Borrego Springs. The main quake in April had transferred stress to fault zones farther north, triggering the aftershock. The quake rattled buildings in downtown Los Angeles, toppled bottles off shelves, and briefly halted rides at Disneyland.

Impact

Mexico

Baja California state capital

The quake was felt for about 40 seconds in Tijuana, Baja California, located 174 kilometers (108 mi) to the west-southwest, where it caused buildings to sway and knocked out power in parts of the city. Families celebrating Easter ran out of the homes.^[37] A falling tree damaged a city water tank.^[20] Rescuers trying to reach Mexicali from Tijuana were slowed by a landslide along the highway.^[33] The earthquake cracked the main aqueduct that carries Colorado River water from Mexicali to Tijuana, causing limitations on the water supply in Tijuana.^[33]

The day after the quake,

• 2019 Ridgecrest earthquakes
• Cerro Prieto Geothermal Power Station
• Lists of 21st-century earthquakes
• List of earthquakes in 2010
• List of earthquakes in the United States
• List of earthquakes in California
• List of earthquakes in Mexico
• Seiche

References

Further reading

• McCrink, T. P.; Pridmore, C. L.; Tinsley, J. C.; Sickler, R. R.; Brandenberg, S. J.; Stewart, J. P. (2011), Liquefaction and Other Ground Failures in Imperial County, California, from the April 4, 2010, El Mayor–Cucapah Earthquake, U.S. Geological Survey Open-File Report 2011–1071, United States Geological Survey

External links

Wikimedia Commons has media related to 2010 Baja California earthquake.

• M7.2 – Baja California, Mexico – United States Geological Survey
• Rupture characteristics of M7.2 Sierra El Mayor (Mexico) earthquake – PhD Y.Fialko
• The International Seismological Centre has a bibliography and/or authoritative data for this event.