A resident surveys the damage to a building that partially crumbled during an earthquake April 5, 2010 in Mexicali, Mexico.
Aftershocks rattled the southwest Mexico-U.S. border on Monday morning in the aftermath of a major earthquake that killed two people, blacked out cities and forced the evacuation of hospitals and nursing homes.
Sunday's 7.2-magnitude quake, centered just south of the U.S. border near Mexicali, was one of the strongest earthquakes to hit the region in decades, shaking at least 20 million people.
It had a shallow depth of 6 miles (10 kilometers). But the human toll was minimal in large part because the energy from the quake moved northwest of Mexicali toward a less populated area, said Jessica Sigala, a geophysicist from the U.S. Geological Survey.
"We were just kind of lucky that the energy went the other way," Sigala said. "With every earthquake, the earth starts moving a certain direction. It started south of Mexicali and the rupture moved northwest."
Geology expert Pat Abbott called the earthquake signficant, saying that the quake is one that could affect surrounding fault lines. Abbott made a comparison to the Haiti earthquake in January, which measured a magnitude 7.0. The incident resulted in more than 200,000 deaths. Sunday's quake was twice as strong, but so far has only been blamed for two deaths.
Building construction has improved in northern Mexico, a region with a history of quakes, said Carlos Valdes, chief of the Mexican National Seismological Service.
"Construction codes prevented more serious damage," Valdes said. "People see that it always shakes and have improved their construction capacity. Then when the construction codes are implemented, there is stricter control, especially in larger structures."
Still, some homes were destroyed in farming communities on the edge of Mexicali, a bustling commercial center along Mexico's border with California where the quake hit hardest, said Javier Ruiz, an inspector with the city's civl protection agency.
One man was killed when his home collapsed, and another died when he into the street in panic and was struck by a car.
Across the border in Calexico, police patrolled streets littered with shattered glass Monday, and a downtown area was closed because of damage.
Scientists measured about 100 aftershocks early Monday morning, said seismologist Kate Hutton at the California Institute of Technology in Pasadena.
At least 100 people were injured in Mexicali, most of them struck by falling objects, and power was out across the city on Monday, said Baja California Civil Protection Chief Alfredo Escobedo said.
Power lines fell, lamp posts were bent and bricks fell from buildings in Mexicali's aging downtown section. Wells crumbled and the waters of the All-American canal spilled into some streets.
All 300 patients were evacuated from the Mexicali General Hospital because of the structural damage to the building, which also was without electricity and water. Some patients were taken to private clinics but others were in tents.
It was unclear how long the emergency generators powering the private clinics could last. Civil Protection Inspector Alan Sandoval said the most critical patients would be transported to hospitals in Tijuana and the coastal town of Ensenada.
Sandoval said the Easter holiday delayed damage assessments for Mexicali, as did landslides that slowed traffic on the toll road into the city.
The parking garage at Mexicali's city hall collapsed but no one was injured.
Scientists said the main earthquake probably occurred on a fault that has not produced a major temblor in over a century. Preliminary data suggest the quake occurred on the Laguna Salada fault, which last unleashed a similar-sized quake in 1892. Since then, it has sparked some magnitude-5 temblors.
In Calexico, California, a city of 27,000 right across the border from Mexicali, the city council declared a state of emergency.
Calexico police Lt. Gonzalo Gerardo said most of the damage occurred downtown, where buildings constructed in the 1930s and '40s were not retrofitted for an earthquake of this magnitude.
"You've got a lot of cracks. You've got a lot of broken glass," he said. "It's unsafe for people to go there."
Rosendo Garcia, 44, was driving his daughter home from work when the quake struck.
"It felt like I was in a canoe in the middle of the ocean," he said, adding that homes in his trailer park were seriously damaged, including one knocked off its foundation.
A home for seniors in Calexico built in the early 1900s was evacuated and its residents moved to a Red Cross shelter. The Fire Department also brought some sick and elderly people to hospitals because of power outages and gas problems.
Strong shaking was reported across much of Southern California. The earthquake rattled buildings on the west side of Los Angeles and in the San Fernando Valley, interrupting Easter dinners. In San Diego, there were reports of shattered windows, broken pipes and water main breaks in private buildings.
If the preliminary magnitude holds it would be the area's largest temblor since the 7.3-magnitude Landers quake hit in 1992, Jones said. There were at least two other 7.2-magnitude quakes in the last 20 years.