According to reports, Mexicali and adjacent cities are experiencing widespread power outages and buildings are suffering from major structural damage. Escobedo said that at least 100 people were injured, most of them struck by falling objects. Mexicali felt at least 20 aftershocks, and the city is under a virtual blackout without viability to regain power for approximately 14 hours.
The quake was one of the strongest to hit Southern California in decades, and high rise buildings in Los Angeles and San Diego rocked back and forth when it hit. There were reports of shattered windows, broken pipes and water main breaks in private buildings in San Diego, but there were no reports of injuries.
Preliminary USGS information indicated the epicenter was 19 miles southeast of Mexicali, at an area that has been rocked with magnitude 3.0 quakes all week.
The quake was followed by a series of strong aftershocks including one of magnitude-5.1 was felt in the Imperial County desert east of San Diego within an hour of the main quake. Magnitude-4.5 and magnitude-4.3 aftershocks came before and after the quake. According to CalTech seismologist Lucy Jones, a 6.0-magnitude aftershock is reasonably likely.
"Don't be surprised if you feel something in the next few days," said Jones at a Sunday news conference. "We need to remember that every earthquake we have has the possibility of triggering another earthquake."
Jones estimated that at least 10 million people felt the earthquake and that most of Southern California felt it at some level.
The quake knocked out power to 346 California Edison customers in Rancho Palos Verdes. Customers in Huntington Beach, Montebello and Compton reported having "flickering lights."
According to Jennifer Ramp of San Diego Gas & Electric, nearly 2,400 customers lost power in Dana Point, just inside the Orange County line. In San Diego County, more than 600 customers lost power in Borrego Springs when the earthquake struck, Ramp said. Utility officials said that all Southern California residents who experienced any power interruption regained it within minutes.
The Los Angeles Department of Water and Power says there are no power outages anywhere in the city, spokeswoman Maryanne Pierson said.
USGS officials said the quake was felt as far north as Santa Barbara and as far east as Las Vegas. Strong shaking was also reported in Coachella Valley and Riverside.
The Los Angeles City Fire Department was on emergency earthquake status and assessed their districts and reported no serious damage or major injuries.
According to Disneyland security, all of their rides were shut down after the quake. There were initial reports of people being trapped in elevators at the nearby Disneyland Hotel, but those reports were false. All attractions were back open and running in normal condition by 7:30 p.m.
Minor damage has been reported from Baja California. Tijuana Fire Chief Rafael Carillo says firefighters were rescuing people trapped in a hotel elevator. He says firefighters so far have responded only to reports of minor damage.
On the U.S. side of the border, officials say the damage is piling up in Calexico as the day wore on. Authorities said that most of the damage occurred in downtown Calexico where buildings that were constructed in the 1930s and '40s and not retrofitted for an earthquake of this magnitude.
Due to such construction, many buildings are in partial or full collapse. Throughout the city, fires sprouted up due to short-circuited electrical wires. About two dozen injuries were reported. Most were minor, but there were some broken limbs due to collapsed buildings.
The Calexico Fire Department had only eight people on duty due to the Easter holiday, but everyone was quickly called in after the quake.
"There was substantial damage down to our most oldest part of town," said Calexico Fire Chief Peter Mercado. "We had our hands full for the last few hours but we're trying to sustain and stabilize and really get a good grasp as for the damage but we won't have a good idea until tomorrow morning."
One San Diego man said he and his family drove to Calexico and were waiting for his mother-in-law to walk across the border from Mexicali to join his family for Easter dinner when the quake hit.
"It was tremendous. It was a very scary experience. You can hear everything shaking, dust falling off buildings, people screaming and running out of house," said Frank Moreno. "I immediately ran out because I've been in earthquakes before and I don't stand around for everything. I forget about family and everything. I just run to the open areas."
Near the epicenter, receptionist Juan Carlos Fernandez says there was minor damage at the Crowne Plaza hotel in Mexicali. The damage includes broken pipes and windows.
A Mexicali viewer described the scene as hectic with toppled homes, stores and other buildings in addition to ruptured gas and water lines. Another viewer with family in Mexicali said that he was relieved to reach his family, but his sister and parents say their home is completely destroyed and that they need to find a place to sleep. They added that they are afraid to sleep in any buildings, for fear of aftershocks.
Sunday's temblor is expected to be California's largest since the 7.3-magnitude Landers quake that hit in 1992.
AP contributed to this report.