A magnitude-4.1 aftershock hit parts of Southern California on Saturday afternoon, the largest of more than a hundred such aftershocks of Friday night's magnitude-5.1 earthquake that shook homes and businesses throughout Los Angeles and Orange counties.
The 4.1 temblor struck just after 2:30 p.m., according to the U.S. Geological Survey, which also recorded two foreschocks Friday, measuring magnitudes of 3.6 and 2.1.
The magnitude-5.1 earthquake centered just east of La Habra on Friday night was felt throughout the region, however the damage it caused was primarily isolated to a pocket of northern Orange County, where 26 homes were red-tagged, officials said.
Dozens of aftershocks continued to rumble through the night, including one measured at magnitude 3.6 at 9:30 p.m. Friday, and another measured at magnitude 3.4 at 9:02 a.m. Saturday, according to the USGS.
And more are expected, USGS Geophysicist Doug Given said.
"We anticipate there will be a few more," he said.
"This is fairly typical aftershock activity for an event this size," Given said. "This is maybe a little on the energetic side."
Over the next seven days, "We have been saying there is about a 5 percent chance of a larger earthquake to come," he said. "But that chance is front-loaded."
As time passes, large aftershocks become increasingly less likely to occur, he explained. "That likelihood is decaying very rapidly."
The quake rattled windows and nerves throughout Orange and Los Angeles Counties, but Fullerton was hardest hit by the quake.
As officials made damage assessments overnight and into Saturday, 20 apartment units and six houses in Fullerton were deemed uninhabitable and red-tagged, Fullerton police Sgt. Mike Chlebowski said.
Residents would not be allowed to reoccupy the homes until they were checked out by an inspector, he said.
And work on a ruptured water main at Rosecrans Avenue and Gilbert Road Street continued to force a road closure Saturday morning, Chlebowski said.
But no earthquake-related injuries had been reported Saturday, in Fullerton or elsewhere.
La Habra had been spared an significant structural damage, La Habra police Lt. Kyle Davis said. "It all seems cosmetic at this point."
No buildings had been red-tagged, though a couple dozen La Habra residents had evacuated their homes voluntarily due to safety concerns, Davis said.
Authorities had initially feared possible structural damage at three apartment buildings that were especially rocked by the quake in the 2500 block West Whittier Boulevard, the 400 block of North Idaho Street and the 700 block of West First Avenue, Davis said.
Considering how close La Habra lies to the earthquake's epicenter, "We fared pretty well," he said.
"The La Habra Police Department has received multiple reports of broken windows throughout the community, with some areas reporting natural gas smells," La Habra city officials said in a written statement.
"Gas was shut off in the 1200 block of (South) Beach (Boulevard), as a precautionary measure. LA Fitness, which is located in one of the shopping complexes near the intersection of Imperial (Highway) and Beach (Boulevard), had water running off the roof. At Beach (Boulevard) and Lambert (Road), the traffic signal was hanging precariously, but it has since been removed.
Reports of natural gas leaks were also widespread in Rowland Height, Los Angeles County Fire Department officials said.
A ruptured pipe caused water to flow from the ceiling of a Rite Aid Pharmacy along Colima Road, but the issue was handled within about 20 minutes, Los Angeles County Fire Department Dispatch Supervisor Cheryl Sims said. Officials had previously reported the incident as occurring at a pharmacy along Nogales Street.
Near Brea, a rockslide along Carbon Canyon Road was blamed for causing a car to overturn, Brea police said. The crash resulted in only minor injuries, however the roadway near the county line remained closed Saturday.
The Red Cross set up an evacuation shelter at the La Habra Community Center, 101 W. La Habra Boulevard, where 38 people spent the night, Red Cross spokeswoman Meredith Mills said. It remained open through Saturday morning.
"We're definitely here to help people if they need it," Mills said.
A preliminary survey found "no significant reports of damage" in Los Angeles County, according to a statement issued by the Los Angeles County Office of Emergency Management.
Los Angeles County's bridges and other infrastructure were also free from reported damage Saturday, Los Angeles County Department of Public Works officials said.
Friday's earthquake was believed to be associated with the far east end of the Puente Hills Thrust fault system, Given said. "This is the fault system that, on its northern edge, was responsible for the Whittier Narrows Earthquake in 1987," Given said. Prior to the Whittier Narrows earthquake, the fault system had been unknown.
Scientists in Pasadena had a four second warning before the shaking reached them from the La Habra area thanks to an experimental early warning system that's been in operation for two years, Givens said.
Givens said he hoped increased funding on the federal and national levels would soon help bring the technology to the mainstream, as has been done in Japan and Mexico City.
About 200 Southern California Gas Company customers remained without service Saturday morning as crews rushed to fix leaks and restore service to customers whose gas was shut off my earthquake valves, according to the utility. Those who suspect a natural has leak were advised to leave the area immediately and report the leak by calling 800-427-2200.
Southern California has not experienced a devastating earthquake since the 1994 magnitude-6.7 Northridge quake killed several dozen people and caused $25 billion in damage.
Preliminary data suggest Friday night's 5.1 magnitude earthquake occurred near the Puente Hills thrust fault, which stretches from the San Gabriel Valley to downtown Los Angeles and caused the 1987 Whittier Narrows earthquake, USGS seismologist Lucy Jones said.
"It's a place where we've had a lot of earthquakes in the past," she said.
The 5.9 Whittier Narrows quake killed eight people and caused $360 million in damage.
Hall of Fame announcer Vin Scully was on the air calling the Angels-Dodgers exhibition game in the sixth inning at Dodger Stadium when Friday's quake occurred.
"A little tremor here in the ballpark. I'm not sure if the folks felt it, but we certainly felt it here in press box row," Scully said. "A tremor and only that, thank goodness."
Tom Connolly, a Boeing employee who lives in La Mirada, the next town over from La Habra, said the magnitude-5.1 quake lasted about 30 seconds.
"We felt a really good jolt. It was a long rumble and it just didn't feel like it would end," he told The Associated Press by phone. "Right in the beginning it shook really hard, so it was a little unnerving. People got quiet and started bracing themselves by holding on to each other. It was a little scary."
Friday's quake hit a week after a pre-dawn magnitude-4.4 quake centered in the San Fernando Valley rattled a swath of Southern California. That jolt shook buildings and rattled nerves, but did not cause significant damage.
Givens said that quake was not associated with the same fault system believed responsible for Friday's earthquake near La Habra.
Officials throughout the region said the earthquake was a stark reminder for California residents to be prepared for earthquakes with supplies and plans.
"Clearly we cannot predict earthquakes, we can only say things about the statistics of earthquakes," Given said. "Based on the best science of the faults and the earthquake history in Southern California, in the Los Angeles region, there's a 97 percent chance in the next 30 years of a magnitude 6.7 or larger."
The Associated Press contributed to this report.