[Updated at 9:50 p.m.] Read the full CNN.com story
[Updated at 9:18 p.m.] The tsunami watches have been canceled for "all areas of the Indian Ocean," according to the Pacific Tsunami Warning Center.
[Updated at 9:12 p.m.] Residents in Banda Aceh said they were without power.
Residents in coastal towns fled inland to higher ground just after the quake, according to a local radio station.
The tsunamis, in Banyak Island and Teluk Dalam, were small and not dangerous, measuring just under a foot high, said Fauzi, chief of the Indonesian Meteorological and Geophysics Agency. Fauzi goes by only one name, which is common in Indonesia.
[Updated at 8:20 p.m.] The quake triggered two tsunamis, according to the Indonesian Meteorological and Geophysics Agency.
There were no immediate reports of damage or injuries. The initial shaking, which reportedly lasted for at least three minutes, prompted scores of people to run out of buildings into open air, witnesses said.
"The quake was felt quite strong, maybe about three four minutes," said Dadik, the head of Simeulue police who goes by only one name. "I've ordered my staff to check if there's any damage or casualties, but apparently no damage reported so far."
Measurements of sea levels indicated that tsunami waves "may have beenÂ destructive along coasts near the earthquake epicenter," the Pacific TsunamiÂ Warning Center said.
One registered tsunami measured close to a foot from peak to trough andÂ was considered a small tsunami, said geophysicist Gerard Fryer with the PacificÂ Tsunami Warning Center.
Indonesia announced the tsunami warning quickly, Fryer said, andÂ officials at Indonesia's Meteorological and Geophysics Agency lifted it aboutÂ two hours later.
[Updated at 10:48 p.m.]Â The quake was the largest in the Baja California and Southern California area since 1992, the USGS reported.
The '92 quake, which struck in Landers, California, triggered an earthquake the next day in Nevada and another quake 11 days later in Southern California, according to USGS seismologist Lucy Jones. Both were 5.7-magnitude quakes.
[Updated at 10:30 p.m.]Â The USGS has a feature on its Web site where you can respond if you felt the quake. Thus far, there are hundreds of responses with peopleÂ claiming to have experienced the earthquake, representing areas in California and Mexico, to Arizona and Nevada.
Meanwhile, Twitter has thousands of posts about the quake. Posts â€“ at different times â€“ are trending under several topics, including: â€śUSGS,â€ť â€śEarthquake,â€ť â€śMexico,â€ť Mexicaliâ€ť and â€śBaja California.â€ť
Some are weighing in with their first brushes with an earthquake; others are posting about some of the quakeâ€™s effects, such as people they know getting trapped in elevators.
There is even a bit of wry humor. A poster with the name jfranke24 wrote: â€śEarthquake rumbles through SoCal while we're eating dinner next to the Staples Cntr. You know you're in LA when everybody claps afterwards.â€ťÂ
[Updated at 10:00 p.m.]Â CNN's Ted Rowlands reports from Los Angeles, California:
[Updated at 9:40 p.m.]Â At least one person has been confirmed killed in a building collapse in Mexicali, according to the assistant director of civil protection in Tijuana. There have also been reports of injuries and structural damage, according to Alfredo Escobedo, Mexico's director of civil protection.
Pictures from Mexicali showed the sides ripped off buildings, toppledÂ telephone poles, cracked roads, and supermarket aisles strewn with food thatÂ had fallen off shelves.Â In California and Arizona, there were no immediate reports of injuries and only limited reports of damages. Residents across southern California and Arizona reported serious groundÂ shakes.
[Updated at 9:33 p.m.]Â During a press conference earlier this evening, Lucy Jones, a seismologist with the USGS, said someÂ magnitude 5 or magnitude 6 aftershocks were possible during the next few days.
[Updated at 8:52 p.m.]Â There have been three large aftershocks so far, including one that registered a 5.5 magnitude, and other smaller temblors, USGS said.