LOS ANGELES -- The strongest earthquake in 40 years and a second, less powerful quake rumbled through Southern California early yesterday, killing a 3 1/2 -year-old boy, injuring more than 170 people, and damaging homes and businesses in desert and mountain communities east of Los Angeles.
The quakes crumbled buildings, ignited fires, triggered giant landslides and buckled highways, officials said. In Los Angeles, about 100 miles west of the quake zone, residents were shaken awake by the strong, rolling quake, which knocked out power to about a half-million customers.
After surveying the region by helicopter, Gov. Pete Wilson declared a state of emergency in the counties of Riverside and San Bernardino.
"My house is destroyed," said San Bernardino County firefighter Bill Emmett, stationed near the epicenter of the first quake. "It picked up cars and threw them around. I think California just lost a resident."
The earthquakes were centered near Yucca Valley, a remote stretch of the Mojave Desert, and Big Bear Lake. Both are east of Los Angeles.
The first temblor, dubbed the Landers quake because it occurred near that tiny town 26 miles northeast of Palm Springs, hit at 4:58 a.m.
PDT. It was felt as far away as Denver, Phoenix and Boise, Idaho. It measured 7.4 on the Richter scale, according to the U.S. Geological Survey in Golden, Colo.
The second quake, about three hours later, was centered near Big Bear Lake in the San Bernardino Mountains, about 20 miles west of the first temblor. It was measured at magnitude 6.5 and caused extensive damage to the mountain ski resort at the lake.
Seismologists had reported a series of small earthquakes just before midnight Saturday. The Landers quake occurred along the same fault line as a 6.4-magnitude quake on April 22, and scientists said the earlier temblor was a precursor to the one that hit at dawn yesterday.
The quakes occurred on the one-year anniversary of the 5.8-magnitude Sierra Madre temblor. Residents could not help but recall how their community was left in ruins.
"We're still recovering, and this is quite a reminder," Sierra Madre City Councilman George Maurer said.
"It is almost within two hours of exactly a year. It is really amazing," said Ken Cromeenes, business administrator of the Sierra Madre Congregational Church. The first quake hit as the church choir was singing the "Battle Hymn of the Republic."
While metropolitan Los Angeles sustained little damage, the desert communities of Yucca Valley and Joshua Tree, located six miles south of the epicenter of the Landers quake, appeared to be hit hardest.
The 3 1/2 -year-old victim, Joseph Bishop, was crushed by a collapsing fireplace in Landers, near Joshua Tree National Monument and Twentynine Palms Marine base, police said. The boy, from Massachusetts, was visiting his father.
Hi-Desert Medical Center in Joshua Tree treated dozens of people for earthquake-related injuries, including severe cuts, bone fractures and shortness of breath, said Theresa Graham, a hospital spokeswoman.
Big Bear Community Hospital was treating at least 40 earthquake-related injuries, a spokeswoman said.
All told, 171 people were hurt, said Cheryl Huff, a San Bernardino County sheriff's deputy.
Fires were reported at several mobile homes in Landers. Water pipes ruptured, and afterward people lined up at a liquor store to buy ice and bottled water. A bowling alley in Yucca Valley partially collapsed, and the roof of the local K mart store caved in, police said.
The Big Bear quake lasted 45 seconds and emanated from a different fault, about 10 miles west of Joshua Tree, but near the San Andreas Fault -- considered the most dangerous fault in California.
Annette Welch, with VoCommCommunications in Big Bear, said the quake caused major structural damage and rock slides in the area, forcing the closure of roads.
The San Bernardino Sheriff's Department reported that the quake downed telephone lines in the Big Bear area, while rock slides forced the closure of Highway 18 and Highway 38.
Late in the afternoon, Kerry Sieh, a seismologist from Cal Tech, who was inspecting the area from a helicopter, found that the ground had moved 18 feet in one place on the fault 43 miles north of Landers.
"Beyond Landers, all hell breaks loose," Mr. Sieh said. He added that numerous faults come close to the surface in the area and several had broken.
The U.S. Geological Survey's Earthquake Information Office in Golden, Colo., classified the 7.4 quake as a "major" event, and it was described as a strike-slide earthquake producing a horizontal-type movement of the earth.
The Landers quake was the fourth-largest in California this century and the most severe one since July 20, 1952, when a 7.8 magnitude jolt rocked the Tehachapi-Bakersfield area in Central California.
By comparison, the first quake yesterday was nearly three times as powerful as the Loma Prieta earthquake measuring 7.1 that hit the San Francisco area in October 1989.
No major damage was reported in the Los Angeles area from either temblor, although there were sporadic power outages from the first one that left about 51,000 people without electricity, officials said.
"We were very lucky," said Los Angeles Police Department Capt. David Kalish.
He said Chief Willie Williams, who began his first day yesterday at the helm of the Los Angeles Police Department, was in contact with the emergency operations center.
"Welcome to California, Chief Williams," Captain Kalish quipped.