2 Strong Quakes Jolt Wide Area : 7.4 Desert Temblor Is Sharpest in 40 Years : Tremors: The shock in Yucca Valley is followed by a 6.5 jolt at Big Bear Lake. A child is killed and 171 people are injured. Slides block highways and a power blackout affects at least 550,000.

YUCCA VALLEY, Calif. —  Two strong earthquakes and dozens of powerful aftershocks shook Southern California awake Sunday, causing one death and 171 injuries in the San Bernardino County desert and mountains but mostly sparing the urban sprawl from damage.

The violent temblors, which jostled skyscrapers as far away as Denver, ruptured the ground and buckled roadways in the high desert north of here. Residents in remote towns were left without water, and rockslides that blocked highways stranded vacationers in the Big Bear and Lake Arrowhead areas.

Power blackouts affected more than 550,000 people around the region, and downed power lines sparked about two dozen fires.

The first shaker struck at 4:58 a.m. in a rural area six miles north of Yucca Valley, a small desert community nestled along California 62 outside Joshua Tree National Monument. Rousing Sunday morning sleepers from northern Mexico to San Luis Obispo, the magnitude 7.4 quake was the strongest in California in 40 years and almost three times the strength of the destructive Bay Area earthquake of 1989.

Three hours later, a magnitude 6.5 temblor centered east of Big Bear Lake unleashed a new round of tremors, causing slides that temporarily trapped motorists and shrouded the San Bernardino Mountains in a massive dust cloud. Seismologists said it was on a different fault but may have been triggered by the earlier quake.

As strong aftershocks to both quakes continued through the morning, the state Office of Emergency Services issued an unprecedented advisory urging people to stay off freeways and curtail activity. Scientists called the event a “major earthquake sequence” and state authorities asked local governments to remain on alert.

After surveying the stricken region by helicopter, Gov. Pete Wilson declared a state of emergency in the counties of Riverside and San Bernardino. The declaration allows cities and counties to apply for state funds to make repairs.

Asked whether the state budget crisis will hamper the availability of funds, Wilson said: “We’ll provide the help first and worry about that later.”

Although major damage and injuries were confined to the remote desert and mountain towns near the epicenters, the temblors were the news du jour across Southern California Sunday. Some people stayed glued to their televisions for the continuing broadcasts mounted by all three networks, while others toted radios to the beach to stay abreast of the story.

Everybody had a tale to tell, especially the region’s shaken tourists--300 of whom were evacuated from the Disneyland Hotel in Anaheim.

“It was like being on top of a mast in a sailboat,” said Gerry Zemojtel, 38, of Tacoma, Wash., one of the evacuees. “When I went to grab my baby out of the crib, I reached in and he rolled by and I missed him.”

The morning’s first quake landed its toughest punch on the string of rustic towns that straddle California 62 east of Palm Springs--Morongo Valley, Yucca Valley and Joshua Tree, all of which suffered damage in a 6.1-magnitude quake just two months ago.

In Sunday’s shaking, the wall of a bowling alley and the roof of a K Mart in Yucca Valley collapsed, mobile homes were tossed off their foundations, water mains were snapped and four dwellings were destroyed or badly damaged by fires.

The town’s main supermarket and numerous other businesses closed because of damage and toppled goods, and the lone fatality directly linked to the quake occurred in Yucca Valley when a 3 1/2-year-old boy was crushed by falling bricks. The toddler, Joseph Bishop, was asleep near a living room chimney when the bricks fell on him, authorities said.

“We lost a member of our family, a loved one,” said the child’s father, who declined to give his name or discuss the circumstances surrounding the boy’s death.

Friends of the family said the child’s parents, who live in Newbury Port, Mass., were visiting their hometown and staying with friends while attending a 20th reunion at Yucca Valley High School. Two other children were asleep in the living room but escaped serious injury.

Hi-Desert Medical Center in Joshua Tree treated 94 people for minor injuries. Twelve people were hospitalized.

Desert residents described the quake as a long, terrifying ride that was dramatically stronger and sharper than the temblor they experienced on April 23.

“It was like someone picked me up out of bed and threw me on the floor,” said Cindy Ness of Yucca Valley. “Every time I tried to get up it threw me back down again. Everything in the room was crashing down around me.”

Sipping coffee on her front lawn Sunday morning, an edgy Edie McDowell said her house “shook like mad--back and forth and back and forth, incredible contortions.” The force of the quake uprooted a toilet in her son’s home and toppled all his fish tanks.

“I am scared to death,” McDowell said, adding that she planned to “grab my sleeping bag” and spend Sunday night on the grass outside.

North of the epicenter, the desert hamlets of Landers and Flamingo Heights weathered some of the worst shaking--and had some of the most dramatic evidence of the earth’s gyrations. The main highway through town, California 247, suffered deep craters and three-foot-wide cracks. Buckling and fissures were visible in many side roads as well.

The shifting soil also left long, dramatic furrows in the desert sand, yanked porches off of homes and businesses and shifted chain-link fences.

“It was like a freight train coming through the house,” said Susan Reynolds. “All I knew was I had to get the kids and get out. The house is trashed.”

The biggest problem confronting Landers and Flamingo Heights was water. Tremors ruptured the towns’ 250,000 gallon water tank and snapped numerous distribution pipes, leaving residents scouring for supplies as the noon hour arrived and the desert temperature topped 100.

Fred Nokes, 57, stopped by the tiny Landers post office in hopes of finding some water, but struck out: “I guess I’ll have to drain my water heater,” Nokes said as he climbed back in his battered pickup truck.

San Bernardino County Supervisor Barbara Riordan, who represents Yucca Valley, said the National Guard may be asked to truck in water to make up for the interruption in service. The U.S. Marine Corps donated one truck for such use on Sunday, and residents were sharing their own reserves.

Sunday’s second earthquake, which struck at 8:04 a.m., wreaked havoc in the mountain resorts near Big Bear Lake. A popular tourist attraction, the region was hosting about 100,000 visitors Sunday--including 3,000 vacationers attending the Big Bear Scottish Festival and Games, which was canceled.

“The party’s over,” lamented Big Bear City Councilman Bill Dwyer. “We must have had half a dozen major events going on up here and every single one has been disrupted.”

City-owned buildings were unscathed, Dwyer said, but at least four commercial buildings in Big Bear suffered major structural damage. In addition, the Community Market near the lake’s east end burned to the ground and entire blocks of buildings along the lake’s main boulevard were damaged when their brick or stone chimneys pulled loose and crumbled.

More than 50 people sought treatment at Bear Valley Community Hospital, and the injuries quickly overwhelmed the small, 28-bed facility, said chief executive officer Jon D. Smiley. The hospital was forced to add beds from other locations to supplement its emergency room, and 10 vacationing doctors and nurses volunteered their help throughout the day.

Patty Reynen, who came for treatment of a twisted ankle, said she was in the office of the 200-unit condominium complex she manages at the Snow Summit ski resort when the second quake hit.

“My husband was just saying to calm down--that it’s all right now,” Reynen said. “Then it started shaking again. I was just going down the staircase and I got pitched out the door. I landed face first.”

At Big Bear City Park, 150 people set up a temporary encampment, raising tents, creating make-shift canopies out of blankets and stocking up on food, barbecues, ice coolers and clothing.

One of the campers, Heidi Miller, was thrown to the ground when she attempted to run out of her house during the second quake. She said her home is a shambles and believes the cracked chimney will tumble if another strong jolt strikes.

“Everything was demolished,” Miller said of her Big Bear City house. “This family got out and is going to stay out.”

At the 75-room Big Bear Inn, the temblor interrupted a Rossini Music Festival and forced the evacuation of 25 guests. The tremors activated the hotel sprinkler system, causing water damage throughout the three-story building and destroyed some irreplaceable artworks--including a 17th-Century Japanese vase, said executive manager Sheila Moore.

The temblors caused vacationing “flatlanders” to make an early exodus from the mountains Sunday, and they were joined by many year-round residents who packed up and get out.

Laurie Passarella, a resident of Big Bear City who is due to deliver a baby in three weeks, intended to flee to her sister’s in Burbank, but feared that more shaking may follow.

“That’s why I’m getting out of here,” Passarella said. “I would be alone all week and I don’t want to be here for the aftershocks.”

Initially, however, Passarella and others found all roads leading from Big Bear either partially or completely shut down--blocked by rockslides. In the hours immediately after the quakes, California Highway Patrol officers escorted travelers around the pavement bulges and mounds of rubble, but the going was slow and precarious.

In one odd road scene, hundreds of new and classic Corvettes were snaking down California 18--a back exit into Lucerne Valley--cutting short a weekend convention of classic Corvette owners.

Elsewhere in Southern California, there were scattered injuries--mostly chest pains, cuts and sprains--as well as power outages and minor fires that were quickly contained.

Airports throughout the region continued to operate normally, but Amtrak canceled seven trains on the 233-mile route from San Diego to Santa Barbara, filling in the missing service with buses. No track damage was immediately found, and service was expected to resume today.

In Los Angeles, the Dodgers took the field against the Houston Astros, and hundreds of Amnesty International members in town for the human rights group’s national meeting continued their work--but moved their sessions outside onto Pershing Square after the Biltmore Hotel suffered superficial damage.

In San Diego, about 1,000 guests were evacuated from the 18-story Hyatt Islandia hotel on Mission Bay after water pipes ruptured. Clad in bathrobes and pajamas, guests milled about in a parking lot for about three hours before they were told they could return to their rooms. Hotel staff served breakfast outdoors.

Sunday’s 7.4 quake was the strongest to strike California since the Tehachapi quake of July 21, 1952, in Kern County. That temblor, a magnitude 7.7, killed 12 people and injured 18. The most powerful earthquake in recorded history in California remains the devastating 1906 earthquake in San Francisco, which seismologists later determined to be a magnitude 8.3

Sunday’s quakes hit on the anniversary of the June 28, 1991, Sierra Madre quake, a magnitude 5.8 shaker that damaged communities east of Los Angeles.

By dusk Sunday, the aftershocks had dwindled. But mountain and desert residents were still on edge, fearing that the worst--the Big One--was still to come. Some planned to sleep in emergency shelters, while others stocked up on supplies.