Quake Rocks Japan, Kills 686 : A 7.2 Temblor Devastates Kobe, Trapping 500 : Disaster: More than 2,100 buildings are destroyed or severely damaged in western part of nation. Trains derail, expressways buckle, fires erupt after pre-dawn jolt.

A powerful earthquake rocked western Japan before dawn today, killing nearly 700 people and trapping more than 500 others as buildings collapsed, trains derailed, elevated railways and expressways buckled and fires erupted in the major port city of Kobe.

The quake, which shook buildings 40 miles away in Kyoto, was measured as magnitude 7.2 at its epicenter, on Awaji Island about 20 miles from Kobe, a city of 1.5 million 270 miles west of Tokyo.

It struck at 5:46 a.m.--an eerie coincidence for Southern Californians marking the first anniversary today of the 6.7-magnitude Northridge quake, which also occurred near daybreak.

National police reported 686 dead, 534 missing and 2,439 injured. More than 2,100 buildings were reported destroyed or severely damaged.

As reports of extensive damage continued to pour in, fires were still burning in at least seven sections of Kobe more than nine hours after the earthquake struck. Black clouds of smoke rose above the city as if it had suffered a bombing. Water mains were ruptured, hampering efforts to battle the fires, and blackouts left nearly 1 million people without electricity.

Most of the fatalities were reported in and around Kobe.

Police in the neighboring city of Ashiya reported that 69 buildings there had collapsed. NHK, the semi-governmental TV network, said up to 200 people were believed buried in rubble there.

A dozen Buddhist statues designated as national treasures in the famed Sanjusan Gendo Temple in Kyoto were reported damaged.

Television showed dozens of families taking refuge from their ruined homes on mattresses spread out on streets and sidewalks. Entire blocks of buildings were reduced to rubble.

The first floor of a hotel in Kobe collapsed, and TV cameras showed guests being helped out of second-floor windows.

On one expressway where part of the elevated pavement had fallen to the ground, TV cameras showed a bus dangling perilously from the broken end of the highway. There was no sign of passengers inside the bus.

A truck was shown sandwiched between two collapsed sections of an expressway, but it was unclear whether it was the same freeway. At another point, concrete and steel pylons had cracked at their base and toppled over so that the edge of the pavement they had supported rested on the ground for more than half a mile. At least two people died when more than 50 cars slid off the toppled expressway.

Although information about derailed commuter trains remained scanty, they apparently had been running without passengers, en route to their first scheduled runs of the morning.

Mass transit facilities throughout Japan normally stop operating from around 12:30 a.m. until shortly after 5 a.m. If the earthquake had struck two to three hours later during the morning rush hour, there would have been even more casualties from damaged expressways and railways, commentators noted.

Prime Minister Tomiichi Murayama called an emergency meeting of his Cabinet and set up a national headquarters to deal with recovery efforts that are expected to continue for months. Units of the Self-Defense Forces, the Japanese military, were dispatched to Kobe.

Trading on the Osaka Stock Exchange was suspended in the afternoon.

Prof. Suminao Murakami, an earthquake expert at Yokohama National University, said the widespread damage to both elevated railways and expressways destroyed a “myth” that officials of Japan’s Public Highways Corp. had perpetrated in the aftermath of the Northridge earthquake. They said that Japanese expressways had been constructed far more solidly than those in Los Angeles, he noted.

“The quake showed that expressways anywhere in Japan could suffer the same kind of damage,” he said.

Trains were reported derailed at seven locations.

Helicopter TV cameras showed at least three commuter railway cars overturned at one station. Fires were sweeping through shops adjacent to the station.

Rail travel was halted throughout the area, and authorities closed all expressways. NHK television footage showed twisted expressways, collapsed sections of highway and an entire elevated railway yard that had folded down to the ground in the middle.

NHK showed film of its Kobe office being shaken violently by the quake, which toppled filing cabinets and moved desks several feet.

A resident of Nishinomiya, a city near Kobe, told Reuters news agency she was shaken awake in her third-floor apartment. “There was a big shaking. I felt like I was being thrown into a deep pit like hell. It was so big. It was a terrible shaking,” she said.

Telephones were reported operating, although lines reserved for emergency calls to police and the fire department were swamped with calls, making communications difficult or impossible.

By noon, food shops were reported sold out of supplies of bread and box lunches.

Itami Airport in nearby Osaka continued to operate, but flights were reported delayed at the new multibillion-dollar Kansai Airport on an artificial island in Osaka Bay off Kobe. Trains on the Bullet Line were running only between Tokyo and Nagoya, at one end, and between Hiroshima and Fukuoka, at the other end of the line, with no service available to Kyoto, Osaka and Kobe.

Meanwhile, the White House said Monday that the United States will “stand ready to help” Japan recover from the devastating earthquake.

President Clinton, in Los Angeles to commemorate the one-year anniversary of the Northridge earthquake, called Ambassador Walter F. Mondale in Tokyo and instructed him to keep abreast of the situation.

White House Press Secretary Mike McCurry said the Federal Emergency Management Administration is prepared to offer technical expertise or emergency response if requested by the Japanese.

“Obviously, if there is a way the U.S. government can assist, we stand ready to help,” he said.

Clinton was “greatly concerned” about the loss of life in Japan and offered his condolences, according to McCurry.

He said there are 10,000 to 20,000 Americans who live in the area struck by the quake. There were no reports of American casualties, McCurry said.

Today’s earthquake, NHK said, was the biggest to strike an urban area in Japan since a 6.1-magnitude quake severely damaged the city of Fukui in 1948. And it was the fifth major temblor in the magnitude 7 range to shake parts of Japan since Oct. 4. But unlike the others, which were out to sea off northern Japan, this one was centered very close to a highly urbanized area.

That proximity to populated areas, plus the quake’s comparatively shallow depth of 12 miles as estimated in first reports, caused damage and casualties that quickly exceeded those of earlier quakes.

As in the weaker Northridge quake, the Japanese temblor could be a major demonstration of how steel frame and other high-rise buildings fare under heavy shaking, U.S. scientists said.

Hiroo Kanamori, director of the Caltech Seismological Laboratory, who was born and educated partly in Japan, noted that the area west of Osaka and near Kobe where today’s quake struck had not suffered many quakes in the past.

While Japanese authorities put the preliminary magnitude at 7.2, several times stronger than the Northridge quake, U.S. scientists at the National Earthquake Information Center in Golden, Colo., said their preliminary assessment assigned it a magnitude of 6.9, about twice as powerful. It is common for preliminary estimates to differ.

Kanamori said in an interview that today’s quake occurred 130 miles from one tectonic plate boundary, known as the Nankai Trough, and 30 miles from a second plate boundary, in an area that had not been the focus of any Japanese earthquake prediction experiments.

“This is not really a large event by Japanese standards,” he said, “but since it is near a highly populated area, like Northridge, it’s done quite a bit of damage.”

Japanese scientists have long expressed concern about a major quake on the Nankai Trough, just as California scientists have long pointed to the San Andreas fault as the eventual site of great quakes.

But, as in both the Northridge quake and the 1971 Sylmar quake, the first sizable temblor to strike in the vicinity came at an unexpected location, well away from the famous geological faults.

Only nine days ago, three major tremors struck Japan. They ranged in magnitude from 5.2 just outside Tokyo to 6.9 and 4.2 in Hachinohe, 325 miles north of the capital.

Earthquakes with a magnitude of more than 7 struck rural areas of northern Japan three times in 1993. Except for a tsunami that killed more than 200 people on one island, damage from those tremors was minor.

Times staff writer Kenneth Reich in Los Angeles contributed to this report.

* A CULTURAL PROFILE: Quake-hit Osaka reflects the soul of Japan. World Report.