A powerful earthquake rocked Japan's picturesque northern coastline today, spawning 15-foot tidal waves, leaving at least 41 persons dead and causing widespread damage over seven of the country's prefectures.

The quake, the most deadly to hit Japan in 15 years, hit shortly after noon with its epicenter in the Sea of Japan about 100 miles off the shore of Akita prefecture in the country's northeastern Tohoku region and 340 miles north of Tokyo. The quake registered a magnitude of 7.7 on the open-ended Richter scale, and left 60 persons injured and 61 others missing.

As aftershocks from the tremor continued to rattle the area late into the night, Japanese television crews provided detailed coverage of the disaster, reflecting the high level of public interest in this earthquake-conscious country.

Among the most vivid scenes recorded live by television cameras were those of the actual quake itself. In Akita city, people were shown fleeing from their homes as pavement buckled and broke. Others were seen by viewers throughout the nation squatting on streets in an attempt to shelter themselves alongside parked cars from falling debris.

The heaviest toll, however, came as a result of a violent series of tidal waves, the first of which slammed into the coastline only minutes after the quake and before local government authorities had time to issue an alert.

In the most tragic incident, 49 elementary school children and their teachers on a seaside outing were swept away by the high waves. Two of the children's bodies were later recovered, and 11 others were missing and presumed dead.

The pupils, all of them fourth and fifth graders, were having lunch on the tip of the scenic Oga Peninsula near Akita when the quake struck.

Reports from the scene said a huge tidal wave swooped down on the children and washed them away in a matter of seconds. Some of the children were crying for help and shouting "mommy, mommy" while clinging to logs, reports said.

A Swiss woman on a sightseeing tour of the same area also died when the tidal wave hit, police said. Unofficially identified as Magdalena Brandenberger, 38, from Zurich, she was found dead after failing to reach the safety of a rock as waves approached, an official at a nearby aquarium said.

In Akita city, the force of the quake toppled concrete walls, cracked a highway and collapsed the fourth-floor ceiling of a six-story department store, killing one shopper, injuring four others and showering hundreds with plaster.

At a landfill project about 37 miles north of Akita city, six workers were killed when the towering waves smashed into a breakwater that they were building. Vessels of Japan's Maritime Safety Agency dispatched to look for another 39 missing workers were forced to call off the search because of darkness.

The quake also sparked a rash of fires, including one at an oil refinery and a thermal power plant in Akita, and others in Hirosaki city north of Akita, according to the Japan Broadcasting Corp.

Japanese television crews operating out of helicopters captured bizarre scenes of automobiles floating out to sea and fishing boats that had been deposited in farmers' fields by the high waves.

Estimates of the financial toll from the earthquake and tidal waves were not immediately available. But Japan's National Police Agency estimated that more than 400 homes in the area had been destroyed along with 375 vessels, mostly belonging to local fishermen.

The quake brought a temporary halt to Shinkansen bullet train service to the Tohoku area and partially isolated the remote region from the rest of Japan as roads, bridges and telephone links were cut.

The government declared a state of emergency and put together a task force of 19 ministries and agencies to assist the stricken area.

Today, Japan is jolted by more than a thousand tremors a year large enough to be felt by its inhabitants, many of them in large cities like Tokyo. The Japanese government has spent millions of dollars in recent years on a nationwide program designed to prepare big urban centers for major earthquakes, which officials are sure will come.

Today's toll was the worst in a Japanese quake since 1968, when a quake measuring 7.9 on the Richter scale killed 52 people and injured 330 people in the same area.

A 7 on the Richter scale, which measures ground motion as recorded on seismographs, is considered a major earthquake, capable of heavy and widespread damage.