SAN FRANCISCO (CBS SF / AP) -- A cluster of earthquakes around the world hit just before the third anniversary of the devastating 9.0 Kobe earthquake that set off a Pacific-wide tsunami causing widespread destruction from Japan to California, and triggered a nuclear meltdown in 2011.
The first quake, a 6.8 off the Eureka coast on Sunday night caused little to no damage, but shook homes and rattled nerves around Northern California. Dozens of aftershocks, some approaching a magnitude 5 continue to move the San Andreas fault.
Another quake, initially a 6.8 magnitude as well, but later downgraded to a 6.4 hit Monday near the Sandwich Islands in the southern Atlantic.
A 5.9 magnitude earthquake hit Monday north of Papua, New Guinea along the Pacific "Ring of Fire."
Even Japan was shaken by a mild 4.8 earthquake Monday, as the nation pauses Tuesday to honor those who died in the Kobe quake.
Prime Minister Shinzo Abe pledged to boost rebuilding efforts as the country marked the third anniversary of the devastating March 11th, 2011 earthquake and tsunami that left nearly 19,000 people dead, destroyed coastal communities and triggered a nuclear crisis.
Japan has struggled to rebuild towns and villages and to clean up radiation from the meltdowns at the Fukushima Dai-ichi nuclear power plant. Reconstruction plans are finally taking shape, but shortages of skilled workers and materials are delaying the work.
The triple disasters known in Japan as 3-11 killed 15,884 people and left 2,636 unaccounted for on its northeastern coast. The country has earmarked 25 trillion yen ($250 billion) for reconstruction through March 2016.
Three years later, nearly 270,000 people remain displaced from their homes, including many from Fukushima prefecture who may never be able to return home due to radioactive contamination.
During a ceremony in Tokyo, officials and representatives of the survivors offered a minute of silence to mark the moment, at 2:46 p.m., when the magnitude 9.0 earthquake struck off the Tohoku coast. It was the strongest quake recorded in Japan's history.
Abe has visited disaster-hit areas regularly since taking office in late 2012, and said Tuesday he has seen signs of progress. Farming and fishing resumed in some areas, and some people have moved to public housing from shelters, he said, promising to do more.
"We must further speed up the reconstruction so that everyone affected by the disasters can return to ordinary life as soon as possible," Abe, wearing a dark formal suit, said during the solemn ceremony.
Abe has promised to move hundreds of communities along that ravaged coast to higher ground to avoid future tsunamis, and build thousands more public housing units within a year in Iwate and Miyagi prefectures.
In Fukushima, reconstruction has lagged further behind in some areas because of the nuclear disaster.
Several towns are still off-limits due to high radiation.
The plant has stabilized substantially, but is still plagued by frequent leaks of radioactive water and other mishaps, triggering concern about whether it's really under control. The leaks are hampering the plant's decommissioning, which is expected to take about 40 years.
Yukari Tanaka, a resident of Futaba town, where the Fukushima Dai-ichi plant is located, told the ceremony she couldn't look for her father after the tsunami because they were ordered to evacuate. Weeks later, her father was found dead under the roof of their tsunami-toppled house.
"I never forget how I regretted that I had to evacuate, leaving my father behind," Tanaka said.
Emperor Akihito, who also attended the ceremony, said that his heart breaks when he thinks of the Fukushima residents who have no idea if they can ever return home.
"Many disaster survivors are still experiencing difficulties. It is important that all people of Japan unite their hearts and stand by each other for a long period so that they can live without losing their hopes and in good health," Akihito said.
In northern Japan, some tsunami survivors held their own memorial events for their loved ones earlier Tuesday.
In the once-bustling fishing town of Minamisanriku, local residents gathered in front of the frame of what used to be the town's disaster prevention center, where dozens of town employees died in the tsunami. The residents prayed in front of a small table filled with flowers, a Buddha statue and incense.
Much of the town's coastal area remains deserted, except for a few structures that survived.
Katsuo Izumi, who lost his wife in the tsunami, said his disaster-hit town of Higashi-Matsushima has seen some rebuilding of public housing, schools and other facilities. Altogether, the city lost 1,000 residents.
"We survivors have a responsibility to live a full life on behalf of those who perished in the tsunami," he said at a Tokyo ceremony, representing the survivors from Iwate prefecture. "I hope to see the reconstruction achieved as soon as possible."
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