By Emanuella Grinberg and Ben Westcott, CNN
FUKUSHIMA PREFECTURE, Japan — Aftershocks could continue to shake the Japanese coast for days, the United States Geological Survey said, after a 6.9-magnitude earthquake struck off Honshu early Tuesday morning.
Residents along the east coast of Fukushima Prefecture braced for the worst after the quake set off a tsunami warning along the same stretch of coast devastated by a quake and tsunami in 2011.
Then, a 9.0-magnitude earthquake — one of the worst ever to hit Japan — killed more than 20,000 people and waves of up to 12 meters (40 feet) swamped the Fukushima Daiichi nuclear power plant, triggering a nuclear meltdown.
After Tuesday’s quake, thousands were urged to seek higher ground amid warnings tsunami waves could be up to 3 meters high (10 feet). Three people were injured, police told CNN, while more than 1,900 homes briefly lost power.
The quake struck 37 kilometers (23 miles) east-southeast of Namie at a depth of 11.4 kilometers (7 miles). Eight aftershocks of at least magnitude 5.4 were recorded within five hours of the initial quake.
USGS geophysicist Jessica Turner told CNN the earthquake had been much smaller than the disaster five years ago.
“It is much smaller in magnitude and energy release than the 9.0-magnitude that occurred in March of 2011 … we can expect to see aftershocks for the next several days (but) it’s hard to predict,” she said.
A tsunami advisory, in effect for Japan’s Fukushima and Miyagi Prefectures, was lifted at 12.50 p.m. local time on Tuesday after being put in place earlier in the day.
One of the prime concerns was the crippled Fukushima Daiichi nuclear power plant.
A cooling pump system was temporarily stopped after the quake but soon resumed operation, a spokesman for the Tokyo Electric Power Company Inc. (TEPCO) told CNN. No abnormalities or change in radiation levels were reported.
University of Sydney Disaster Risk Management Expert Dale Dominey-Howes told CNN Tuesday’s earthquake would be devastating for the mental health of survivors still recovering from the 2011 event.
“The simple reality is that the survivors from 2011 haven’t gone back to normal, they’re basically living as displaced people in camps in various locations around central Japan,” he said.
“So today’s earthquake and tsunami basically catapults people back into the moments of the 2011 disaster, all that emotion and pain … Survivors will experience the trauma all over again.”
Small tsunamis reach Japan
Video on social media from Onahama, on the coast of Fukushima Prefecture, featured sounds of sirens in response to the tsunami warning
Images of the port showed waves that the broadcaster described as “backwash” that happens before a tsunami hits shore.
The first tsunami wave reached the coast at Iwaki-shi in Fukushima Prefecture at 6:29 a.m. local time. The largest, a 1.4-meter tsunami, was observed in Sendai, Miyagi Prefecture, at 8:03 a.m. according to Japanese broadcaster NHK.
NHK urged the public to evacuate, cautioning that even if waves appear low in the ocean they can rise as they reach shore. The broadcaster reminded people to dress warmly in the cold rain and urged them to help others leave.
“Please do not think that you are safe. Please evacuate to high grounds,” the network said. “Please think about the worst-case scenario and evacuate right away.”
Earthquake felt in Tokyo
The tremors could be felt as far Tokyo, where American businessman Jonathan Swanson was having breakfast in a hotel and catching up on e-mail.
“Suddenly I felt disoriented,” he told CNN’s Michael Holmes.
Doors started to swing on cabinets and sliding doors started to move. He realized what was happening.
“You could feel the building really swaying back and forth for at least a couple of minutes. It was pretty scary.”
Swanson is from San Francisco and has felt his share of tremors over the years.
“But this was significantly bigger than anything I felt in San Francisco … this was just more extended. The swaying was significantly more than I’d ever felt.”
Japan’s long history of earthquakes
Earthquakes are common in Japan. The most recent was a 6.2 magnitude in late October near Kurayoshi, a city to the west of Osaka, which caused a handful of injuries.
The epicenter of this latest earthquake was not far south of the 2011 quake, which was so severe it moved Japan’s coast 8 feet and shifted the Earth’s axis, ranking among the costliest natural disasters on record.
Speaking to CNN, Geoscience Australia Senior Duty Seismologist Hugh Glanville said while the 2011 earthquake had only been two degrees of magnitude higher than Tuesday’s, a quake’s impact increased logarithmically for every point of magnitude.
“Given the one in 2011 was magnitude 9.0, it was about 1,000 times more powerful than the energy release of this earthquake. For each (degree of) magnitude you go up, it is 32 times the energy of the previous one,” he said.
Glanville said it was possible some aftershocks could be stronger than the original earthquake, possibly about magnitude 7.0.
The devastating 2011 earthquake created huge waves towering as high as 40 meters high.
CNN’s Radina Gigova, Junko Ogura, Joe Sterling and Taylor Ward contributed to this report.