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Update (3:38 PM EDT):
NBC reports that a 7.3 magnitude earthquake has struck Japan, striking the island of Honshu which is 231 miles east of the Fukushima region. The Japan Meteorological Agency reported a one-foot tsunami and warned a small tsunami could reach the coast at Fukushima.
TEPCO reports that there has been no damage or radiation leak as a result of the earthquake, but their claims could not be verified.
All workers who were near the water at Fukushima Daiichi Nuclear Power Plant have been evacuated to a fortified building on-site - Tepco
— Hiroko Tabuchi (@HirokoTabuchi) October 25, 2013
Update (2:51 PM EDT):
The U.S. Geological Survey is reported a 7.3 magnitude earthquake off the coast off Japan early Friday afternoon.
According to the Weather Channel, Japanese authorities issued a tsunami advisory for Fukushima Prefecture:
Japanese authorities have issued a tsunami advisory for Fukushima Prefecture, expecting a 1-meter (3-foot) tsunami by 1:40pm EDT US time.
— The Weather Channel (@weatherchannel) October 25, 2013
USA Today reports:
The epicenter was located 231 miles east of Japan's Honshu Island. The tremor was felt 300 miles away in Tokyo.
The Japan Meteorological Agency issued a tsunami warning at 1:14 p.m. EST for Fukushima Prefecture.
"Marine threat is in place," the agency warns. "Get out of the water and leave the coast immediately. As the strong current will continue, do not get in the sea or approach coasts until the advisory is cleared."
The warning has been expanded to include Iwate, Miyagi, Ibaraki, and Chiba Prefectures.
The agency said it expects a slight sea level change in coastal regions, but no tsunami damage.
News and updates via Twitter:
The USGS 'tectonic summary' of Friday's quake:
The October 25, 2013 M 7.3 earthquake offshore of Honshu, Japan occurred as the result of normal faulting in the shallow oceanic crust of the Pacific plate. The earthquake occurred outboard (east) of the Japan Trench, which marks the seafloor expression of the subduction zone plate boundary between the Pacific and North America plates, and is immediately up-dip of the source region of the March 2011 M 9.0 Tohoku earthquake. At the latitude of this earthquake, the Pacific plate moves westwards with respect to the North America plate at a rate of 83 mm/yr before subducting beneath the island of Honshu. Note that some authors divide this region into several microplates that together define the relative motions between the larger Pacific, North America and Eurasia plates; these include the Okhotsk and Amur microplates that are respectively part of North America and Eurasia.
The location, depth, and focal mechanism of the October 25 2013 event are consistent with normal faulting rupture near the outer-arc high of the Japan Trench. In this region, normal faulting is encouraged by both the bending of the Pacific plate as it enters the subduction zone, and by stresses transferred from the locked subduction thrust interface to the west. Since the March 2011 Tohoku earthquake, two large events of M 7.7 and M 7.3 have occurred in the vicinity of the October 25, 2013 earthquake. The M 7.7 event, on March 11, 2011, was also a normal faulting event near the outer-arc high and occurred 95 km north of the October 25 event. The M 7.3 event, on December 7, 2012, was a more complex earthquake resulting from thrust motion near the trench 100 km to the northwest of the October 25 earthquake. Since March 2011, 10 additional events, ranging in magnitude from M 6.1-6.4, have occurred in this region east of the Japan Trench.