A second earthquake—magnitude 7.4—has hit northeastern Japan, prompting a tsunami warning. The quake, strong enough to move buildings in Tokyo, hit 78 miles north of the devastated Fukushima plant at 11:32 pm, local time.
Update 1: TEPCO officials say they've not encountered any further problems with Fukushima's six reactors in the aftermath of this newest quake, although the area has been hit by electrical blackouts.
Update 2: Residents of the Miyagi Prefecture have been told to move to higher ground immediately in advance of an expected tsunami.
Update 3: Authorities at Miyagi's Onagawa nuclear plant say no elevated radiation levels have been detected around the facility, the reactors of which were shut down after the original March 11th quake.
Update 4: Electrical blackouts are being reported in the vicinity of the quake's epicenter as well.
Update 5: A Japanese government spokesperson says tsunami waves are expected to have already hit land, although none have been observed.
Update 6: Six injuries have been reported so far by local fire departments.
Update 7: Water injection at the Fukushima plant has continued despite the latest tremor.
Update 8: The USGS has pegged the quake's magnitude at 7.1, rather than 7.4.
Update 9: Good news: all tsunami alerts have been canceled, although residents are still being advised to stay away from the coast in case of shifting tides.
Update 10: The local intensity of the quake has been measured at 6+ on Japan's own tremor scale of 1 - 7.
Update 11: Two of the three power lines used to cool the Onagawa nuclear plant's deactivated reactors are offline, although again, no radioactive abnormalities have been observed.
Update 12: The AP, quoting USGS geologist Paul Caruso, reports this newest tremor hit at almost the exact same coordinates as the original March 11th earthquake.
Update 13: A Japanese Meteorological Agency rep says further strong aftershocks are still possible in the immediate future.
Update 14: The quake is being categorized as an aftershock from the March 11th event—by far the strongest to date.
Update 15: MSNBC's live feed has concluded, but we're continuing to monitor the situation and will update as warranted.
Update 16: Kyodo News has put the death toll from yesterday's quake at four.
Check our Definitive Japan Crisis Timeline for more information as it happens.