A 7.1 magnitude earthquake – considered a serious and large earthquake, but not so large as the 9.0 magnitude quake that struck Japan in March 2011 – struck off the east coast of Honshu, Japan on July 10, 2011. The quake took place 411 kilometers (255 miles) northeast of Tokyo.
Tokyo Breaking News reports that tsunami advisories were issued. Officials said they expected a tsunami of less than one meter in some areas. [UPDATE 10:15 p.m. CDT July 9 (3:15 UTC July 10) The Japan Meteorological Society has cancelled all tsunami warnings related to this earthquake.]
There have been no immediate reports of injuries or damages.
According to Reuters and the Huffington Post, Fukushima nuclear plant workers evacuated to higher ground following the earthquake. Tokyo Electric Power reportedly said that there did not appear to be any immediate further damage at the nuclear plant.
According to the US Geological Survey, the quake hit at 00:57:12 Universal Time (UTC) on July 10, 2011.
The Associated Press reported:
The quake hit at 9:57 local time (0057 GMT) and a warning of a possible tsunami was issued for most of the northeastern coastline. The epicenter of the quake was in the Pacific Ocean off the coast of Japan’s main island, Honshu.
A 7.1 magnitude earthquake is considered a serious earthquake. There are approximately 20 earthquakes from 7.0 to 7.9 somewhere in the world each year, in contrast to 100 earthquakes per year of magnitude 6.1 to 6.9 and 500 earthquakes per year of magnitude 5.5 to 6.0 (see table from UPSeis from Michigan Tech). The Richter magnitude scale for earthquakes is designed such that – for each whole number you go up on the Richter scale – the amplitude of the ground motion recorded by a seismograph goes up ten times. In other words, a magnitude 8.0 earthquake would result in 10 times the amount of ground shaking as a magnitude 7.0 earthquake, and the 9.0 magnitude earthquakes on March 11, 2011 in Japan would be 10 times stronger than an 8.0.
Bottom line: a 7.1 magnitude earthquake struck off the eastern coast of Japan at 00:57:12 Universal Time (UTC) on July 10, 2011. Tsunami advisories were issued and later cancelled. There have been no immediate reports of injuries or damages. Fukushima nuclear plant workers were evacuated to higher ground.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.