|USGS earthquake location map.|
February 16, 2015 - JAPAN - An earthquake measuring at 6.8 magnitude has struck off Honshu island in northern Japan, the US Geological Survey (USGS)said.
There are local media reports that a tsunami warning has been issued for Iwate Prefecture, although the Pacific Tsunami Warning Center declares that there is no tsunami threat from the tremor.
|USGS earthquake shakemap intensity map.|
Japan Meteorological Survey has issued a tsunami advisory for the Iwate Prefecture, warning that the waves may reach 1m in height.
Meanwhile, an evacuation order has been issued for coastal towns in Iwate prefecture. Thousands of people are reportedly leaving their homes while boats are sailing out of the harbor. People in some coastal areas have been advised to leave their homes due to anticipated waves of up to 1m in height.
Small tsunamis of some 10 centimeters have now reached the shore some 45 minutes after the initial reports, with people being advised to stay away from the coastal area. There were no immediate indications of damage or injuries.
“We are using the emergency broadcast to advise people to keep away from the sea ... the quake was pretty strong and lasted a long time so I thought there would be a tsunami warning," Kozo Hirano, an Otsuchi Town official in Iwate, told NHK.
#Japan NHK TV showing live pictures of coastline at #Tsunami risk. Loudhailers asking residents to evacuate. pic.twitter.com/sz94hVmOws
— Mark Stone (@Stone_SkyNews) February 16, 2015
This is the second major earthquake to strike the planet today. Earlier a 6.7 magnitude earthquake struck northwest of Visokoi Island, in the South Georgia and the South Sandwich Islands region. That temblor has since been downgraded to a magnitude of 6.2 by the USGS.
The quake that struck Japan was recorded at around 8 am local time at a depth of approximately 10 kilometers and was located at 39.848°N 142.813°E. The epicenter was located off the Sanriku Coast, extending from southern Aomori prefecture, through Iwate prefecture and northern Miyagi prefecture.
There are no initial reports of any shaking or damage to Fukushima where the crippled nuclear power plants are located.
|USGS historical seismicity for the region.|
A spokesman for Tokyo Electric Power, which owns the nuclear plants, said no irregularities have been found as yet at its Fukushkma Daiichi or Daini plants.
There were no irregularities reported at the Onagawa and Higashidori nuclear plants in nearby Miyagi and Aomori prefectures, the facilities’ operator Tohoku Electric Power Co. said.
Japan lies along the western edge of the Pacific Ring of Fire, and is one of the most tectonically active places on Earth. The Ring of Fire is a narrow zone around the Pacific Ocean where a large chunk of Earth's earthquakes and volcanic eruptions occur.
About 1,500 earthquakes strike the island nation every year. Minor tremors occur on a nearly daily basis. Deadly quakes are a tragic part of the nation's past.
On March 11, 2011, Japan was struck by the shockwaves of a 9.0 magnitude undersea earthquake originating less than 50 miles off its eastern coastline. The most powerful earthquake to have hit Japan in recorded history, it produced a devastating tsunami with waves reaching heights of over 130 feet that in turn caused an unprecedented multireactor meltdown at Fukushima Daiichi Nuclear Power Plant. This triple catastrophe claimed almost 20,000 lives, destroyed whole towns, and will ultimately cost hundreds of billions of dollars for reconstruction.
Today's earthquake struck in the same region hit by the devastating 9.0 quake. Japan is still battling the consequences of the three meltdowns and struggling with the clean-up of the nuclear catastrophe aftermath.
Tectonic Summary - Seismotectonics of Japan and VicinityJapan and the surrounding islands straddle four major tectonic plates: Pacific plate; North America plate; Eurasia plate; and Philippine Sea plate. The Pacific plate is subducted into the mantle, beneath Hokkaido and northern Honshu, along the eastern margin of the Okhotsk microplate, a proposed subdivision of the North America plate. Farther south, the Pacific plate is subducted beneath volcanic islands along the eastern margin of the Philippine Sea plate. This 2,200 km-long zone of subduction of the Pacific plate is responsible for the creation of the deep offshore Ogasawara and Japan trenches as well as parallel chains of islands and volcanoes, typical of Circumpacific island arcs. Similarly, the Philippine Sea plate is itself subducting under the Eurasia plate along a zone, extending from Taiwan to southern Honshu that comprises the Ryukyu Islands and the Nansei-Shoto trench.
|USGS plate tectonics for the region.|
Subduction zones at the Japanese island arcs are geologically complex and produce numerous earthquakes from multiple sources. Deformation of the overriding plates generates shallow crustal earthquakes, whereas slip at the interface of the plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. At greater depths, Japanese arc earthquakes occur within the subducting Pacific and Philippine Sea plates and can reach depths of nearly 700 km. Since 1900, three great earthquakes occurred off Japan and three north of Hokkaido. They are the M8.4 1933 Sanriku-oki earthquake, the M8.3 2003 Tokachi-oki earthquake, the M9.0 2011 Tohoku earthquake, the M8.4 1958 Etorofu earthquake, the M8.5 1963 Kuril earthquake, and the M8.3 1994 Shikotan earthquake.
- RT | USGS.