A magnitude 7.3 earthquake shook the coast of Japan today, touching off a meter-high tsunami that hit in the same area as the devastating ten-meter waves from the magnitude 9.0 earthquake in March 2011.
The earthquake struck at 6:18 p.m. local time (3:18 a.m. EST), about 250 km east of Sendai, Japan. It happened along the boundary between the Pacific plate and the North America plate — in roughly the same location as the March 2011 quake — due to reverse faulting, as the western edge of the Pacific plate subducts (folds under) the western-most 'limb' of the North America plate. Japan's Earthquake Early Warning system (Kinkyū Jishin Sokuhō), which is one of the best systems in the world, allowed officials to issue a warning shortly before the quake was felt on-shore, affording the population some time to prepare.
The city of Ishinomaki, in Miyagi prefecture — which was one of the regions hit hardest by the tsunami from the March 2011 quake — was one of the areas evacuated as warnings were issued for coastal regions from near Tokyo to the northern tip of Honshu (the largest of the group of islands that makes up the nation of Japan).
"We live less than a kilometre from the water so we went calmly as far back from the water as possible, which is what the advice is if you can't get to higher ground. Everyone evacuated in a calm, orderly way," said Jamie El-Banna, the founder of the disaster relief organization It's Not Just Mud, according to BBC News. El-Banna joined relief efforts in the region in May of 2011, and left a teaching job in Osaka a month later to continue his work there.
There is some speculation, currently, that this earthquake could be another aftershock of the March 2011 quake.
A report on OurAmazingPlanet.com from May 22nd of this year put the total number of aftershocks from that earthquake at 5,229, and geophysicist Jessica Turner — who works for the US Geological Survey (USGS) — told OurAmazingPlanet "It's very normal to have aftershocks more than a year later."
"It's difficult to express how big [the March 2011] earthquake was compared to other earthquakes," said USGS seismologist Paul Earle, according to OurAmazingPlanet. "When you have an earthquake this big, it totally reorients the stress that existed before it, and the Earth responds."
There have been no reports of major damage or injuries as a result of either the earthquake or the tsunami. In the eight hours since the quake, there have been 15 aftershocks recorded, ranging in magnitude from 6.4 down to 4.6.