Just days after the somber one-year anniversary of the March 11 earthquake and tsunami that killed nearly 16,000 people in 2011, Japan was struck by two new earthquakes.
On Wednesday, a 6.8 magnitude quake hit Japan's northern Hokkaido Island. It was followed hours later by a 6.1 magnitude tremor in the Chiba Prefecture, which is directly south of Tokyo and some 600 miles from the location of the earlier quake. Shaking from the Chiba quake was felt as far away as the Japanese capital.
While Wednesday's earthquakes were significantly less severe than the 9.0 magnitude behemoth from last year -- which led to the Fukushima nuclear emergency -- they were nonetheless powerful enough to cause a small tsunami.
The residents of some seaside communities on Hokkaido were ordered to evacuate, but there was no damage reported.
The seismic events of Wednesday were significant, but earthquakes regularly hit Japan and the surrounding waters. Aside from the proximity to the Fukushima anniversary, the tremors were relatively inconsequential.
In fact, in the past seven days, there have been 29 earthquakes in Japan and the surrounding seas, all of them above a magnitude 4.0 (although about eight of them, ranging from magnitudes 4.4 to 6.1, were aftershocks from the Hokkaido quake).
Additionally, the United States Geological Survey claims that 134 earthquakes between the magnitudes 6 and 6.9 occur annually -- a range that includes the recent Japan quake and also a quake in New Guinea -- around the world.
However, scientists at the Tokyo Earthquake Research Institute issued a report in August which stated that the size and severity of last March's earthquake permanently altered the the contact between the tectonic plates under Tokyo, dramatically increasing chances for another major quake hitting the metropolis in the near future.
A change in the pressure of the plates means that focal points on the plate boundaries could shift at the same time. This would create a 7.3-magnitude earthquake, the institute guesses. While this is about 100 times less severe than the one that hit Japan last March, a Tokyo epicenter could do tremendous damage.
We estimate that 10,000 people would die and the economic loss would be around $1 trillion, Naoshi Hirata, a researcher and member of the government's Earthquake Research Committee, told the Daily Telegraph after the report came out.
Even before March , we estimated that there was a 70 percent likelihood of a major earthquake affecting Tokyo at any time within the next 30 years, Hirata added.
That is a very high probability and effectively means that there will be a major disaster here, although we cannot at the moment make a more accurate prediction of when it might strike. All we can say is that individuals, companies, schools and the national and local governments should be prepared.
The effects of the changes in plate tectonics have already been seen in Tokyo, which has experienced thousands of after-shocks in the past year. While minor, the average number of earthquakes in Tokyo tripled in the first six months after Fukushima.
There have also been a number of major earthquakes in the past year and their significance should not to be downplayed --- indeed, people have died following quakes in Indonesia, the Philippines, New Zealand, Pakistan, India and Turkey.
A day after the two Japanese earthquakes on Wednesday, a similar sized quake hit about 2,600 miles to the south, in New Britain, Papua New Guinea. The earthquake was originally listed by USGS as magnitude 6.4, but it was later determined to have had a magnitude of 6.2.
Like Japan, Papua New Guinea sits on the Pacific Rim of Fire, where earthquakes occur with great frequency. About 90 percent of the world's earthquakes occur in this highly active seismic and volcanic zone, including 81 percent of the world's largest earthquakes, according to the USGS.