Earthquakes Hit Japan, Cuba, California: Cause for Concern?

A 6.2-magnitude earthquake rattled Japan's northeastern coast on Thursday.

Japan's Meteorological Agency said there was no risk of a tsunami, and so far there have not been any reports of injuries or damages.

The quake hit off the coast of Honshu, Japan's largest island. The epicenter was about 140 miles east of Toyko and six miles beneath the sea floor.

Cuba was hit by a 6.0 earthquake on Thursday as well, according to the U.S. Geological Survey. The quake happened before 5 a.m. local time off the island nation's southern coast.

Additionally, minor quakes shook Birmingham, Alabama and southern Califiornia.

Are multiple earthquakes in the same day anything to worry about?

Considering that there are about 1.5 million earthquakes a year, not really. And that's just above magnitude 2.0. Below that, there are more millions.

Additionally, USGS claims that 134 earthquakes between the magnitudes 6 and 6.9 occur annually, the same magnitude as those that hit Cuba and Japan. Statistically, is it not unlikely that two would happened on the same day.

In the past week, there have been 300 earthquakes in Alaska alone, 13 of which happened Thursday. In California and Nevada, there were nearly 400 quakes over the same period, the largest reaching around 4.0 magnitudes, according to USGS.

Yet, 2011 has seen its share of large-scale quakes. In March, a 9.0 earthquake hit Japan, causing enormous damage and a nuclear disaster at the Fukushima power plant. A month earthlier, a 6.3 magnitude earthquake in Christchurch, New Zealand killed nearly 200.

On Sept. 6, a 6.6 magnitude earthquake hit the Indonesian island of Sumatra, killing a 12-year-old boy who was lying in bed and a man who died of a heart attack as he fled his home.

And while earthquakes are common in Japan, scientists at the Tokyo Earthquake Research Institute reported last month that the 9.0-magnitude earthquake that rocked Japan in March changed the contact between the tectonic plates under the capital city, drastically increasing the chance that a quake could hit Tokyo 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 in 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.

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, he said.

All we can say is that individuals, companies, schools and the national and local governments should be prepared.

Hirata told the British daily that Tokyo has already seen the effects of the changes in plate tectonics. Tokyo generally has two minor quakes a month, but since March, that number has jumped to an average of six per month. This rise is true for most of Japan, which has experienced a total of about 500 earthquakes since the Fukushima disaster that killed almost 20,000 people.