Aftershock

A month to the day after the 9.0 magnitude earthquake first struck Japan, one of the most powerful aftershocks hit Japan with a magnitude of 7.1. 

Aftershocks are caused when the crust around the fault settles after it has been forced to move as a result of the main earthquake. Aftershocks, although not as powerful as the earthquake can be extremely deadly and are unpredictable. 

Many times, the aftershocks occur shortly after the main quake, although they can take a month or more to develop. 

In the 72 hours immediately following the quake, there were a total of 225 aftershocks greater than magnitude 4.5, the largest of which was 7.1. To date, that number has climbed to near a thousand and is expected to increase. 

Aftershocks are of some concern, especially the most recent which caused another disturbance in the power supply at the Fukushima nuclear plant. This was the same problem experienced by the plant that caused it to enter the nuclear struggle it currently has. 

Another danger of aftershocks is the risk they pose to buildings already damaged by the previous quakes. After the initial quake, many of the buildings that remain standing are weakened substantially. 

Another quake can be enough to cause the building to topple and fall to the ground, delaying rescue efforts along with building repairs. 

Scientists continue to count the number and magnitudes of the aftershocks and study their effects on the already destabilized communities. 

Unfortunately, their severity or times are unknown so workers are forced to wait helplessly until the quake stops before resuming recovery efforts.

The tremors will likely continue and more are expected in the coming weeks.