|The Pacific and Philippine Sea plates have slid under the Eurasian and North American plates that support Japan. On balance, the upwardly displaced plates will get most of the earthquake action. Various reports have stated that the Sendai quake alone shifted Japan's coastline as much as 8 entire feet.|
The amount of earthquakes in Japan have picked up to almost ridiculous frequency lately, and this behavior goes beyond what geologists would attribute to normal aftershock activity. There is a fundamental change afoot within the earth's crust, as an article from the The Daily Yomiuri Online points out:
The phenomena can be attributed to the enormous changes in the force exerted in the Earth's surface in the eastern part of the nation due to the Great East Japan Earthquake, which measured magnitude-9.0 on the open-ended Richter scale, according to seismologists.
On Tuesday, a magnitude-5.6 earthquake occurred in northern Nagano Prefecture, while on the same day a magnitude-6.4 earthquake struck offshore from eastern Chiba Prefecture. On Monday, a magnitude-7.0 earthquake took place in eastern Fukushima Prefecture.
The Metrological Agency warned, "Earthquakes have come to occur frequently as the geological dynamics of eastern Japan have changed due to the March 11 earthquake."
"We have to expect more earthquakes in the magnitude-7.0 class for the time being," it warned.
"An earthquake could hit the Tokyo metropolitan area with its focus directly below the city. We'll have to observe the situation carefully," Yamaoka added.
The professor anticipates the rise in seismic activity in eastern Japan will continue for four or five years. He said magnitude-7 quakes "are likely to occur once or twice in the next month."