There have been many aftershocks and a few other, quite strong earthquakes in Japan, following the massive earthquake on 11 March 2011.
There were a few strong quakes in the region covering mid-Niigata and northern Nagano until a couple of days ago, which damaged properties and forced people to evacuate. The epicentre of the quake on 12 March 2011 at 03:59 is marked by a green balloon on the map. People would soon be able to return to their homes, after the inspectors judge the houses to be structurally sound. Seismologists were not sure, whether these were completely different, unrelated earthquakes from the one that hit the north east or not. It seems that while a direct causal link cannot be established, the geological conditions may have changed as a result of the massive earthquake in the north east, and made earthquakes likelier in this area. In other words, the existing conditions were exacerbated.
As if to make the picture even more complicated and worrisome, there was another strong quake at 22:31, 15 March 2011, in eastern Shizuoka, marked by the blue balloon, which is another quake-prone area. Like the quake in the Nagano / Niigata area, it’s unclear whether there were direct links between this quake and the one in the north east. The epicentre was near an area where a magnitude 8-plus quake (Tōkai earthquake) has been long considered a distinctive possibility, because of the plate movement, and periodic quakes in the past. However, the experts at Japan Meteorological Agency, and those quoted by the media, agree that this quake is unrelated to a potential Tōkai earthquake, since the location and mechanism of the quake did not fit the criteria.
It’s probably true to say that human beings tried to link events, even if they are not related, to make sense of what is happening to them. Some people are understandably apprehensive about what is going to happen.