From Fukushima Diary
Unidentified explosive sound heard in Iwaki city twice on 8th Feb
Iwaki city citizens reported to police, fire department and city hall that they heard something explode on 2/8/2016.
It reportedly sounded like thunder or exploding meteorite. It also shook the buildings and windows.
The most reports were sent from Onahama area. The cause hasn’t been identified nor any damage was reported.
Onahama area is approx. 60km from Fukushima plant. Tepco has not announced anything about the plant status related to this issue.
Video and sound can be watched here.
Possible explosion in Iwaki city still unidentified
February 19, 2016
The cause of the possible explosion still have not been identified.
NIED (National Research Institute for Earth Science and Disaster Prevention) observed weak tremor that last for a few tens of seconds around 15:30 of 2/8/2016, when the explosive sound was observed in Iwaki city. The tremor was measured even in Hitachi city of Ibaraki prefecture. However NIED denies the possibility of an earthquake because the tremor was observed in widespread area at once. They also denied the possibility of meteorite.
Meteorite was not seen by anyone either.
Ministry of defense comments none of their fighter aircraft flew above Iwaki city that time.
However, none of the investigation has been implemented for the potential connection with Fukushima plant so far.