Japan's Meteorological Agency reports that they could recall "no other case" resembling the recent earthquake situation in Kyushu:
Editorial: Quake-prone Japan must remain on guard against nuclear accidents
April 28, 2016 (Mainichi Japan) http://mainichi.jp/english/articles/20160428/p2a/00m/0na/019000c
[excerpted] Responding to the latest quakes, the Japan Meteorological Agency and experts repeatedly expressed their views that that was no precedent of a magnitude-6.5 level inland quake being followed by an even bigger quake, and that they could think of no other cases wherein seismic activity had occurred in three separate locations at the same time. The government's Earthquake Research Committee also expressed the view that the Futagawa fault was longer than originally thought.
However, although the situation is unprecedented, Kyushu Electric "assures" the public that the Sendai nuclear power plant is "safe":
Kyushu Electric assures public that nuclear plant is safeTHE ASAHI SHIMBUN April 29, 2016 http://www.asahi.com/ajw/articles/AJ201604290059.htmlBlack swan events are (regarded as) improbable, high consequence events. Although they are regarded as improbable, calculations of risk are too often systematically biased by limited reference frames and other cognitive biases that distort understanding of patterns:
Kyushu Electric Power Co. brushed aside safety concerns expressed in thousands of phone calls and e-mails, saying its Sendai nuclear plant in Kagoshima Prefecture faces no danger from the quakes rattling the southern main island.
The Nuclear Regulation Authority also supports the utility’s stance that there is no need to shut down the nuclear plant, even as a safety precaution during the seismic activity.
Yesterday, The Asahi Shimbun reported that over 1,000 earthquakes had been recorded as occurring in Kyushu between April 14 and April 28:
Number of earthquakes exceeds 1,000 in Kumamoto area. THE ASAHI SHIMBUN. April 28, 2016 http://www.asahi.com/ajw/articles/AJ201604280024.htmlThe earthquake situation in Kyushu is evolving into a black swan event. The prospect of another nuclear catastrophe in Japan cannot be ruled out in this context given the uncertainties produced by the series of anomalous events. A precautionary approach should be adopted but nuclearity is a mania that, akin to Midas' curse, blinds decision-makers to potentially catastrophic consequences.