You may note the tsunami stones, marking flood levels from the 1930s with inscriptions like, "Do not build any homes below this point (…) Remember the calamity of the great tsunamis." Also, earthquakes, even sever ones (compare Kobe), are expected and reoccurring events in Japan. They had been explicit design criteria for the power plant. This was quite literally a 100-year event with similar past events happening in the last 100 years before this. So this is hardly a black swan.