Yep, impressive structures. Living where they do - in earthquake-prone part of the world - the Japanese have to prepare as best they can for earthquakes, tsunami, typhoons. Bear in mind that these huge underground temporary water retention tanks also have to hold up to earthquakes. & I assume they have independent power generation equipment too, & probably some housing for workers to live on-site during an emergency.
It's admirable planning. With just a little work, those same structures could shield people against nuke fallout, most conventional weapons, bomb strikes.