Today, William introduced us to a Kumanichi article about a possible man-made cause of the landslide that took out the Aso Ohashi:
https://www.facebook.com/Kumamotoi/posts/1037456022994496
I saw a report on NHK today about this as well. Huge quantities of water from facilities operated by Kyushu Electric may have played a role in two landslides:
http://www3.nhk.or.jp/news/html/20160513/k10010519991000.html
The landslide of the other side of the Aso Ohashi killed two people.
None of the articles I read about this mention the possibility that one of the earlier quakes might have caused a leak that, by moistening the soil of the slope, would have made it more susceptible to a landslide when the 7.3 magnitude quake hit. The third image I’m posting shows that the Minami Aso area experienced 5 lower shaking during the quake that hit on the 14th and it’s possible that that caused some leaking. Of course, this in only speculation on my part but water, steep slopes, and earthquakes are a dangerous combination so the possible influence of such a leak is something that definitely needs to be looked in to.
Finally, the first two images you see are from a video news report that can be found here:
http://news.tv-asahi.co.jp/news_society/articles/000074703.html
– Kirk