Here's something that was posted to this page a few minutes ago by Paul Beaufait:

--- start quote ---
Facebook searches I've tried have failed to turn up anything like this, so I'd like to share a pointer to a site where you can sign-up for email disaster alerts in Japanese for Kumamoto City:
https://www2.fastalarm.jp/kumamoto/htdocs/ (熊本市災害情報メール)
Once you submit an email address (via the topmost link), and follow the link in a follow-up message that you'll receive, you'll need to make selections from a variety of menu options: some quite fine-grained (e.g.: earthquakes filtered by intensity and location), and others not-so (e.g.: volcanic eruptions throughout the archipelago).
One morning last week, for example, I received an air-quality alert for high concentrations of fine particulate matter (< 2.5 µ), and another as soon as the concentrations diminished.
--- end quote ---

Thanks Paul! This is a good service. I think it shouldn't be too terribly difficult for the city to make versions of it in other languages (the phrases needed could be pre-programmed so that the messages could be generated more-or-less automatically) but for now we only have Japanese.

https://www.facebook.com/Kumamotoi/posts/467992026683385