It’s not the Richter scale: that scale goes bonkers above about magnitude 7. The 9.0 that’s being quoted is actually the moment magnitude (which, by design, corresponds pretty closely to the Richter scale until about magnitude 7, but diverges above).
Saying “Richter scale” is just journalistic sloppiness: assumption rather than investigation. Yes, this is common; but that doesn’t mean I have to let them get away with it. I’m not expecting anything to change as a result, of course.
I decided not to moan about the redundant use of “tsunami waves”:
tsunami: n., pl. tsunamis. A very large ocean wave caused by an underwater earthquake or volcanic eruption.
In other natural disaster news: 1-in-37 chance of asteroid impact on Friday April 13, 2029 that would devastate thousands of square kilometres (based on observations at time of writing).