Comment by sneak

I am using the term in the layperson sense. In that sense, there are generally only 1-3 events per year, affecting fewer than 500 people in a country of 350M. (Most of the gun murders in the US are not from mass shootings.)

Significant earthquakes in Japan occur at least 5-10x more often, and affect 2-4 orders of magnitude more people.

Websites like the one you linked use a definition of the term much different than the one commonly used by everyday people.