The West Coast of the United States is a beautiful place that has seen its fair share of earthquakes. In fact, the earthquake that rocked San Francisco in 1906 is one of the biggest on record.

The state’s frequent seismic activity inspired Charles Richter to develop a way to measure them. This formula, which we know as the Richter Scale, records the magnitude of earthquakes and earth tremors. It’s roughly based on a factor of 10. In other words, a Category 4 earthquake isn’t a small increase from Category 3, it’s ten times the size.

Thanks to his work, scientists are able to categorize and study the phenomenon that literally shakes things up. On National Richter Scale Day, we celebrate the guy who helps us get a grip on an otherwise rocky world.

Today we also celebrate: National Audubon Day, National Dissertation Day, National Help a Horse Day, National Kids and Pets Day, National Pretzel Day, and National South Dakota Day.