Back in the early days of studying earthquakes, scientists needed to be a little creative to test their theories while trying to get readings.
Emil Wiechert, a German physicist and geophysicist, had a theory that seismic waves would allow us to see inside the earths surface. He was never able to fully test his theory, but his assistant, Ludger Mintrop, discovered that dropping a four-ton steel ball from a 46-feet in the air created tiny earthquakes.
As you can see in the clip, it drops with some serious power. Every year, the crater it creates has to be refilled so it can be dropped again.
The grund underneath the ball actually steams once it hits because of the heat created from the impact.