The largest earthquake in recorded history struck Chile in 1960. It was a magnitude 9.5, and it killed 1,655 people and left 2 million homeless. A seismographic network records earthquakes, measuring the movement of the ground at a specific site. Magnitude measures the size of the earthquake source, providing the same number no matter where you are or what the shaking feels like. So what would happen if a magnitude 15 earthquake hit? That’s what xkcd’s What If? explored.
For a magnitude 10 earthquake to strike, a ruptured fault line 3,500 km long is needed, while a magnitude 11 earthquake would need a fault that goes halfway around the world. A magnitude 15 earthquake would be a million times more powerful, releasing enough energy to evaporate all of the water on the planet.
Taking things even further, a magnitude 18 earthquake would release around 1032 joules of energy, well enough to destroy the entire Earth. The sun could survive an earthquake up to a magnitude 24 earthquake, but a magnitude 25 would destroy the star. Fascinating stuff!
