What If a Magnitude 20 Earthquake Hits?

Would you sleep in this earthquake-proof bed? It senses when an earthquake is happening and drops you into a safe metal chamber. Yes, we know how ridiculous this looks. But desperate times call for desperate measures.

Because we’re about to experience the most powerful earthquake in history, a magnitude 20. How much damage would it cause? Would it break our planet into pieces? And what could cause such a massive earthquake?

To understand just how big a magnitude 20 earthquake would be, let’s take a look at the Richter scale. The Richter scale is a logarithmic scale that rates the amount of energy released by an earthquake.

What does logarithmic mean? In this case, it means that the amount of energy released increases 31.7 times between whole number values on the scale. For example, a 2.0ML [magnitude 2] quake is 32 times as energetic as a 1.0ML event. And a 3.0ML quake is 1,000 times more powerful than a 1.0ML event. The largest earthquake ever recorded registered a magnitude of 9.5, and it caused about five billion dollars in damage. It killed 1,655 people and left two million people homeless.

So how much worse would a magnitude 20 be? Would we have to evacuate the planet?

To properly prepare for an earthquake this big, we need to understand what causes earthquakes in general. Earthquakes are vibrations that travel through the crust of the Earth. They can be caused by events like volcanic eruptions and meteor impacts but the movement of tectonic plates is what usually causes them.

These plates, which make up the Earth’s crust, can slide against each other at a region called the transform boundary. When the plates move in different directions, they can cause a break in the Earth’s crust called a fault line. This is where most earthquakes take place.

The plates create friction as they push together tightly, and if there’s enough friction, they can become locked together and stop sliding. But the forces of the Earth will continue to push against them and increase the pent-up energy and pressure.

When the pressure builds up enough, it will overcome the friction and result in an intense and sudden shift. This causes the vibration we know as an earthquake. And the longer the fault line, the more massive the earthquake.

So how long of a fault line would be required to produce a magnitude 20 earthquake? Well, let’s put it this way. To produce a magnitude 10.5 earthquake, you’d need a fault length of about 80,000 km.

And given that the Earth’s circumference is only about 40,000 km, that would be highly unlikely. With all that considered, a magnitude 20 earthquake seems pretty impossible.
So there’s nothing to worry about.

Oh, right, except for that. One way that a magnitude 20 earthquake could occur would be due to a massive asteroid impact. An earthquake this large would last longer than any earthquake we have ever experienced.

You would feel the shaking for at least five minutes, and aftershocks would go on for hours. Tsunamis and volcanic eruptions would be taking place, more earthquakes would likely be triggered — and the whole world would be falling apart, literally.

For the power of this earthquake to destroy the planet, it would need to overcome something called the “gravitational binding energy,” which describes the minimum value a spherical and uniform object needs to keep together under the influence of gravity. Now, we won’t get into specific values here because we don’t want to make things any more complicated, so we’ll leave it at this, we’re screwed.

A magnitude 20 earthquake would produce more than enough energy to overcome the gravitational binding energy and destroy our planet. But the good news is that we would likely see the massive asteroid coming and would have time to prepare for everything that comes with it.