Could An Earthquake Ever Crack Open A Planet?

Is this possible via an earthquake? Yes - but perhaps not in the way you might think. Vadim Sadovski/Shutterstock

An interesting question came up in a discussion about earthquakes recently – namely, could one ever be powerful enough to fracture the planet, or even completely break it apart? This is a surprisingly difficult question to answer, but let’s take a look at the science to see how possible this type of apocalypse really is.

First off, let’s just remind ourselves what causes an earthquake and just how ludicrously energetic they are at their worst. There are so many different ways to get earthquakes – even the Moon’s gravitational pull can trigger them, for goodness’ sake – but for the sake of simplicity, we’ll stick to the most common for now.

You’ve got fault networks like the San Andreas complex, which has formed at the point where the Pacific Plate is moving northwards with respect to the North American Plate. This type of tectonic margin is called a “transform” boundary, and it tends to produce very shallow and damaging earthquakes.

Then you’ve got two plates coming together to collide. On these “convergent” boundaries, one of two things happens: either the denser plate sinks beneath the other one and gets destroyed in the mantle (see: Japan Trench) or they both smash into each other and rise up to form a mountain range (see: Himalayas).

In the case of the former, you get deep-seated earthquakes, and in terms of the latter, they are at middling-to-shallow depths. With some exceptions, these are how earthquakes are generated on Earth, so how powerful can they get?

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A map of the tsunami generated by the world's most powerful earthquake. Each contour represents one hour of travel time. NOAA

Here are the top five most powerful earthquakes on record, in ascending order:

5 – Kamchatka, former Soviet Union: 9.0M (November 4, 1952) on a convergent fault along the Kuril-Kamchatka trench. It created a devastating tsunami, and over 2,300 people perished.

4 – Tohoku region, off the eastern coast of Japan: 9.1M (March 11, 2011) on a convergent fault along the West Pacific boundary between the North American and Pacific Plates. The tsunami was one of the deadliest in human history, killing up to 20,000 people.

3 – Sumatra, Indonesia: 9.2M (December 26, 2004) on a convergent fault where the Indian Plate slides beneath the Burma Plate. Scary fact: , At one point, the rupture was moving 2.8 kilometers (1.7 miles) per second, which equates to speeds of 10,000 kilometers (6,200 miles) per hour. The resulting tsunami caused up to a quarter of a million deaths.

2 – Prince William Sound, Alaska: 9.2M (March 27, 1964) on a convergent fault along the Aleutian Trench. Despite a powerful tsunami, just 30 or so people died.

1 – Valdivia, Chile: 9.5M (May 22, 1960) on a convergent fault between the descending Nazca Plate and the South American Plate. It also produced a colossal, Pacific Ocean-wide tsunami, but “only” 1,000-6,000 people died.

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