### Are Richter-magnitude 10 earthquakes possible?

• The largest earthquake since 1900 according to the United States Geological Survey (USGS) was Richter-9.5 magnitude quake in Chile in 1960. Are magnitude 10 earthquakes possible? If so, what is the most likely frequency of such earthquakes, and where are they the most likely to occur?

On a trip to Seattle I read on a plaque somewhere that there was a magnitude 10 earthquake. It was supposedly so powerful that it splintered forests and sent a tsunami over to Japan. Wikipedia's version is a little less cataclysmic http://goo.gl/yAhxk. As @Neo says it would likely be in a subduction zone.

Next question: can they go up to eleven?

No. Mw 10 earthquakes due to slip on faults are not possible as the length of the fault required will be greater the circumference of the earth.

Between 10 and 11, the seismic waves go all around the world and empty lakes on the other side of the planet. They wouldn't be due to an earthquake though, so perhaps seismic waves that big are possible but only from space collisions.

@stali would you be able to turn your comment into an answer?

7 years ago

Magnitude 10 earthquakes are indeed possible, but very very unlikely. You see the frequency of an Earthquake is given by the Gutenberg-Richter law:

\$\$N = 10^{a-bM}\$\$

where \$N\$ is the number of earthquakes \$\ge M (magnitude)\$ and \$a,b\$ are constants. As you can see, the greater \$M\$ is, the less \$N\$ is. \$a,b\$ are generally solved for statistically, through observational data and regression. But on face value, you can easily see that large magnitude earthquakes become less and less frequent on the exponential level.

As far as where a magnitude 10 earthquake could occur ? My guess is a subduction zone, as that is where the highest magnitude earthquakes tend to be. Which subduction zone? Anyone's guess is as good as mine, Chile or Tonga, though it is also important to note that earthquake magnitude is often related to fault size: I do not think there is a fault long/large enough to generate a \$ M \ge 10.0 \$ earthquake on Earth currently.

The G-R law with \$b\approx1\$ suggests that a 10.0 earthquake would happen about 30% as often as a 9.5 earthquake, so every 300-400 years doesn't seem unreasonable on that basis.