<p>A planet-ripping earthquake isn't possible on Earth.  For a magnitude 10.5 Richter scale earthquake, one would need twice the fault lines that exist on Earth according to the <a href="https://www.usgs.gov/natural-hazards/earthquake-hazards/science/earthquake-magnitude-energy-release-and-shaking-intensity?qt-science_center_objects=0#qt-science_center_objects" rel="noreferrer">USGS</a>.</p>
<p>The same website relates energy <span class="math-container">$E$</span> in joules to earthquake magnitude <span class="math-container">$M$</span> with Baths equation: <span class="math-container">$log E = 5.24 + 1.44M$</span>.  A 10.5 magnitude earthquake would produce about 2.29e20 joules of energy.  The Earth's <a href="https://en.wikipedia.org/wiki/Gravitational_binding_energy" rel="noreferrer">gravitational binding energy</a> is about 2e32 joules. So if all possible earthquakes went off at the same time twice, it would only generate a trillionth of the energy necessary to rip the planet apart. Earthquakes occur just under the surface of the earth, and they release their energy over time. So, even if an earthquake could generate 2e32 joules of energy, it wouldn't be sufficiently directed to destroy the planet.</p>
<p>Earthquakes are the product of built up energy in tectonic plates by convecting magma.  This is a small effect compared to the power of gravity. The IAU requires a planet to have &quot;sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.&quot; That means gravity is a dominant force over the rigidity of the materials that compose the planet. But the <a href="https://en.wikipedia.org/wiki/Seismic_moment" rel="noreferrer">seismic moment</a> is governed by the <a href="https://en.wikipedia.org/wiki/Shear_modulus" rel="noreferrer">modulus of rigidity</a> of the materials. So localized earthquake forces and energies will be small compared to the gravitational forces from the planet itself.  So, we wouldn't expect planet ripping earthquakes on exo-planets either.</p>
<p><strong>Notes:</strong></p>
<ol>
<li><p>If we consider nuclear fusion as a source of quakes, then supernovas might be called star-ripping quakes.</p>
</li>
<li><p>If we consider collisions as a source of quakes, then the asteroid <a href="https://en.wikipedia.org/wiki/16_Psyche" rel="noreferrer">16 Psyche</a> might be an example of a proto-planet destroyed by earthquakes.</p>
</li>
</ol>

CC BY-SA 4.0
2020-12-15T22:58:40.607Z
Thanks for the very conclusive arguments. In the meantime I also found https://www.quora.com/How-large-does-an-earthquake-have-to-be-to-destroy-the-Earth where people calculate that we need a quake of magnitude 18.4 to rip our pretty blue planet apart.
B--rian
CC BY-SA 4.0
2020-12-11T15:15:01.400Z
2020-12-11T15:32:28.647Z
2020-12-11T15:32:28.647Z
Connor Garcia
<p>The <a href="https://en.wikipedia.org/wiki/Gutenberg%E2%80%93Richter_law" rel="nofollow noreferrer">Gutenberg-Richter-Law</a> is a very-well studied relationship between the magnitude and total number of (earth)quakes. In theory, there is no upper bound for the size of a quake other than the size of the planet. In other words: There is a non-zero probability (which is rather low) that a quake can rip appart the whole planet. There are numerical evidences with toy models such as the <a href="https://en.wikipedia.org/wiki/Olami%E2%80%93Feder%E2%80%93Christensen_model" rel="nofollow noreferrer">Olami–Feder–Christensen model</a> suggest, such things can really happen.</p>
<p>Therefore my question: <strong>Are they any hints for (exo)planet-destroying quakes?</strong> And what about star-quakes which occur during stationary phases of star evolution?</p>
<h2>References</h2>
<ul>
<li><a href="https://arxiv.org/abs/cond-mat/0608324" rel="nofollow noreferrer">cond-mat/0608324: Transient and stationary behavior of the Olami-Feder-Christensen earthquake model</a> - not the publication which claims that planet-destroying quakes are possible, but a possible introduction to the kind of numerical methods used</li>
</ul>

CC BY-SA 4.0
2020-12-09T21:29:39.840Z
I don't believe the statement that "a quake can rip appart the whole planet." Earthquakes are sudden releases of built up energy.  By what mechanism could enough energy be produced, stored, and suddenly released that would overcome a planet's gravitational binding energy?
Connor Garcia
CC BY-SA 4.0
2020-12-09T21:54:39.600Z
@ConnorGarcia I share your concern. I will try to find the scientific publication of the OFC-model who claimed that such planet-quakes are possible. I mean, computer simulations on a large number ensemble shows that there are indeed quakes which have the size of the system. The paper interpreted that as planet-destroying quakes, as far as I remember, and that sounded cool, but I am wondering whether they really exist.
B--rian
CC BY-SA 4.0
2020-12-09T22:03:02.573Z
I agree. It might improve your question to (1) include a reference to the paper, and (2) ask if planet-destroying earthquakes are really possible.  If they aren't possible, it may not make sense to ask for examples.
Connor Garcia
CC BY-SA 4.0
2020-12-09T22:10:24.010Z
@ConnorGarcia I already included on reference, but I will have to search for the one with the claim.
B--rian
CC BY-SA 4.0
2020-12-09T22:52:58.570Z
Just because the measurement scale for earthquakes has no inherent upper bound doesn't mean that earthquakes have none. Their upper bound is in the strength of the material - and it is thought that quakes much larger than the 1962 quake in Chile are not possible as it would rupture before (and actually you can consider that a sequence of several quakes even). A theoretical earthquak which ruptures once around Earth would be like magnitude ~14 (IIRC) - yet it's not physically possible to just twist, e.g. the upper half against the lower; it would be like a stone jumping into the air.
planetmaker
CC BY-SA 4.0
2020-12-10T22:48:43.643Z
@planetmaker Very insightful comment, thanks. Just a minor follow-up: How did you obtain magnitude 14 for a earthquake rupturing the planet?
B--rian
CC BY-SA 4.0
2020-12-10T22:55:45.237Z
@B--rian the calculation is as such that you calculate the energy for a rupture once around the planet with a typical displacement (say 1m) - and then take the conversion of energy to seismic moment to get the magnitude (seismic moment magnitude is calibrated such that it fits the usual Richter scale for the type of Earthquake typical in California). You could also take the energy from, e.g. the Chile quake with its 2000km length and 9.6magnitudes and extrapolate that  by similar means.
planetmaker
<exoplanet><quake><star-evolution>
Are planet-destroying quakes possible or observable?
B--rian
# Are planet-destroying quakes possible or observable?

(Asked by: username_0 on 2020-12-09)

The [Gutenberg-Richter-Law](https://en.wikipedia.org/wiki/Gutenberg%E2%80%93Richter_law) is a very-well studied relationship between the magnitude and total number of (earth)quakes. In theory, there is no upper bound for the size of a quake other than the size of the planet. In other words: There is a non-zero probability (which is rather low) that a quake can rip appart the whole planet. There are numerical evidences with toy models such as the [Olami–Feder–Christensen model](https://en.wikipedia.org/wiki/Olami%E2%80%93Feder%E2%80%93Christensen_model) suggest, such things can really happen.

Therefore my question: **Are they any hints for (exo)planet-destroying quakes?** And what about star-quakes which occur during stationary phases of star evolution?

## References

* [cond-mat/0608324: Transient and stationary behavior of the Olami-Feder-Christensen earthquake model](https://arxiv.org/abs/cond-mat/0608324) - not the publication which claims that planet-destroying quakes are possible, but a possible introduction to the kind of numerical methods used

**Tags:** exoplanet, quake, star-evolution
> **Comments:**
> **username_1**: I don't believe the statement that "a quake can rip appart the whole planet." Earthquakes are sudden releases of built up energy.  By what mechanism could enough energy be produced, stored, and suddenly released that would overcome a planet's gravitational binding energy?  
> **username_0**: @ConnorGarcia I share your concern. I will try to find the scientific publication of the OFC-model who claimed that such planet-quakes are possible. I mean, computer simulations on a large number ensemble shows that there are indeed quakes which have the size of the system. The paper interpreted that as planet-destroying quakes, as far as I remember, and that sounded cool, but I am wondering whether they really exist.  
> **username_1**: I agree. It might improve your question to (1) include a reference to the paper, and (2) ask if planet-destroying earthquakes are really possible.  If they aren't possible, it may not make sense to ask for examples.  
> **username_0**: @ConnorGarcia I already included on reference, but I will have to search for the one with the claim.  
> **username_2**: Just because the measurement scale for earthquakes has no inherent upper bound doesn't mean that earthquakes have none. Their upper bound is in the strength of the material - and it is thought that quakes much larger than the 1962 quake in Chile are not possible as it would rupture before (and actually you can consider that a sequence of several quakes even). A theoretical earthquak which ruptures once around Earth would be like magnitude ~14 (IIRC) - yet it's not physically possible to just twist, e.g. the upper half against the lower; it would be like a stone jumping into the air.  
> **username_0**: @planetmaker Very insightful comment, thanks. Just a minor follow-up: How did you obtain magnitude 14 for a earthquake rupturing the planet?  
> **username_2**: @B--rian the calculation is as such that you calculate the energy for a rupture once around the planet with a typical displacement (say 1m) - and then take the conversion of energy to seismic moment to get the magnitude (seismic moment magnitude is calibrated such that it fits the usual Richter scale for the type of Earthquake typical in California). You could also take the energy from, e.g. the Chile quake with its 2000km length and 9.6magnitudes and extrapolate that  by similar means.  

---

## 1 answers

### Answer by username_1 on 2020-12-11. Score: 7 | Accepted answer

A planet-ripping earthquake isn't possible on Earth. For a magnitude 10.5 Richter scale earthquake, one would need twice the fault lines that exist on Earth according to the [USGS](https://www.usgs.gov/natural-hazards/earthquake-hazards/science/earthquake-magnitude-energy-release-and-shaking-intensity?qt-science_center_objects=0#qt-science_center_objects).

The same website relates energy $E$ in joules to earthquake magnitude $M$ with Baths equation: $log E = 5.24 + 1.44M$. A 10.5 magnitude earthquake would produce about 2.29e20 joules of energy. The Earth's [gravitational binding energy](https://en.wikipedia.org/wiki/Gravitational_binding_energy) is about 2e32 joules. So if all possible earthquakes went off at the same time twice, it would only generate a trillionth of the energy necessary to rip the planet apart. Earthquakes occur just under the surface of the earth, and they release their energy over time. So, even if an earthquake could generate 2e32 joules of energy, it wouldn't be sufficiently directed to destroy the planet.

Earthquakes are the product of built up energy in tectonic plates by convecting magma. This is a small effect compared to the power of gravity. The IAU requires a planet to have "sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape." That means gravity is a dominant force over the rigidity of the materials that compose the planet. But the [seismic moment](https://en.wikipedia.org/wiki/Seismic_moment) is governed by the [modulus of rigidity](https://en.wikipedia.org/wiki/Shear_modulus) of the materials. So localized earthquake forces and energies will be small compared to the gravitational forces from the planet itself. So, we wouldn't expect planet ripping earthquakes on exo-planets either.

**Notes:**

1. If we consider nuclear fusion as a source of quakes, then supernovas might be called star-ripping quakes.
2. If we consider collisions as a source of quakes, then the asteroid [16 Psyche](https://en.wikipedia.org/wiki/16_Psyche) might be an example of a proto-planet destroyed by earthquakes.

> **Comments:**
> **username_0**: Thanks for the very conclusive arguments. In the meantime I also found https://www.quora.com/How-large-does-an-earthquake-have-to-be-to-destroy-the-Earth where people calculate that we need a quake of magnitude 18.4 to rip our pretty blue planet apart.  

---

