Problem with earthquake calculations

[Snakes]

Hello everyone thank you for taking the time to read this. I"ll try to keep it as brief as possible, as to not take up too much of your time. If you would like me to elaborate further please let me know.

I"ll quickly explain the method we currently use to calculate characters shaking a structure. When a character's energy is the origin point of an earthquake (eq). We determine how many joules are released with the magnitude of said eq. Then multiply that by the area that is affected.

The problem with this calculation is that the formula to convert the magnitude of an eq to joules has two constants that are specifically made for earth.
E= 10^1.5×(M)+4.8
Where E = energy in joules and M= magnitude richter.
1.5 is the coefficient. It’s there to account for energy scaling exponentially with amplitude. Basically it shows how energy really increases based on real life data on earthquakes. 4.8 is the constant that is used to make sure we get results that are accurate. Without it we would get wildly inconsistent results. This was also gathered by analysing real world eqs.

These constants are earth specific because they reflect earth rock rigidity. How seismic waves behave in earths crust and energy measurements from eqs that took place on earth. Given that applying this formula to shaking different structures let alone the vacuum of space. Simply leads to inaccurate results.

It's like trying to use a cars spedometer to calculate how fast the earth is spinning. It simply doesn't work.

I noticed that Floxy also made a thread talking about how eq formulas can't be used for different planets. Which seems relevant so I"ll link it here.

Assuming the above is accepted. The standard calculation for shaking the universe should be invalidated. I"ll link it here.

Thank you for reading and have a good day!

 

[Ghostimuscrime]

Following

 

[Damage3245]

@DontTalkDT @KLOL506 @Mr. Bambu @Agnaa @DMUA

This looks like it may be an important thread.

 

[Ecronicron]

Following. This could be important for many feats.

 

[Arkenis]

Are other rocky planets severely different from Earth's rock rigidity? Like the OP calc, how different is OP Earth's rock rigidity that we couldn't use the same formula?

 

[Lilybitdun]

Are other rocky planets severely different from Earth's rock rigidity? Like the OP calc, how different is OP Earth's rock rigidity that we couldn't use the same formula?

This thread covers more than just earthquakes on other planets, there's earthquakes on other structures and space as well

 

[Arkenis]

This thread covers more than just earthquakes on other planets, there's earthquakes on other structures and space as well

Sure but my question was merely about rocky planets since I noticed the OP calc had an issue with using r/110km. For other structures we can find the rigidity of stuff like wood or iron no? Isn't that just shear like how durability it is til it breaks?

 

[Snakes]

Sure but my question was merely about rocky planets since I noticed the OP calc had an issue with using r/110km. For other structures we can find the rigidity of stuff like wood or iron no? Isn't that just shear like how durability it is til it breaks?

The constants are derived from empirical data. So it would be very difficult if not impossible. To adjust the formula to a different planet. As we can't observe actual earthquakes in the world of One Piece.

So yes we do know rigidity of wood etc. But that alone isn't enough.

 

[Arkenis]

The constants are derived from empirical data. So it would be very difficult if not impossible. To adjust the formula to a different planet. As we can't observe actual earthquakes in the world of One Piece.

So yes we do know rigidity of wood etc. But that alone isn't enough.

So these constants can't be found for a planet like Mars? Are you saying that other rocky planets simply have widely different constants from Earth?

 

[Snakes]

So these constants can't be found for a planet like Mars? Are you saying that other rocky planets simply have widely different constants from Earth?

It has been found for a planet like Mars. Because we have the abbility to observe earthquakes that go on over there. We would not be able to do it for a planet in the next galaxy we can get no data on. Even if we know how big it is. It would just be conjecture.

It depends on the planet wheter or not the result would be widely different. But it certainly has the potential to be. Hence why I don't think we should be doing it.

Take for example a planet like in One Piece where it's compromised of far more water and less land than our planet. In that case the constants would certainly be entirely different. If it's just earth minus a few cities. Not so much.

 

[Ghostimuscrime]

I think there’s credence on Snakes’s claim, if another planet has different values than Earth then we can’t use Earth values to gauge them

If someone believes other planets would be vastly similar to Earth to the point of making the differences negligible I think it should be upto them to prove

 

[Arkenis]

I'm more just wondering what exactly are the constants for Earth.

 

[Lilybitdun]

I'm more just wondering what exactly are the constants for Earth.

The problem with this calculation is that the formula to convert the magnitude of an eq to joules has two constants that are specifically made for earth.
E= 10^1.5×(M)+4.8
Where E = energy in joules and M= magnitude richter.
1.5 is the coefficient. It’s there to account for energy scaling exponentially with amplitude. Basically it shows how energy really increases based on real life data on earthquakes. 4.8 is the constant that is used to make sure we get results that are accurate. Without it we would get wildly inconsistent results. This was also gathered by analysing real world eqs.

These constants are earth specific because they reflect earth rock rigidity. How seismic waves behave in earths crust and energy measurements from eqs that took place on earth. Given that applying this formula to shaking different structures let alone the vacuum of space. Simply leads to inaccurate results.

 

[Arkenis]

That doesn't answer my question or I'm just not seeing what the constant is.

 

[Lilybitdun]

That doesn't answer my question or I'm just not seeing what the constant is.

You're not seeing it
4.8 is the constant

 

[Snakes]

I'm more just wondering what exactly are the constants for Earth.

Imagine you have a spedometer for a car. It calculates the speed based on how big the tire is. The aerodynamics of the car, it's weight (not entirely accurate but just roll with the analogy).

If you then put the same spedometer on a bike it would say you're going 500 km/h. Because you're suddenly much lighter and it reads things incorrectly.

If you use the constants of earth for another planet. You get wild results like that.

The constants are dependent upon the gravity of the planet, rigidity of the materials, it's size etc. Then we analyse how earthquakes actually interact with the planet in real time. To make up the formula.

 

[Damage3245]

The OP's logic looks sound to me.

 

[Arkenis]

The constants are dependent upon the gravity of the planet, rigidity of the materials, it's size etc. Then we analyse how earthquakes actually interact with the planet in real time. To make up the formula.

So the constants are the gravity of the planet, the rigidity of the material and size numerically? Like Earth's grav is 9.8?

 

[Snakes]

So the constants are the gravity of the planet, the rigidity of the material and size numerically? Like Earth's grav is 9.8?

Those variables make it so that an earthquake interacts with a planet in a certain way. They then put a constant into the formula. That accounts for those specific factors on earth.

 

[Arkenis]

Those variables make it so that an earthquake interacts with a planet in a certain way. They then put a constant into the formula. That accounts for those specific factors on earth.

And what is the constant?

 

[Snakes]

And what is the constant?

The constant is just the number 4.8. Which ensured the formula gets accurate results. It's a known value in the formula. Just like how x is a variable

 

[Floxy178]

Agree with points in the OP, but I don't understand how this affects universe shaking calc as that uses earthquake formula on Earth, then applies ISL. It doesn't rely on "earthquake formula on different structure".

 

[KLOL506]

While the planetary sides seem moreso up DontTalkDT's alley, Floxy is right that our universe-shaking calcs don't rely on any Earthquake formulas for cosmic distances, just simple inverse square-law, and thus should be left out of this CRT.

 

[Qurbonboev]

Hello everyone thank you for taking the time to read this. I"ll try to keep it as brief as possible, as to not take up too much of your time. If you would like me to elaborate further please let me know.

So our variants are either:
1. Disregard any earthquake feats for planets significantly different from Earth by size, composition, gravity, etc.
2. Assume that such planets would nevertheless pocess qualities similar to Earth, even if it doesn't make physical sense. For example, IIRC, with Earth density, One Piece Planet would have 80g, which(I've heard) is contradicted by showings. And if it has same gravity as Earth, it would be mostly hollow or very lightweight in the core(which obviously would annihilate any chance to make meaningful earthquake calcs). If we want to make earthquake calcs, we would need to assume that this planet is somewhat magically able to have similar qualities to Earth. We would need to only account for changes that are clearly shown (like radius of planet).
Btw, what is source for three formulas of converting magnitude at distance to magnitude at origin(I need to find why exactly there is differences between r<60 km and r>700 km cases)?

 

[Floxy178]

Btw, what is source for three formulas of converting magnitude at distance to magnitude at origin(I need to find why exactly there is differences between r<60 km and r>700 km cases)?

Page 827

 

[Arkenis]

Not sure how relevant this is, but how is shaking different dimensions approached?

 

[Qurbonboev]

Page 827

I looked it up. Their formulas are empirical fit of data of this source: Richter, elementary seismology, 1958. What does original source itself says about them?:
"Another limitation of Table 22-1 is that without further evidence it cannot be assumed to apply outside the California area."
"It is difficult to extend Table 22-1 much beyond 600 kilometers for the
California area; earthquakes favorably placed for the purpose are not frequent, and there is good evidence of differences along different paths. In
general, assignment of magnitude at distances between 600 and 2000 kilometers is subject to numerous uncertainties, involves the effect of local crustal
structure, and can be approached only by way of special investigation for
each recording station."
I don't think this formula holds true for r>100,000 km.

Neither of sources elaborate why does relationship breaks that way with distance. My assumption would be that it's due to fact that at small distances earthquake can be approximated as moving as (mostly flat) surface. But with higher distances this approximation breaks(since Earth is not flat), and effect from it spherical form became stronger.
If this true, it probably means that we shouldn't use formula for 60<700 km case ever, because we can't be sure when does this model breaks in case of larger planet.
Only formula that probably could be used(if we assume same gravity, rock rigidity, mantle structure, etc.) is first one, for r<60 km

 

[Arkenis]

I looked it up. Their formulas are empirical fit of data of this source: Richter, elementary seismology, 1958. What does original source itself says about them?:
"Another limitation of Table 22-1 is that without further evidence it cannot be assumed to apply outside the California area."
"It is difficult to extend Table 22-1 much beyond 600 kilometers for the
California area; earthquakes favorably placed for the purpose are not frequent, and there is good evidence of differences along different paths. In
general, assignment of magnitude at distances between 600 and 2000 kilometers is subject to numerous uncertainties, involves the effect of local crustal
structure, and can be approached only by way of special investigation for
each recording station."
I don't think this formula holds true for r>100,000 km.

Neither of sources elaborate why does relationship breaks that way with distance. My assumption would be that it's due to fact that at small distances earthquake can be approximated as moving as (mostly flat) surface. But with higher distances this approximation breaks(since Earth is not flat), and effect from it spherical form became stronger.
If this true, it probably means that we shouldn't use formula for 60<700 km case ever, because we can't be sure when does this model breaks in case of larger planet.
Only formula that probably could be used(if we assume same gravity, rock rigidity, mantle structure, etc.) is first one, for r<60 km

Barely researched this, I only asked chatgpt for other countries like Japan or China and it gave me Kiyoo Wadati who developed the Wadati–Benioff zone concept which focuses on quakes up to the 700km in Japan.

 

[Mr. Bambu]

I wasn't aware we were using the EQ calc method for shaking random structures? Shaking like... a space station, obviously wouldn't use the EQ method. The OP is correct that it needs to be at least analogous to Earth to be usable.

I can't recall the shaking the universe calc but if it does use the EQ equation, I would agree that it is fundamentally wrong. I don't really agree with the "other planets are also invalid" thing unless said planets are explicitly not Earth-like, otherwise we can sort of assume their general composition being similar to ours, I reckon. That said, I will not touch a One Piece thread unless it's under threat of death, and even then it would need to be a fairly gruesome threat.

 

[Snakes]

Agree with points in the OP, but I don't understand how this affects universe shaking calc as that uses earthquake formula on Earth, then applies ISL. It doesn't rely on "earthquake formula on different structure".

Apologies for the late reply. To my understanding we still use the formula above to determine how much energy comes free in an earthquake. So even if we then apply the inverse square law wouldn't that still be falacious?

 

[Floxy178]

Apologies for the late reply. To my understanding we still use the formula above to determine how much energy comes free in an earthquake.

Just on Earth.

So even if we then apply the inverse square law wouldn't that still be falacious?

No because that part is irrelevant and doesn't rely on earthquake formula by itself.

 

[Snakes]

From what I'm gathering here when it pertains to structures and planets other than earth. This method of calculation should be rejected.

Do I need to get official votes on that? Damage and Mr.Bambu have already agreed.

 

[Snakes]

Just on Earth.

No because that part is irrelevant and doesn't rely on earthquake formula by itself.

I"ll quote from the calc itself below:

"Magnitude 3: 1.995262e+9 times 2.4320086e+54, 4.8524943e+63 Joules, 48.5249434325 Exafoe, Multi Solar System"

They're taking the energy as determined in an earthquake power chart. Which was created by the formula we're discussing. While referincing alabama quake. Inverse square law or not. They're still applying the energy output on earth across the entire universe.

 

[Mr. Bambu]

From what I'm gathering here when it pertains to structures and planets other than earth. This method of calculation should be rejected.

Do I need to get official votes on that? Damage and Mr.Bambu have already agreed.

I don't agree with the bit about "planets other than Earth". Most planets in most settings will probably be close enough to Earth-like that we can use EQ calcs fine. But in completely different settings- such as a space station, which I mentioned above, or some other object totally different from Earth- EQ would be a no-go. This includes the universe shaking calculation.

 

[KLOL506]

I am inclined to agree with Bambu. Even for planets larger than Earth but still retaining Earth-like properties, I think we can make an exception to be able to use the Earthquake formula for the lack of better options.

 

[Floxy178]

I"ll quote from the calc itself below:

"Magnitude 3: 1.995262e+9 times 2.4320086e+54, 4.8524943e+63 Joules, 48.5249434325 Exafoe, Multi Solar System"

They're taking the energy as determined in an earthquake power chart. Which was created by the formula we're discussing. While referincing alabama quake.

Yeah and the part that uses it doesn't contradict the requirement? If we use found value in a later step, it won't need same requirement when we're applying completely different formula.

Inverse square law or not. They're still applying the energy output on earth across the entire universe.

And what's problem with it? Unless someone's doing it via formula in question I don't see any problem referencing a value which doesn't have anything contradicting it in that step of calculation.

 

[Snakes]

I don't agree with the bit about "planets other than Earth". Most planets in most settings will probably be close enough to Earth-like that we can use EQ calcs fine. But in completely different settings- such as a space station, which I mentioned above, or some other object totally different from Earth- EQ would be a no-go. This includes the universe shaking calculation.

My apologies thank you for the clarification. I agree that if the planet is very similar like say in Bleach. It's completely fine. But hueco mundo which is entirely made up of sand. Really shouldn't be calced this way.

 

[Snakes]

I am inclined to agree with Bambu. Even for planets larger than Earth but still retaining Earth-like properties, I think we can make an exception to be able to use the Earthquake formula for the lack of better options.

The question then becomes where is the cap and what are earth like qualities. But perhaps that is a different thread? Or do we need to get into that?

 

[Mr. Bambu]

My apologies thank you for the clarification. I agree that if the planet is very similar like say in Bleach. It's completely fine. But hueco mundo which is entirely made up of sand. Really shouldn't be calced this way.

If a planet is made entirely of sand, sure. That would be a situation where I feel it would be fine to dismiss the calc method. The issue causing this thread, I believe, is One Piece, which to my understanding features an essentially Earth-like planet that is just large. In that instance, I would say that it is fine to use the EQ calc. Composition matters more to me than scope.

 

[Snakes]

Yeah and the part that uses it doesn't contradict the requirement? If we use found value in a later step, it won't need same requirement when we're applying completely different formula.

And what's problem with it? Unless someone's doing it via formula in question I don't see any problem referencing a value which doesn't have anything contradicting it in that step of calculation.

The reason for the lack of a contradiction is because we have no way of determining this formula or the eq chart for anything other than earth.

I mean no offense by this. But to me this sounds like well we got the first 10 numbers of pi incorrect. But if we just add a thousand more it will make up for it.

If the value you're using has absolutely nothing to do with what you're using it for. I.e. space. Applying the inverse square law is still rather meaningless in my eyes.