Addressing Earthquake calcs from Meteor Impacts

[SunDaGamer]

(aka JJK Downgrades Part 3 of 4)
I believe our Earthquake Calculations page could use a little more clarity on what sort of feats qualify for the Meteor Impact formula. It's rather concerning to me that calcs such as this (as well as any predecessors) and this have been using the Meteor Impact formula and were accepted for use. While the former may have the benefit of being named a meteor it still has issues of its own (which I'll get into down below) and the latter is the result of somebody being slammed into the floor from ground level.

Let's take a look at the paper (Collins et al., (2005) Earth Impact Effects Program) where we source our Modified Mercalli Intensity scale table from.

We can see where we derive our meteor impact formula, E = 10^((Richter Magnitude + 5.87)/0.67), from. We can also see that our energy result is the kinetic energy of the object when it impacts Earth, now this is important because this formula takes into account the kinetic energy energy losses that a meteor will face on impact after falling to Earth from deep space (hence the seismic efficiency being 0.0001%). The minimum speed of an object from deep space impacting the Earth is 11.2 km/s so when the meteorite impacts, a lot of energy is lost to crater excavation, plastic deformation and pressure waves (caused by the meteor compressing the air and ground below it as it moves at hypervelocity). This leads to calcs using the meteor impact formula yielding ~x10,000 higher results than the artificial earthquake formula for the same magnitude (which is justifiable with this context).

With all this in mind, let's go back to my original examples of misuse. You can see why it would be highly inappropriate to apply the meteor impact formula to feats like this where a meteor-like object is dropped from at most 300 meters off the ground slowly enough that subsonic characters can avoid getting crushed by dashing the last moment. Yet nobody had issues with this feat being calc'd using the meteor impact formula for the past 5 years. This is even more egregious when we go back to the second earthquake feat, which if you remember, is just a guy being slammed into the floor. Thus I believe our earthquake page should be more clear on what actually constitutes "an event very similar to a meteor." That being an object from deep space slamming into the Earth at hypervelocity and causing the environmental effects you'd expect from an impact at that speed.

It'd also help if we linked the Earth Impact Effects Program paper on the Earthquake Calculations page.

 

[KingTempest]

Sheesh

Streets said this is a CGM thread so I CGM'd it

 

[M3X_2.0]

JJK slander so good it affected the whole wiki

Following

 

[OjeTheArcher15]

Sun and Tempest landing critical hits to the jjk agenda (Superhuman and Street level is the plan)

 

[M3X_2.0]

Jokes aside, I largely agree with this. The core issue isn’t the formula itself, but the assumptions behind it.

The meteor impact formula is explicitly derived from deep-space impact scenarios, with extreme velocities and massive non-seismic energy losses. Applying it to low-altitude drops, subsonic impacts, or blunt-force slams breaks those assumptions entirely and inflates results by orders of magnitude.

I don’t think this requires banning the formula outright, but the Earthquake Calculations page should clearly define when a feat actually qualifies as “meteor-like” in a physical sense, not just visually.

Linking the Earth Impact Effects Program paper directly would also help prevent future misuse and make the intended context much clearer.

 

[Antvasima]

@DontTalkDT @Executor_N0

What do you think about this?

 

[Tago238]

Wait, how is it sourced from this paper? Do we use the online calculator this paper talks about making? Or was it just the best example of what the Mercalli intensity scale means?

I don't have time to read the whole thing but nothing in the seismic effects section seems to have been calculated or derived by the authors of the paper, they're just describing it there in a concise way. I accept the equation given comes from there and that they mentioned the stuff about "seismic efficiency", but it would be useful to see how stuff like that was found first and how it was discussed, as that could be relevant for arguing for certain verses.

For instance with JJK there's a precedent for characters saying their powers are weaker when spread out over larger ranges, which matches with the Jogo feat given since databooks talk about how it would "rend a town to ash" yet when he's actually using it to try and damage a powerful opponent it just blows up a side of a building. I'm not saying that saves the feat from the seismic efficiency concerns btw, I'm just saying more specific info is what would be needed for assessing if it is relevant at all. For instance I can def see air resistance experienced when entering the atmosphere not really being accounted for in the original.

EDIT: Someone on discord seemed to not get my point and I don't want this to become a JJK argument rn so I just want to make it clear: my issue is that the only relevant section of this paper to what's being talked about is a very short section that doesn't seem to be particularly tied into the derivations or arguments given earlier in the paper. Instead it's largely just describing previous work (or putting previous work together into one equation, but I'm not even sure that's original) to make a few equations explicit. The physical arguments at play for the equation being talked about appears largely unreferred to, so we can't argue about it until we've read those other papers. While experimental, I'd imagine these papers provide better discussion of the physics and also would- for instance- tell us if it's working out the impactor's KE before entering the atmosphere or when colliding with a surface.

 

[Tago238]

To cap it off, I think we all understand that any impactor is not going efficiently transfer energy to seismic energy- and having an equation that relates seismic energy to impactor kinetic energy would be great. The question of this thread is if the meteor equation effectively describes it for most objects or even for fictional "pseudo-meteors", and I also think it is a question unanswered by what has been posted so far.

 

[DontTalkDT]

We can also see that our energy result is the kinetic energy of the object when it impacts Earth, now this is important because this formula takes into account the kinetic energy energy losses that a meteor will face when it impacts after falling to Earth from deep space (hence the seismic efficiency being 0.0001%).

It says that it is the kinetic energy of the impact, so I'm fairly sure that is after passing through the atmosphere. So energy loss via air resistance is not part of the seismic efficiency.
You could confirm that with the calculator.

The seismic efficiency in my understanding is about the translation of KE at impact to shacking. I.e. it accounts for energy that isn't used to shake the ground, but to instead do things like break the ground and the meteor apart and to launch rock away to create the crater.

 

[SunDaGamer]

It says that it is the kinetic energy of the impact, so I'm fairly sure that is after passing through the atmosphere. So energy loss via air resistance is not part of the seismic efficiency.

I believe I did edit the op to make that clearer.

The falling from deep space part is only relevant because it means meteors will have picked up immense speed from accelerating toward the Earth and hit the ground at hypervelocity which is what causes those massive transfers of kinetic energy to heat energy and sound energy on impact (smaller meteors do hit the Earth at terminal velocity instead but the resulting seismic waves are pretty insignificant, KE from stuff like the Hoba meteorite would be 8-C)

 

[SunDaGamer]

For clarity, here is how the formula is derived:
We start with the Gutenberg-Richter magnitude-energy relation, log10(E) = 1.5M + 4.8 (this is where our artificial earthquake formula is derived from)
where E is seismic energy and M is seismic magnitude

since seismic energy is a fraction of the kinetic energy, we get Eseismic = kEimpact where k is our seismic efficiency
log10(kEimpact) = 1.5M + 4.8
log10(Eimpact) = 1.5M + 4.8 - log10(k)

substituting in k≈10^-4
log10(Eimpact) = 1.5M + 4.8 - log10(10^-4)
log10(Eimpact) = 1.5M + 8.8
(log10(Eimpact) - 8.8)/1.5 = M
M = 0.67log10(Eimpact) - 5.87

Of course, we can rearrange to make Eimpact the subject
M + 5.87 = 0.67log10(Eimpact)
(M + 5.87)/0.67 = log10(Eimpact)
Eimpact = 10^((M + 5.87)/0.67) this is how we get the meteor impact formula on our page

As for how k is obtained, papers written on this subject cite the figures obtained in Schultz and Gault (1975), which you can find and download here, k had a range of 10^-3 to 10^-5 so the geometric mean of 10^-4 was commonly adopted which we can see in papers like Melosh (1989)

If we have enough information about a meteor impact that we are able to find sufficient parameters (impactor mass, impactor velocity, properties of the material impacted, crater dimensions, stress pulse duration, wave attenuation, frequency spectrum) to calculate k for a specific instance (which is unfeasible for us measly powerscalers) then we would already be able to determine the Kinetic Energy of the meteor impact. If you've already solved energy, working backward from inferred earthquake magnitudes using Mercalli descriptors would be unnecessary and an inferior method.

Do we use the online calculator this paper talks about making?

We literally link it on the Earthquake page along with instructions on how to use it to find what the (kinetic) energy of your theoretical meteor would be before atmospheric entry

 

[Arkenis]

this

https://vsbattles.fandom.com/wiki/User_blog:ElJoaki5/Jujutsu_Kaisen:_Inumaki’s_Crater

This one too I think follows the meteor impact.

 

[Tago238]

What I'm getting from Schultz and Gault paper is that they very clearly have some straightforward equations we could easily use to derive seismic efficiency for a variety of impactors (doesn't seem to have any relevance to passing through the atmosphere at all mind you, which is good, since it's referring to craters on the moon and mercury), however I don't feel totally confident in my understanding of the physics presented in the equations provided (tbh, waves are a bit of a distant memory for me now they haven't showed up much in school for a while). I don't know if anyone else feels more confident about using the terms provided?

I think it would be good if we still had an equation for distinguishing between instances of efficient transfer to seismic energy and instances where seismic effects are incidental to an impactor hitting a surface, rather than this being arbitrarily only acknowledged for realistic-looking meteors. That's the ideal, at least.

 

[Buraqibear]

Bump

 

[Anonymous_Learner]

bump

 

[Electronic74947]

https://vsbattles.fandom.com/wiki/User_blog:ElJoaki5/Jujutsu_Kaisen:_Inumaki’s_Crater

This one too I think follows the meteor impact.

shit feat anywats. Just calc the hole in the ground

 

[Arkenis]

shit feat anywats. Just calc the hole in the ground

It was just building level, calcing the earthquake could be higher.

 

[Electronic74947]

It was just building level, calcing the earthquake could be higher.

I think it was recalced to MCB via the anime and pulverisation end?

 

[Arkenis]

Anime doesn't matter

 

[Electronic74947]

Anime doesn't matter

Dont we accept the jjk0 movie as canon tho

 

[Arkenis]

I don't remember why.

 

[Electronic74947]

I don't remember why.

don't remember why it's canon or?

 

[Arkenis]

don't remember why it's canon or?

Nah. A crt might've been made a while back or we just granted it not sure but it may be invalid given the new canon criteria.

 

[Electronic74947]

Nah. A crt might've been made a while back or we just granted it not sure but it may be invalid given the new canon criteria.

There were a lot of anime original scenes like nanami achieving his record and yuta hitting the black flash in the fight. Need to double check though

 

[Tago238]

This is very off topic for what's supposed to be a site wide revision.

 

[M3X_2.0]

Definitely not getting the appropriate attention.

 

[Robo432343]

Definitely not getting the appropriate attention.

use your ping powers

 

[Arkenis]

Where art thou JJK supporters in such strenuous times? Art thou not moved by endless BUMPS?
bump

 

[Buraqibear]

Where art thou JJK supporters in such strenuous times? Art thou not moved by endless BUMPS?
bump

The JJK supporters are either too lazy or too busy wanking on the discord
bump

 

[Qurbonboev]

The seismic efficiency in my understanding is about the translation of KE at impact to shacking. I.e. it accounts for energy that isn't used to shake the ground, but to instead do things like break the ground and the meteor apart and to launch rock away to create the crater.

The minimum speed of an object from deep space impacting the Earth is 11.2 km/s so any meteor will face extreme levels of friction with the air as it enters the atmosphere, then when the meteor finally impacts even more energy is lost to crater excavation, plastic deformation and pressure waves (caused by the meteor compressing the air and ground below it as it moves at hypervelocity)

Impactors that experience intense loss of energy from friction in atmosphere, usually don't reach ground.
Main culprit of low seismic efficiencies is: most of impactor energy being wasted on vaporisation of ground and impactor itself during impact, creation of crater, radiation, launch of ejecta (which can have enough speed to reach Moon), atmospheric shockwaves. And feats that currently use this formula usually don't showcase these processes at all.
Standards of what constitutes "an event very similar to meteor impact" should be much stricter

 

[Arkenis]

bump. Is just dead?

 

[Tago238]

I forgot if this was something I needed permission to post in

 

[Antvasima]

@Mr. Bambu @Therefir @DMUA @Damage3245 @TheRustyOne @Armorchompy @Migue79 @Psychomaster35 @KLOL506 @Dark-Carioca @AbaddonTheDisappointment @Aguywhodoesthings @Agnaa @Dalesean027 @DemiiPowa @Flashlight237 @SeijiSetto @Naito-desu @Floxy178 @ElJoaki5 @Drite77

Your help would also be very appreciated here.

 

[KLOL506]

Not my area of expertise, but I know DontTalkDT and Executor_N0 hold experience in this regard.

 

[Antvasima]

Yes, but I pinged them here earlier.

 

[Dalesean027]

Bump

 

[Qurbonboev]

Bump

Could you share your own opinions and suggestions on this topic?

 

[NeverForgett]

Don't meteors lose most of their velocity due to atmospheric drag, so when they hit the crust, they're a fair bit slower?

Atmospheric entry - Wikipedia

en.wikipedia.org

Sometimes they'll decelerate from 2-4 km/s.

So I think we should re-work the values.

 

[NeverForgett]

Bump

I see you're calculation group, could you look at this calculation: https://vsbattles.fandom.com/wiki/User_blog:NeverForgett/Meruem_destroys_a_mountain

 

[SunDaGamer]

Don't meteors lose most of their velocity due to atmospheric drag, so when they hit the crust, they're a fair bit slower?

Atmospheric entry - Wikipedia

en.wikipedia.org

Sometimes they'll decelerate from 2-4 km/s.

So I think we should re-work the values.

Addressing Earthquake calcs from Meteor Impacts

(aka JJK Downgrades Part 3 of 4) I believe our Earthquake Calculations page could use a little more clarity on what sort of feats qualify for the Meteor Impact formula. It's rather concerning to me that calcs such as this (as well as any predecessors) and this have been using the Meteor Impact...

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