Big Shake Feats

[Agnaa]

There are some feats where a moderately large reason is shaken, but which don't qualify as earthquakes.

In lieu of being able to use the methods on the Earthquake Calculations page, some people have calculated them as Kinetic Energy Feats, such as this calculation. Treating the entire mass which was involved in the shaking as having been moved at a certain velocity.

We previously had a thread about similar methods being used for shockwaves going through the air. Disqualifying them because not the entire mass is moved at that velocity; a small portion of it gets the energy, which moves and passes that energy onto another small portion before settling back into its original position, and so on. I believe that same issue exists here.

I also believe that a lot of these sorts of feats, where a character hits the ground causing the surroundings to shake, often run afoul of our standard for Kinetic Energy Feats regardless, as they usually don't show destruction of the ground in-line with the values found through the kinetic energy of shaking that area.

I think that, to rectify this, we should add some text to the Earthquake Calculations page, disqualifying this sort of thing. The Overview currently says:

For the purpose of these calculations shaking a minor area should not be assumed to automatically translate to an earthquake. Either a large area being shaken or evidence that we are dealing with something earthquake-like and not just some minor shaking would be needed.

We can expand that to:

For the purpose of these calculations shaking a minor area should not be assumed to automatically translate to an earthquake. Either a large area being shaken or evidence that we are dealing with something earthquake-like and not just some minor shaking would be needed. Feats of shaking which are not earthquake like cannot be feasibly calculated, and should absolutely not be calculated using Kinetic Energy of the mass that was shaken, as this does not properly correspond to the energy required to shake large objects.

 

[Agnaa]

@DontTalkDT @Dark-Carioca @SeijiSetto @DMUA @Therefir

 

[Damage3245]

Seems to make sense to me.

 

[DontTalkDT]

The first method seems wrong primarily because the amplitude is an absolute high end and the frequency calculation (as far as I can tell) makes no sense, as well as frequency and amplitude not being incorporated into a wave energy formula the right way.

In principle, I do think some small-scale shacking feats can be calculated. Namely, if it's an enduring shacking (not just a shockwave passing through) that affects the entire structure simultaneously, then you can probably use this table to get a velocity and use KE based on that for a result.

 

[Agnaa]

In principle, I do think some small-scale shacking feats can be calculated. Namely, if it's an enduring shacking (not just a shockwave passing through) that affects the entire structure simultaneously, then you can probably use this table to get a velocity and use KE based on that for a result.

I'm still not sure about that. An enduring shaking that affects the entire structure at once could come about from resonance, multiple shocks reverberating back and forth, taking a while to die down.

Although, thinking about some practical examples (how one or two people can get a car to noticeably shake), using that table involves such a small velocity that it ends up rounding down to values that I'd even describe as astonishingly low (only 2.5 joules for shaking a car moderately). I guess that wouldn't wank things, at least, but it still seems a bit unreliable; maybe don't allow that method to establish anti-feats? Eugh.

 

[DMUA]

We previously had a thread about similar methods being used for shockwaves going through the air. Disqualifying them because not the entire mass is moved at that velocity; a small portion of it gets the energy, which moves and passes that energy onto another small portion before settling back into its original position, and so on. I believe that same issue exists here.

I wasn't quite aware of this, but yeah I agree with the principle applying now that you've laid it all out

 

[DontTalkDT]

I'm still not sure about that. An enduring shaking that affects the entire structure at once could come about from resonance, multiple shocks reverberating back and forth, taking a while to die down.

That would not be enduring shaking then, though, but repeated shaking. Of course, if the repeats become frequent enough one might not be able to tell the difference anymore, but as the time between repeats decreases, it should also get closer to the full shacking value.

Although, thinking about some practical examples (how one or two people can get a car to noticeably shake), using that table involves such a small velocity that it ends up rounding down to values that I'd even describe as astonishingly low (only 2.5 joules for shaking a car moderately). I guess that wouldn't wank things, at least, but it still seems a bit unreliable; maybe don't allow that method to establish anti-feats? Eugh.

Cars also work way different due to not being rigid and stuff. For something like a car you are better off calculating it like a spring with a weight.
But yeah, I wouldn't take the method as precise enough for anti-feats.

 

[Agnaa]

Well, if you come up with a good way to paint a picture of what should be enduring shaking, I can reword my suggestion to be less total, and suggest your method in cases of enduring shaking (with a caveat to not use it for anti-feats).

 

[Qurbonboev]

Hello. I want help with this calc, that CGM seemed invalid due to changes brought up in this thread.
To start off: displacement and acceleration from this shaking would be extreme(X+ on this table). And since vibration spread out with speed of sound in respective materials, vibration would envelop entirety of lab in less than 1 frame. And one strike usually causes several shakes after it.
Could we still use old formula for calculating this feat? What are alternative methods for calculating this?

 

[Qurbonboev]

Snip

Snip

Sorry if I am bothering you. You two seemed to be most active here. What you both think of feat?

Snip

 

[Qurbonboev]

Bump

 

[Qurbonboev]

Bump

 

[Dalesean027]

@DontTalkDT
@Agnaa
@Antvasima

 

[Antvasima]

What do you need help with here?

 

[Dalesean027]

This important calc thread was never properly concluded and does effect how we treat 'shaking' feats in calcs on wiki

So we still need some CGMs here

 

[Agnaa]

@Agnaa

Welp, I'm going through mental health issues involving loss of interest in most things, including battleboarding.

Based on historical experiences, I'll probably get back into the swing of things in 1-9 months, but until then I won't be engaging in anything that requires more than the absolute minimum of effort, or is of the utmost criticality.

 

[Dalesean027]

Understandable, I wish you the best in your endeavors

 

[Qurbonboev]

So to recap things:
Agnaa brought up valid points against our current usage of formula. But mainly: shaking doesn't always effect entire structure at once, so usage of the formula is incorrect. DontTalkDT brought up some alternative methods for replacement. But thread wasn't properly concluded at all. (And some calcs were already rejected, using this (unfinished) thread as justification, while not giving alternative formulas, which isn't optimal).

To give a concrete example: this feat. Character strikes (presumably metal walls), and it results in shaking of big (and obviously rigid) structure. It's pretty obvious given pretty extreme velocities and acceleration in work here, that entire structure was shaken an once, otherwise it would be teared off(specific calc for it is here). And shaking continues for some short time after each strike
Can we still use old formula for calculating this feat? Can we use something like: calculating speed of displacement, assume that it affected at least entire structure at once(otherwise it would broke down), and thus calculate it KE?
Example is specific, but most shaking feats should be similar to it. Since they usually involve shaking of big and rigid structures.

Snip

Taging DTD, since they proposed alternative method

Snip

 

[Vzearr]

I'll help out just give me a few to think.

 

[Vzearr]

Okay, so KE doesn't work that well despite using ground acceleration. If you shake the ground, the shaking is never going to have an equal speed all around; you'd need a slightly changed formula.

So, lets create one!

Kinetic Energies formula is as follows.
0.5 · m · v²

So, the mass which is the ground is moving. However it's a **** ton of mass and they all move at different speeds so we cant really calculate it as if they all move at the same speed. So we get to use calculus (yay).

Think of it like it's a crowd of people instead of one large person. We'd calculate the crowd of people running much differently, we would of course calculate their KE separately but lets say its all the humans on earth, that's, of course, impractical, so we'd do something else.

To account for this, the system need to be treated as a continuous medium, where each volume element contributes its own kinetic energy.

Overall, I've come to the formula:

Eₖ = ∭ (1/2) ρ(r) · v(r, t)² dV

Where:

• ρ(r) is the material density
• v(r, t) is the local speed at each spot
• dV is the volume element

• For speed I'll be using this
• For density I'll use concrete
• I'll assume a 1 by 1 by 1 meter area.

For a simple non uniform approximation, assume the shaking decreased linearly with depth across a 1×1×1 meter volume, such that:

v(z) = 4.65(1 − z) for 0 ≤ z ≤ 1

Then we would get

Assumeing the density is constant at:

ρ = 2700 kg/m³

Then:

Eₖ = ∭ (1/2) ρ v(z)² dV

Since dV = dx dy dz, this becomes:

Eₖ = ∭ (1/2)(2700)[4.65(1 − z)]² dx dy dz

For a 1×1×1 meter region:

Eₖ = (1/2)(2700)(4.65)² ∫₀¹ ∫₀¹ ∫₀¹ (1 − z)² dx dy dz

Since the integrand does not depend on x or y, those integrals each evaluate to 1:

Eₖ = (1/2)(2700)(4.65)² ∫₀¹ (1 − z)² dz

Now evaluate the last few integrals:

∫₀¹ (1 − z)² dz = 1/3

So:

Eₖ = (1/2)(2700)(4.65)² (1/3)
Eₖ = (1/2)(2700)(21.6225)(1/3)
Eₖ = 9730 Joules

 

[Schattenbach]

Ground based quakes are quite complex. Here's a quick refresher/inside look. If the location, as well as the material and layer structure the ground is made up of wouldn't matter, seismology wouldn't function as explorative tool.

Depending on what happens where and under what conditions, the same feat might look quite different, even if the involved energy is mostly the same.

 

[Antvasima]

@Executor_N0 @Mr. Bambu @Therefir @TheRustyOne @Armorchompy @Migue79 @Psychomaster35 @KLOL506 @Dark-Carioca @AbaddonTheDisappointment @Aguywhodoesthings @DemiiPowa @Flashlight237 @SeijiSetto @SunDaGamer @Naito-desu @Floxy178 @ElJoaki5 @Drite77

Are any of you willing to help out here please?

 

[KLOL506]

Out of my realm of expertise I'm afraid.

 

[Antvasima]

No problem.

 

[Floxy178]

Eₖ = 9730 Joules

0.973 since velocity is in cm/s here.

So the assumption is that it's equal everywhere on surface and velocity drops linearly through depth? It seems fine to me mathematically, however I don't feel confident enough to comment on assumption, at least for now.

 

[Psychomaster35]

Funnily enough, I'm also trying to find a new formula for shaking feats as I have one particular feat in mind where a character crashes into a wall hard enough to cause the screen to shake which caused the cars in the background to jump. I know I could just get the KE of the cars, but since they ended up jumping despite being a distance away from the epicenter, I'm pretty sure the feat would be stronger than that, I just don't know what formula to use since these methods are starting to become invalid.

 

[Qurbonboev]

Bump

 

[Qurbonboev]

Bump

 

[Antvasima]

Do we have a sufficient staff consensus here to apply any revision based on this thread?

 

[Dalesean027]

Do we have a sufficient staff consensus here to apply any revision based on this thread?

I believe last we left off Agnaa was waiting on DT to word a better suggestion and though Vzearr provided his own solution, none of the CGMs who commented were able to judge if its the best replacement solution compared to anything else

 

[Antvasima]

@Executor_N0 @DontTalkDT @Ugarik

Are any of you willing to help out here please?

 

[Dalesean027]

Bump