Starting / stopping an earthquake

[Juddog]

This is a question for the scientific-minded folk that I saw on another forum.

Hypothetically, would it take more force to start or to stop an earthquake?

Assume in each case that the earthquake being stopped / started was of equal magnitude, say for example a seismic magnitude 4 quake.

 

[JulesMaximus]

I would think it would take an equal amount of opposing force to stop a quake.

 

[Farmer]

If we would speak about energy instead, ideally the same, but since energy dissipates, it would take less energy to "stop" an earthquake as opposed to "starting" one, assuming the methods of "starting" and "stopping" are equally efficient.

 

[hanoverphist]

ask tesla

 

[Juddog]

I would think it would take an equal amount of opposing force to stop a quake.

This was my initial thought as well; assuming that both instances had an earthquake of the same magnitude, I thought it would be similar to sound waves (where to create an anti-noise, you generate a noise with the same amplitude but opposite phase).

 

[Farmer]

This was my initial thought as well; assuming that both instances had an earthquake of the same magnitude, I thought it would be similar to sound waves (where to create an anti-noise, you generate a noise with the same amplitude but opposite phase).

That's probably true. But earthquakes "sources" are random. If you build one "driver" and drive at a certain frequency, the phase will be different depending on where you go, you can't get perfect cancellation.

So there needs to be many drivers.

Pretty much, if you have a plate that can shake in a random fashion, in order to cancel the shake, you have to be able to drive all the harmonic modes. (That's actually pretty extreme, called "cancelling the plant," you can't really achieve that). You would have to control that plate very well.

Since earthquakes are also dynamic (i.e., time varying), you would need some kind of closed loop feedback on the drivers, the more accurate and faster responding the better.

Essentially a feedback control system, not too unlike a car's suspension system, except on an epic scale.

 

[SMOGZINN]

It would take a lot more energy to stop an earthquake in progress then to start one.

Earthquakes are caused by build up of pressure between tectonic plates. When the pressure gets high enough to overcome the friction between the plates they move, causing an earthquake. So, to cause an earthquake all you have to do is lower the friction between the plates, in some cases that would take very little. But once the plates start moving, it is a lot harder to cause enough friction to stop them. To stop one in progress you have to overcome the momentum of the plates to the point that friction takes back over. I can't even imagine how much energy that would take.

 

[lord_emperor]

I don't think there is any "stopping" to be done, quakes are the result of a plate moving suddenly, the resulting damage is from the shaking/shifting of the land around it afterwards.

An exactly inverted waveform pounded into the earth somehow could possibly cancel out the seismic waves in a given direction. It would take some neat engineering to detect and earthquake, calculate how to counter it and deploy whatever device in a useful location though.

Not to mention you'd have created an equally powerful seismic wave anyway and only really prevented damage exactly between the two epicentres.

 

[BoomerD]

I don't think there is any "stopping" to be done, quakes are the result of a plate moving suddenly, the resulting damage is from the shaking/shifting of the land around it afterwards.

An exactly inverted waveform pounded into the earth somehow could possibly cancel out the seismic waves in a given direction. It would take some neat engineering to detect and earthquake, calculate how to counter it and deploy whatever device in a useful location though.

Not to mention you'd have created an equally powerful seismic wave anyway and only really prevented damage exactly between the two epicentres.

So just lubricate the plate joint to reduce friction...let the plates slide quietly and without jolting...

Of course, there may be a bit of surface disruption since the plates will be covered by quite a bit of materials that may be somewhat interconnected...soil, roads & bridges, buildings, etc...

:biggrin:

 

[Leros]

So just lubricate the plate joint to reduce friction...let the plates slide quietly and without jolting...

Of course, there may be a bit of surface disruption since the plates will be covered by quite a bit of materials that may be somewhat interconnected...soil, roads & bridges, buildings, etc...

:biggrin:

The solution is always more lube.

 

[EagleKeeper]

The solution is always more lube.

And you expect Mother Nature to bend over and take it without a complaint.:wub:

 

[Locut0s]

MUCH less force would be required to start an earthquake. Assuming you are starting one along a fault line that already has a lot of stress built up. Stopping one just wouldn't be possible in real life. However if it were possible it would require a HUGE amount of energy as you are talking about stopping a large part of the crust from moving. You are talking about stopping billions of tons of rock from moving.