Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: EvaH on 30/03/2021 17:05:56

Douglas wants to know:
Does the energy released from an earthquake follow the Inverse Square Rule (or something similar) in relation to distance from the epicentre?
What do you think?

Does the energy released from an earthquake follow the Inverse Square Rule
The Inverse Square Rule applies to energy radiated equally in all directions in a 3dimesnional volume, from a point source.
Most Earthquakes consist of a slip along a fault line, so the source is 2dimensional, rather than a point.
 And the earthquake waves don't radiate equally in all directions.
 But if the Earthquake is far away (so it looks like a point from where you are), the strength of the earthquake shock does reduce with distance.
There are some special cases:
 If your home is built on loose and/or wet sediment, this can accentuate shaking and cause more damage to buildings, or liquify and swallow buildings.
 If you are located diametrically opposite the earthquake location on the Earth, the liquid core absorbs the "sideways" earthquake waves, leaving a bit of a shadow on the other side.
 Much of the damage from Earthquakes comes from Tsunamis. Because the ocean is a thin 2dimensional skin on the Earth, the Earthquake energy spreads out like 1/distance, not like 1/distance^{2}. This means that tsunamis can spread disaster further than the earthquake waves.

Hello Douglas!
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Evan has pretty much Explained it All!
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But if you wish to know a bit more about Seismic Waves, here's a Link which might be a good read.
https://www.britannica.com/science/seismicwave
P.S.  It would be Wise to know what category of Risk your locality falls under, there are separate earthquake prone zones categorised according to risk levels.
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Also just a simple rehearsal of the Act with your whole family & pets would Really help if it ever strikes.
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Tc!