Ben,
You wrote:
You wrote:
...I believe that a really large angled impact would transfer this energy in a pulse (not just a wave) through the hydraulic system that is the liquid mantle of the Earth....
Saturday, May 4, 2013
Re: [Geology2] Re: The Earth Moved
1. The mantle is not liquid, not even close.
2. A pulse is technically a wave, or more properly a superposition of many waves. Each frequency will have a different speed inside the Earth, and each will be refracted by a different amount. The medium is dispersive. Thus, the energy of a sharp impulse is broadly spread out, both in space and in timing. What you actually detect over the opposite hemisphere is an interference pattern that takes much longer to record than the initial pulse.
3. Since propagation speeds increase with depth, both in the mantle and core (liquid and solid parts), each layer acts as a sharply divergent lens, further spreading the energy of a localized impulse and creating large shadow regions where no wave reaches at all. In the case of the transverse component (S waves), the opposite hemisphere is nearly completely shadowed by the liquid core. All of the S energy is directed elsewhere or dispersed in the liquid core. For the longitudinal component (P waves), only a very diluted and unfocussed amplitude will reach the opposite node. What had started out in a one degree "beam" of vibration will be spread over a region the size of a continent.
4. Since long distance transmission will transform a pulse into a series of vibration modes, there is no net force for uplift. Instead, the fraction of energy that persists will just create alternating up and down motion. This is why distant seismometers tend to record oscillations rather than pegging to one side, even when the source was a sudden displacement in one direction.
Chuck
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