PSN-L Email List Message

Subject: Re: P-waves
From: Geoffrey gmvoeth@...........
Date: Tue, 29 Mar 2011 22:10:34 +0000


Hello yous guys:
how about some philistinian philosophy.
If it works like sound waves in the ocean
you get convergence zones where the sound
bends upward to the slower velocity
then reflects downward from the surface interface
and simply repeats in an expanding ring,
until the energy dies away by whatever causes
the losses like spreading or heat or whatever
else is included in the concept of ENTROPY.
ENTROPY to me is the seeking of equilibrium
in a universe which has little damping effect.
Not just the law as stated in Thermo-Dynamics.
All forms of energy end up as the 3d kelvin background.
Convergence zones within the ocean only work in
very deep waters with the correct temperature gradient.
The ocean is (I imagine) much purer and more homogenous
(well mixed) than is the earths rock.

IN 26 billion years ABB it will be 1.5d K
in 52 billion years 0.75
in 104billion 1/2 that. usw...
Trying to make order out of the universe simply
makes the losses happen faster.
We gotta start looking at universal time
in solar lifetimes and not atto-seconds.

Like, it takes 2 pounds of coal/oil/gas
to make the same amount of electricity
as the energy in a single pound of whatever.
Half the energy is lost just getting it to your homes.

I sort of laugh at these Quantum Physics peoples who
do not know what is accelerating the "UNIVERSAL EXPANSION",
all I have to think is the three degrees of temperature expanding in a no
degree universe to see where the expansion is coming from.
As long as there is any temperature at all, we are doomed
to accelerated expansion. In a great "nothing, nothing" universe.
If there were a skin around the universe it would stop like
so much hot air in a balloon. But, it does not seem to be that way.
More vacuum than a vacuum, that’s what we seems to be with-out.
People like US are the only people giving meaning to the Universe.
Without thinking creatures, Any Universe at all, may as well not exist.
It would have no meaning at all.
Amateur Seismology, hoorah !.
As far as we know, humans are the only creatures
which give meaning to the universe.

Regards,
geoff


-----Original Message----- 
From: Mike Price
Sent: Friday, March 25, 2011 9:41 PM
To: psnlist@..............
Subject: Re: P-waves

P-wave velocity increases with depth. This causes the wave paths to not
be linear (and the wavefront is not spherical). The paths can be
visualized as upward curving concave arcs. P-wave motion is therefore
predominantly vertical when it reaches the surface at all distances from
the epicenter.

Mike

On 3/25/2011 9:30 AM, Brett Nordgren wrote:
> Bob,
>
> I quite agree with your analysis. Some transverse motion would happen
> with an acoustic wave travelling down a steel rod, for example, but that
> assumes a free surface, which isn't the case inside the earth. The fact
> that the formula for the P-wave velocity uses the bulk modulus of the
> earth's material rather than its elastic modulus pretty well proves your
> case.
>
> However it is still true that P-waves will have a substantial vertical
> component, arising from the fact that the wave front will always to some
> degree be coming up from under the station.
>
> Thanks,
>
> Brett
>
> At 11:42 AM 3/25/2011, you wrote:
>> I disagree with your hypothesis. Transverse motion is only possible
>> with a wave of finite cross-section. A P wave has a more-or-spherical
>> wavefront and is not a beam of sound. Even a beamed wave would have no
>> transverse motion at its center axis.
>>
>> Bob
>>
>> On Thu, Mar 24, 2011 at 5:17 PM, Brett Nordgren
>> <brett3nt@.............> wrote:
>> Dave,
>>
>> I think in real world seismology, not everything always exactly
>> follows the simple theory. We see P waves quite well on our verticals.
>> For one thing they are body waves and commonly approach the station
>> from an angle below the horizontal. Also I think there is always a
>> transverse motion associated with compression waves like P waves--look
>> up Poisson's Ratio. I would normally expect them to have a transverse
>> motion of very roughly 1/3 the amplitude of their longitudinal motion.
>>
>> Regards,
>> Brett
>
>
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