Re: No stiffness effect?

[brian whatcott <inet@INTELLISYS.NET>]

At 17:38 2/7/00 -0500, Ludwik wrote:
> ... experiments
> showed that the measured speed (via single pulse and via
> standing waves) was 12% (+/- 5%) higher than what was
> expected on the basis v=sqr(T/mu)=sqr(15/0.086) which
> leads to 13.2 m/s (+/- 3%)....
> Ludwik Kowalski

Students destined for Earth science might find this experiment useful.
Perhaps as a metaphor for seismic waves, where primary (or pressure)
waves are modeled as propagating at a speed of
sqrt[(k + 4/3*mu)/rho]
         k is the bulk modulus, indicating the degree of incopressibility
         mu the shear modulus, indicating the degree of rigidity
         rho the mass density

...and secondary (shake) waves are modeled to propagate at a slower
sqrt[mu/rho]

 From this basis, researchers were able to draw surprising conclusions
about a fluid core layer which could not sustain shake waves,
using impulsive excitation from earthquakes as a probe.

  I can speculate that students familiar with this theory would not
find it a long stretch to imagining the possibility of impulsive
low power radar.

(which reminds me that the Lawrence Livermore has recently succeeded
in reversing an earlier Patent Office decision to disallow
numbers of its patent applications for Micropower Impulse Radar -
 an invention contested by at least one small company in the field.)

If one can define a liquid core from the absence of shake waves -
one might consider next, surface waves of such long wavelength that the
ocean can be treated as shallow.  In this case, the long low-swelling
 sea wave radiating from the quake is the probe, allowing imaginative
investigators to estimate an ocean depth, using the relation for
'shallow' water, where the transmission speed of long surface waves
is given by
sqrt(gD)
            g is gravitational acceleration.
            D is ocean depth

It need a value for D = 4000 meters and g = 9.81 m/s^2 to arrive
 at the peppy 200 meters/second (450mph) wave speed from a quake.

The wave amplitude of perhaps 60 cm. is all but invisible in the
ocean swell  ...until D collapses, c shrinks, and wave heights
 swell to their ultimate tsunami form, onshore.

(ref: various Seismology articles in Enc Brit 15th Ed)




brian whatcott <inet@intellisys.net>
Altus OK