## PSN-L Email List Message

Subject: Re: P-waves
From: Christopher Chapman chrisatupw@.......
Date: Fri, 25 Mar 2011 10:10:20 -0400 (EDT)

```

Subject: Re:P-waves

Found what I was looking for ,,,,,  a animation of a P wave
http://www.geo.mtu.edu/UPSeis/images/P-wave_animation.gif

notice there is NO vertical motion, it is totally longitudinal
P waves travel like sound waves do  :)

=20
Hi Dave,
=20
Oops ! P waves are of course longitudinal compression waves, BUT :-
=20
Now  turn the animation at quite a sharp angle to the vertical to obser=
ve a =20
real P wave and you get quite a strong vertical component! If you observe a=
local=20
quake directly under you, you will ONLY see a vertical component!=20
Being body waves, P and S waves are usually refracted upwards as they n=
ear=20
the surface of the Earth, steepening the angle of approach. .

Regards,

Chris

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

=20

Am I correct in assuming that your clocks use a vertical pendulum with a=
period between 1 and 2 seconds?=20
Bryan Mumford

=
Subject: Re:P-waves

Found what I was looking for ,,,,,  a animation of a P wave
http://www.geo.mtu.edu/UPSeis/images/P-wave_animation.gif

notice there is NO vertical motion, it is totally longitudinal
P waves travel like sound waves do  :)

Hi Dave,

Oops ! P waves are of course longitudinal compressi=
on waves, BUT :-

Now  turn the animation at quite a sharp angle=
to the vertical to observe a

real P wave and you get quite a strong vertical component! If you obse=
rve a local

quake directly under you, you will ONLY see a vertical component!

Being body waves, P and S waves are usually refract=
ed upwards as they near

the surface of the Earth, steepening the angle of approach. .

Regards,=

Chris

Am I correct =
in assuming that your clocks use a vertical pendulum with a period between =
1 and 2 seconds?
Bryan Mumford

```