🚀 go-pugleaf

In article <1994Jan26.184923.4533@TorreyPinesCA.ncr.com> Max Stern,
lms@TorreyPinesCA.ncr.com writes:
>This accords with and explains my own personal experience.  I live in
>Sherman Oaks, and it happened that I was on the phone with people as
>far as ten miles away during several of the larger aftershocks.  Within
>a fraction of a second, we both announced that we were experiencing an
>aftershock.  At first, I thought this was incredible, since the wave
>has to take finite travel time, and I was thinking in terms of the
>speed of sound.  Then I read an article in the paper which cited the
>very high speed of the S wave, which -- together with Richard's point
>about "phase velocity" of the spherical wavefront's intersection with
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I think that this should be the "group velocity".  No energy or
information moves at the phase velocity.

>the surface -- makes the near simultaneity of its arrival at distant
>points quite understandable.
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Robert Jensen
jensen@aplcomm.jhuapl.edu