🚀 go-pugleaf

In article <2iv6lq$huj@crl.crl.com>, William H. Rowan <rowan@crl.com> wrote:
>My understanding of it is that there are two types of waves: the P (pressure)
>wave, which propagates by compression like sound waves, and the S (shear)
>wave, which propagates by side-to-side motion, like waves in a fence when
>you wiggle it.  The P wave travels faster than the S wave.  My memory of the
>P wave in a quake in 1977 was as a sudden bang, after which there were some
>seconds of quietness, and then the shaking started.  That was the S waves,
>which of course cause the destruction and bring buildings down.  This quake
>was a magnitude 4.5, I think, about 10 miles away.

There are many more than that, including those that propagate along interfaces
in rock.  P and S propagate through the interior of bodies.  Two interface modes-
called surface waves because they propgate at the rock-air interface- can have
higher amplitudes than P and S waves and cause destruction.  At short distances
the S and surface waves are scrunched together and that is what people feel.
At medium distances, people experience the surface waves as strongest.