PSN-L Email List Message
Subject: Fwd: Re: Iris Waveform Chart
From: John or Jan Lahr johnjan@........
Date: Sun, 06 Feb 2005 22:06:35 -0800
John Taber, below, points out two sources of information on caustics that
are on the web.
The upper set if figures on Paul Richards's page (second URL below) shows
how caustics can develop when even when the velocity increases
continuously with depth.
The lower set of figures shows how a shadow zone and caustic are created
when there is a low velocity zone.
Date: Sun, 6 Feb 2005 22:17:39
Subject: Re: Iris Waveform Chart
To: John or Jan Lahr <johnjan@........>
From: John Taber <taber@........>
That is my understanding as well. It is a point
where energy will be focused. Rick Aster has a fairly complete
.. One website which shows an example, but without defining it is
I had unsubscribed from the PSN list while I was away so your email
reminded me to resubscribe.
On Sunday, February 6, 2005, at 08:13 PM, John or Jan Lahr wrote:
My understanding is that a caustic is formed when the derivative of
Take-off angle is zero. ("Distance" is the angular
distance from the earthquake
to the place where the ray reaches the surface of the Earth and Take-off
measures the direction with respect to vertical that the ray leaves the
Other cases of constructive interference are not termed caustics as far
know. I'm traveling now, so can't refer to any seismology books and
yet to find a good explanation on a web site.
Maybe John Taber or Alan Jones can double check me on this!
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