PSN-L Email List Message

Subject: Shadow Zone Graphics
From: "Connie and Jim Lehman" lehmancj@...........
Date: Sun, 17 Dec 2006 20:10:57 -0500


PSN folks--for those of you interested  and have access to the Journal =
of Geoscience Education the November '06 issue has an article on: =
Techniques for Mapping Theoretical Shadow Zone for Direct P and S Waves =
Propagated as Rays from an Earthquake Epicenter.  One of the authors, =
Prof. Richard Kroll has done a splendid piece of work for the past 20 =
years with  amateur type long period sensors in a classroom setting at =
Kean Un. in New Jersey.  Any College or University  offering Geological =
courses would have this Journal around as it is the official publication =
of the National Associatioin of Geoscience Teachers.
http://www.nagt.org=20
   The shadow zone for any seismic sensor location is 103-143 degrees =
distant.  For us in Virginia, we get lots of shadow zone profiles as the =
"hot" South Pacific region falls  over those limits.  A wall mounted =
world map showing the shadow zone for your station location would make =
an nice addition for quick reference.
   Although Prof. Kroll did not include this feature,  a bold line about =
152 degrees would identify the locations where "seismic caustics" are =
noted in the signature.  Of course bagging a "caustic" is more rare, as =
the open window for the caustic profile must have the epicenter distance =
within a degree or so of 152 degrees.  A long period 'Caustic' profile =
shows the first waveforms arriving to be greater or equal in amplitude  =
than found elsewhere in the record. =20
    Season's Greetings to All                          Jim Lehman

=20
=20







PSN folks--for those of you=20 interested  and have access to the Journal of Geoscience = Education=20 the November '06 issue has an article on: Techniques for = Mapping=20 Theoretical Shadow Zone for Direct P and S Waves Propagated as Rays from = an=20 Earthquake Epicenter.  One of the authors, Prof. Richard Kroll = has=20 done a splendid piece of work for the past 20 = years with =20 amateur type long period sensors in a classroom setting at Kean Un. in = New=20 Jersey.  Any College or University  offering Geological = courses would=20 have this Journal around as it is the official publication of the = National=20 Associatioin of Geoscience Teachers.
http://www.nagt.org =
   The shadow = zone for any=20 seismic sensor location is 103-143 degrees distant.  For us in = Virginia, we=20 get lots of shadow zone profiles as the "hot" South Pacific region=20 falls  over those limits.  A wall mounted world map showing = the=20 shadow zone for your station location would make an nice = addition for=20 quick reference.
   Although Prof. = Kroll did not=20 include this feature,  a bold line about 152 degrees would identify = the=20 locations where "seismic caustics" are noted in the signature.  Of = course=20 bagging a "caustic" is more rare, as the open window for the caustic = profile=20 must have the epicenter distance within a degree or so of 152=20 degrees.  A long period 'Caustic' profile shows the first waveforms = arriving to be greater or equal in amplitude  than found=20 elsewhere in the record. 
    Season's = Greetings to=20 All           &nbs= p;            = ; =20 Jim Lehman
 
 
 

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