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.
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