Hi Gary, if you would like to see the shadow zone for a given quake, 
here is a little process of links.  Start at the 7 day USGS link...  
when you get there, scroll and click on the M5+Earthquake list link:

http://earthquake.usgs.gov/eqcenter/recenteqsww/

Click on the date / time link...  (example link for the 7.2)

http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2009cybb.php

Click on the Scientific & Technical TAB which takes you to the following 
link:

http://neic.usgs.gov/neis/eq_depot/2009/eq_090211_cybb/neic_cybb_t.html  

Scroll down and click on the  Theoretical P-Wave Travel Times link, 
where you will see a map that shows the approx shadow zone region 
(outlined by bold black circles), and a short explanation.

A Google for surface waves will provide lots of links...  here is a link 
to a short simple explination that I found helpful:

http://www.uwm.edu/~bketter/Research/Surface_Theory/Surface.html

If you happen to be in the area of the heavy red lines (several red 
lines bunched together), on the other side of the shadow zone, you can 
sometimes get reinforced signals that will surprise you on how big the 
trace is for what you would expect for otherwise smaller quakes.
  
  Enjoy, Stephen
  PSN Station #55


Gary Lindgren wrote:
> Hi Ted,
> I'm in Palo Alto CA. Tell me more about the shadow zone. I guess you saw
> what I saw. The ringing went on for a hour or so.
> Gary
>   



  
  


Hi Gary, if you would like to see the
shadow zone for a given quake, here is a little process of links. 
Start at the 7 day USGS link...  when you get there, scroll and click
on the M5+Earthquake list link:



http://earthquake.usgs.gov/eqcenter/recenteqsww/



Click on the date / time link...  (example link for the 7.2)



http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2009cybb.php



Click on the Scientific & Technical TAB which takes you to the
following link:



http://neic.usgs.gov/neis/eq_depot/2009/eq_090211_cybb/neic_cybb_t.html  




Scroll down and click on the  Theoretical P-Wave Travel Times link,
where you will see a map that shows the approx shadow zone region
(outlined by bold black circles), and a short explanation. 



A Google for surface waves will provide lots of links...  here is a
link to a short simple explination that I found helpful:



http://www.uwm.edu/~bketter/Research/Surface_Theory/Surface.html



If you happen to be in the area of the heavy red lines (several red
lines bunched together), on the other side of the shadow zone, you can
sometimes get reinforced signals that will surprise you on how big the
trace is for what you would expect for otherwise smaller quakes.

   

  Enjoy, Stephen

  PSN Station #55





Gary Lindgren wrote:

  
Hi Ted,
I'm in Palo Alto CA. Tell me more about the shadow zone. I guess you saw
what I saw. The ringing went on for a hour or so.
Gary