PSN--thanks for the Iris Waveform Chart for the 9.0 Sumatra  12/26/04 =
event.  The surface wave arrivals of multiple stations exhibited by =
distance, and text,  makes a super graphic.  I was wondering about  the =
occurrence of a seismic caustic at the appropriate degree distance.  Was =
the gap at 160 degree area due to no reporting station near the =
"caustic" distance.  In periodic recording here we've copied three =
caustics  in 20 years--I believe the events were southwest of Australia =
for us--not a very hot spot.
    The 18 sec long period system at James Madison Un.  (Virginia) =
working into a graphic readout read the 8.1 Macquarie Is. event-(l2/23) =
nicely, but the 9.0 event read 20 min after P-diff arrived and then went =
off scale for 100 minutes and returned to normal recording for the 7.1 =
event at 04:21.  One can conclude, surface wave arrivals for us (at =
approx. 145 degrees) were obscured.  Keep up the good work.
            Jim Lehman







PSN--thanks for the Iris Waveform Chart =
for the=20
9.0 Sumatra  12/26/04 event.  The surface wave arrivals of =
multiple=20
stations exhibited by distance, and text,  makes a super =
graphic.  I=20
was wondering about  the occurrence of a seismic caustic at the =
appropriate=20
degree distance.  Was the gap at 160 degree area due to no =
reporting=20
station near the "caustic" distance.  In periodic recording here =
we've=20
copied three caustics  in 20 years--I believe the events were =
southwest of=20
Australia for us--not a very hot spot.
    The 18 sec long =
period system=20
at James Madison Un.  (Virginia) working into a graphic readout =
read the=20
8.1 Macquarie Is. event-(l2/23) nicely, but the 9.0 event read 20 min =
after=20
P-diff arrived and then went off scale for 100 minutes and returned to =
normal=20
recording for the 7.1 event at 04:21.  One can conclude, =
surface wave=20
arrivals for us (at approx. 145 degrees) were obscured.  =
Keep up=20
the good work.
          =
 =20
Jim Lehman