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<DIV><FONT face=Arial size=2>Hello,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I face some problem when applying the
command "interpolate delta XX" in some noise data. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I have some 1-hour noise data
recorded in CMG-5 guralp sensors and I want to interpolate them for further
processing in SAC software. The raw *.cgf files (the format of
the CMG-5 sensors) have already transformed to *.sac files through Scream
V4.4 software provided by Guralp.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The *.sac data (un-interpolated data) have
delta 0.01sec and I want to interpolate them to delta 0.05sec. </FONT><FONT
face=Arial size=2>I use the following commands in my SAC 8/8/2001 V. 00.59.44
(Copyright 1995) software which runs in Fedora 9.0:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>r *.sac</FONT></DIV>
<DIV><FONT face=Arial size=2>qdp off</FONT></DIV>
<DIV><FONT face=Arial size=2>rmean</FONT></DIV>
<DIV><FONT face=Arial size=2>rtrend</FONT></DIV>
<DIV><FONT face=Arial size=2>p1</FONT></DIV>
<DIV><FONT face=Arial size=2>interpolate delta 0.05</FONT></DIV>
<DIV><FONT face=Arial size=2>w change .sac .inter</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>When I plot the un-interpolated (*.sac) and
interpolated data (*.inter) to see if the interpolation works ok (Fig. 1 in the
attach file) the result seems ok, but when I zoom in different time
windows the result is not at all good! Specific spikes in my
un-interpolated noise data seem to "move" in time in the </FONT><FONT
face=Arial size=2>interpolated data as you can see in the attach doc
file. This "moving" seems to happen after some time (e.g. in fig. 2 the
coincidence of specific spikes between un-interpolated and
interpolated data is very good, but this does not happen for the rest time
windows,fig. 3-5).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I cannot understand why this
happen.</FONT></DIV>
<DIV><FONT face=Arial size=2>If someone has faced this problem again and have
any idea, please let me know.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Best Regards,</FONT></DIV>
<DIV><FONT face=Arial size=2>maria manakou</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
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