IRIS EPO

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Active Message Threads for December 2006

ChrisAtUpw@aol.com
Dec. 31, 2006, 11:52 a.m.
In a message dated 31/12/2006, jerdell@cox.net writes: Greetings, I am trying to understand the band pass filters and have a few questions. 1. John Lahr stated that; “Since the AS-1 samples the amplitude of the seismic signal about 6 times per second, clearly high frequencies will not be well represented. The highest frequency that it's theoretically possible to record faithfully is one half of the sample rate.” You interpret this as six/2 = max frequency = 3Hz You tend not... [more]
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jerdell@cox.net
Dec. 30, 2006, 9:22 p.m. - Dec. 31, 2006, 10:57 a.m.
Greetings, I am trying to understand the band pass filters and have a few questions. 1. John Lahr stated that; "Since the AS-1 samples the amplitude of the seismic signal about 6 times per second, clearly high frequencies will not be well represented. The highest frequency that it's theoretically possible to record faithfully is one half of the sample rate." So if a sample is taken every .17 seconds (6 times per second) and you divide that in half you get .33seconds. Therefore seism... [more]
Replies
jerdell@cox.net
Dec. 30, 2006, 4:40 p.m.
Greetings and Happy New Year, I just wanted to share with everyone a problem I had with my AS-1 and the solution. I left for China on Aug 10th and as soon as I got to Chengdu and checked the school seismograph; http://www.pcds.org/share/earthquake/ it had stopped working. The seismograph was not recording anything; it was if the seismometer was no longer connected to the CPU. The next day I checked back and it was recording but the trace was wandering across the screen like a chicken in... [more]
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Alan Jones
Dec. 14, 2006, 5:45 p.m.
Neat story on sounds of the entire earth speeded up so you can hear them. Check out: http://www.npr.org/templates/story/story.php?storyId=6615446 Alan
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John or Jan Lahr
Dec. 2, 2006, 2:59 p.m.
Below is an excerpt from December newsletter of the Windows to the Universe program. http://www.windows.ucar.edu/ Second Anniversary of South-East Asian Tsunami by <http://www.windows.ucar.edu/tour/link=/bio/Roberta.html>Roberta December 26th brings the second anniversary of the <http://www.windows.ucar.edu/tour/link=/headline_universe/earth_science/stories_2004/tsunami_news.html>massive tsunami in 2004 which brought destruction and death to many countries bordering the Indian Ocean... [more]
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