IRIS EPO

For educators, college/university faculty and professionals interested in the instruction of seismological concepts in primary and secondary classrooms.

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Active Message Threads for May 2007

John or Jan Lahr
2007-05-03 16:25:27 - 2007-05-03 22:33:57
Hi Chris, Good questions. For the helicorder view AmaSeis only allows one filter to filter out high frequencies and one to filter out low frequencies. For example, if you want to enhance the high frequency signals from local events on your helicorder record, you might filter out frequencies below 1.5 Hz, which leaves frequencies between 1.5 Hz and 3 Hz. (Note that because we are only sampling at 6 Hz, the highest frequency that can be resolved is 3 Hz.) The bottom of the helicorder ... [more]
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John or Jan Lahr
2007-05-03 06:30:09 - 2007-05-03 15:37:20
A while back I showed how to set up a helicorder filter in AmaSeis so that the surface waves from distant earthquakes would be enhanced. (See: http://jclahr.com/science/psn/as1/filtering/index.html) The other day I received an earthquake notification message* from the USGS about a 3.1 earthquake not too far from my station in Corvallis, Oregon. Although I couldn't see anything on my helicorder record, especially with the filter I was using to enhance low frequencies, by switching to a... [more]
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