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Science Forum Index » Geology - Earthquakes Forum » Waveform question
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| Charles |
 Posted: Sun Mar 18, 2007 1:18 am |
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| Guest |
| Posted: Sun Mar 18, 2007 1:44 am |
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In article <uampv2h70v2gen0cff8daafpnlssassg3n@4ax.com>,
Charles <ckraft@SPAMTRAP.west.net> wrote:
Quote: What causes the sinusoidal pattern in the
baseline of several of the traces?
It wouldn't happen to be 60Hz would it? |
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| Charles |
| Posted: Sun Mar 18, 2007 1:48 am |
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On Sun, 18 Mar 2007 06:44:15 -0000, ellis@no.spam () wrote:
Quote: In article <uampv2h70v2gen0cff8daafpnlssassg3n@4ax.com>,
Charles <ckraft@SPAMTRAP.west.net> wrote:
What causes the sinusoidal pattern in the
baseline of several of the traces?
It wouldn't happen to be 60Hz would it?
About nine cycles in 120 seconds.. |
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| Bob Eld |
| Posted: Sun Mar 18, 2007 10:38 am |
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"Charles" <ckraft@SPAMTRAP.west.net> wrote in message
news:uampv2h70v2gen0cff8daafpnlssassg3n@4ax.com...
It looks like about 0.16Hz or six or seven seconds per cycle. Is that what
you see? This is more of a question than an answer but could it be the
fundamental resonance of the seismograph being excited by the quake? If so,
it is an artifact of the instrument and not a part of the earth's motion.
Seismographs like all transducers, loudspeakers, etc. have resonances due to
their very nature of having mass and compliance. These resonances must be
carefully damped or the resulting waveforms will not be an accurate
reproduction of the original form. We've all heard "boom box" speakers where
this problem occurs in a poorly designed speaker. An improperly damped
seismograph could exhibit the same problem. |
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| rick++ |
| Posted: Sun Mar 18, 2007 11:15 am |
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Six second noise can be common.
I've heard peopel attributed to breaking ocean waves. |
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