Hurricane Season & Microseisms
Microseisms are the dominant natural noise that we record on broad-band seismographs. This noise looks like continuous harmonic motion with varying patterns of amplitude modulation. The typical wave period of the harmonic motion is 6 seconds, though it can vary from 4 to 12 seconds.
Hurricane Bonnie: August 1998
Hurricane Georges: September 1998
- For Hurricane track information, go to:
National Hurricane Center, or
Hurricane arhcive at Purdue
Then compare to seismic data below:
"Typical" seismogram at AAMN (plot gain is x32) on Sept. 21 & 21 hr, with background noise before arrival of Hurricane Georges.
AAMN seismogram (plot gain is x32, same as above) around the peak amplitude in the microseism storm on Sept 25 & 9 hr.
Note that the dominant period of the microseism maximum is about 8 seconds (compare to Hurricane Bonnie).
But, even more puzzling is the location of Hurricane Georges during this microseism peak (look at track in the above Hurricane web sites).
AAMN seismogram (plot gain is x32, same as above) on Sept. 29 & 18 hr during the secondary peak in the 5 second microseisms.
Where is Hurricane Georges now?
Graph of the 5-second and 8-second microseism amplitudes at MichSeis station AAMN, just north of Ann Arbor, MI
This graph shows microseism amplitude over 11 days from Sept. 21 through October 1, 1998.
Click for technical details of analysis
- After you have compared the track of Hurricane Georges (available from the above Hurricane web sites) with the microseism amplitude data, you might still have some questions about the association of hurricanes and microseisms.
If so, you might be interested in this
image (courtesy of the US Navy) of ocean wave heights from Sept 25 & O hr.
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