|Date:||11/30/00 8:09:48 AM Pacific Standard Time|
the urls for the seismograms i sent you...
1230 - 1300 MST 23rd of November...1130 - 1145 & 1200 - 1230 MST 25th of
November...0351 - 0358 MST 29th of November...
have a period...peak to peak time duration...of about 20 seconds...
using the relationship f = 1/T that gives you a freqency of about 0.05
Hertz...a low frequency seismic event...
unlike a tectonic earthquakes which yield a frequency two orders
higher...about 5 Hertz...the low frequency events are associated with the
movement of magma...
these quotes are from USGS...
Harmonic Tremor: A continuous release of seismic energy typically associated
with the underground movement of magma. It contrasts distinctly with the
sudden release and rapid decrease of seismic energy associated with the more
common type of earthquake caused by slippage along a fault.
Volcanic tremor, a type of continuous, rhythmic ground shaking different
from the discrete sharp jolts characteristic of earthquakes. Such continuous
ground vibrations, commonly associated with eruptions at volcanoes in
Hawaii, Iceland, Japan, and elsewhere, are interpreted to reflect subsurface
movement of fluids, either gas or magma.
All Hawaiian eruptions are accompanied by harmonic tremor (also called
volcanic tremor). Quite distinct from the discrete seismic shocks associated
with rupture-caused earthquakes, harmonic tremor is a continuous vibration
of the ground caused by magma movement. Harmonic tremor generally is
detectable and recorded only by seismic instrumentation; however, if
especially vigorous, tremor can be felt by people as far as 5 miles from the
Yellowstone Caldera has been quiet for months...there appears to be magma
movement at 1230 - 1300 on the 23...and then there is the 4.3 tectonic quake
at 2120 on the 23...
but...none of the harmonic tremors are showing up on the REAL-TIME
and...the eq listings below the map are all jumbled up...
so...you tell me what's goin' on...
this reminds me of the "head-in-the-sand" attitude of the USGS every time
Long Valley Caldera acts up...