. . . unless we're SLEEPING through Life and Time.
You never know. I like the idea of a reference back to the beginning of the thread. I'll adopt that.
MY MY MY -- Woudja lookee here.
No, fellas, this sort of widespread >HIT< doesn't happen very often.
[edit on 12-11-2004 by Emily_Cragg]
Here's more on how to read earthquake seisigraphs.
How to read "webicorder" images and seismograms:
"Webicorder" images digitally simulate seismograms recorded at the Earthquake Studies Office. Seismograms are records of ground motion at
seismograph stations in the Montana Seismograph Network made each 24-hour period. Seismograms are "read" like a book, from left to right, and then
from top to bottom (these are the directions on the images that time increases). As with a book, the right end of any horizontal line "connects"
with the left end of the line below it. The color of each horizontal line has no significance, but makes the "webicorder" image (seismogram) easier
The vertical lines are spaced at one-minute intervals. The time of day (Hours:Minutes) is indicated in the left margin in Mountain Daylight Time (On
the hours) and at the right margin in Universal Coordinated Time (Greenwich Time) (On the quarter-hours).
When a seismic event occurs, seismograms show ground motion at the location of the recording instrument that typically lasts from several tens of
seconds to many minutes, depending on the size of the event and its distance from the recorder. The height of the waves on the seismogram (wave
amplitude) is a greatly magnified representation of the actual ground motion. The magnification of some stations may be greater than 100,000 times. An
earthquake recorded on a seismogram has recognizable characteristics: Typically, you can see the arrival the Compressional Wave, P, (travels fastest
through the earth), and S, Shear Wave (somewhat slower).
On our seismograms you may see local earthquakes in Western Montana, regional earthquakes, from surrounding states and the Pacific Northwest, and
earthquakes elsewhere in the world having a magnitude greater than 5.5 on the Richter scale. For distant earthquakes be sure to look at the "broad
band" seismogram (BOZ). Broad band seismographs are equally sensitive to high frequency shaking from local earthquakes and to low-frequency ground
motions generated by distant earthquakes. The lower frequency surface waves generated by a distant earthquake will only be visible on broad band
Not all the waves on seismograms are caused by earthquakes. Anything that produces ground vibrations is recorded. For example: Vehicles on nearby
roads (why we try to locate our seismometers well away from roads), Wind noise and thunder, Animals passing nearby (a herd of elk for example).
Man-made mine blasts, such as the ones from: Montana Tunnels, Golden Sunlight, the Continental Pit, and Yellowstone Talc. The uniform amplitude ground
vibration at certain stations, (BZMT, STMT) is caused by nearby equipment.
Non ground motion signals that are common are: Pulses at regular intervals during daylight hours on some stations, (for example SLMT, BGMT) are caused
by the solar charging system voltage regulator. Radio noise: Since the seismic signals from the seismometers are typically transmitted to the
Earthquake Studies Office using low-power FM radio links, other radios with similar frequencies may interfere with our signal. Interference is usually
easy to distinguish from earthquakes because the the interference is often "spiky" or "one-sided", and begins and ends abruptly.
Webicorder Seismograms for regional Seismic Stations are available at:
UUSS Webicorder (Seismogram) Displays (Utah and Yellowstone National Park Seismic Networks).
WEBICORDERS - Real-time PNSN Seismograph displays (University of Washington Seismic Network).
24 Hour Seismic Data Plots (Canadian National Seismograph Network).
[edit on 12-11-2004 by Emily_Cragg]