[Siegfried]

Here's a seismograph from Mt Rainier showing the arrival at just before 0110 UTC

http://www.pnsn.org/WEBICORDER/VOLC/LO2_SHZ_UW.2004122600.html

Interesting that the pen was swaying up and down in a long period cycle for at least ten minutes before the vibrations started. I wonder if that was caused by longer wavelengths traveling faster through the earth? Maybe a more direct route?

[Strategerist]

Interesting that the pen was swaying up and down in a long period cycle for at least ten minutes before the vibrations started. I wonder if that was caused by longer wavelengths traveling faster through the earth? Maybe a more direct route?

That's how earthquakes are located. The various types of waves travel at different speeds. Once you figure out the time difference, you can figure out how far away from a given seismometer a quake was, and draw a circle with that radius. If you have three seismographs in widely different places, if you draw three circles, the circles will cross in one place..and that's where the earthquake was located.

[COEXERJ145]

I wonder if that was caused by longer wavelengths traveling faster through the earth?

Most likely. Certain seismic waves travel faster than others.

[Strategerist]

Incedentally that's how you can get screwy quake sizes and locations from these local guys in these countries; their seismographs have trouble showing the wave types of huge quakes because they're so close to the quake the whole seismograph is a confused, saturated mess, and their seismographs aren't very far apart from each other so you don't get a good accurate location. Because NEIC is worldwide, ironically, you get better info from instruments FURTHER from the earthquake if it's a huge quake.