Tremor examples from different ETS events
Return to main tremor page.
The following four spectrograms are examples from four different stations for
a single 12 hour period from the 2004 ETS.
Special Pages for complete ETS events at station, HDW
Station HDW, located on the edge of the Olympic Peninsula, is particularlly sensitive
to deep tremor in the south and central Puget Sound area. Looking at
spectrograms for this station over the course of an ETS event easily
illustrates the variability in time of the tremor and its frequency
content. For the most part tremor frequency is spread between 2-6 Hz with the
strongest tremor at about 4Hz and is somewhat bursty over time.
However, during the Winter-2008 ETS there was an unusual period of several days
(May 17-20) when the tremor seems to be even more continuous than usual and
within more individual frequency bands that vary slightly over hours.