HDW Spectrograms for winter 2008 ETS event

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.


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