Hi All. Here in part is the latest on the “slow quake” in Washington State. It appears the slow quake has changed, or is in the process of changing. As to what it means no one can really say with any degree of certainty. Sort of waiting for the other shoe to drop. Take Care…Don in creepy town

May 22, 2004 - We are worried. The tremor seems to have almost completely stopped. There is no doubt that there was an ETS event located in the south Puget Sound area centered around the time May 2-14 based on strong tremor and now the reported GPS measurements show a very significant event,.... but only in the south. Nothing has moved to the north where our arrays are located. We are waiting and waiting........

May 17, 2004 - The deep tremor seems to be at MUCH lower levels for the past 4 days. It may be spreading slightly north and south. There is some indication that we are seeing it as far south as near Portland, OR. However, it is so weak that it is difficult to see on more than a few stations some of the time.

May 15, 2004 - Over the past 36 hours the strong tremor has died out. There are still weak periods of tremor in the south Sound area but not periods of strong tremor anywhere.

May 14, 2004 - Processing of GPS data (courtesy of Dan Johnson) shows geodetic changes at stations in southern Puget sound over the last few days. See GPS measurements of 2004 tremor

May 13, 2004 - Tremor continues in south Puget Sound area but seems to have moved somewhat farther north over the past couple of days. Some particularly strong tremor bursts can be weakly seen on sensitive stations in the north. There is an example spectrogram from a station in the west central Puget Sound (HDW) for last night which shows a very strong tremor burst at about 01:50 PDT.
Telemetry connections have been established to four stations in the Lopez array (Thanks Lopez School for the help!), and we can now down-load waveform segments from these stations in near realtime, but are not trying to do true real-time telemetry. Two stations from the Sooke array are being telemetered to the PGC where they are recorded but not being transfered to us yet.

May 10, 2004 - I think we can say that the slip event has started!! It is still concentrated in the southern Puget Sound, but there is evidence that it is moving north. It is certainly getting stronger and more near continuous and thus being recorded on stations in the central and on quiet stations in the north. Thus far we don't think it would be recorded on any of the array stations that are too far north. Example Spectrograms from earlier today illustrate how the tremor changes with time and that it is strongest in the south Sound. Actually station HDW is very quiet and sensitive so it exagerates the tremor strength there.

May 7, 2004 - Not much change in tremor today. There continue to be relatively small bursts from time to time but only in the south-of-the-Sound area. Locations could be determined for several burst and are shown on a Tremor Burst Map as red stars. Blue triangles are possible stations used for detecting and/or location.
May 6, 2004 - The burst of tremor south of Puget Sound are continuing off and on over the past couple of days. There are periods of 6 or more hours without anything obvious and then there will be several hours with at least 10 minutes of low-level tremor. This morning, May 6 at about 1405Z an extended period (~45min) of fairly strong tremor took place which was well recorded on all south Sound stations and weakly at stations to the north and east. Most tremor bursts are being seen only stations south of the central Puget Sound.

May 4, 2004 - Again we have seen some bursts of deep tremor from the area south of Puget Sound during May 3-4, but no bursts last more than 20-30 minutes and nothing seems to be north of there. When is it going to really start?
Apr. 27, 2004 - A few short period of weak tremor were seen today on stations to the south of Puget Sound. The location seems to be near Centralia. This is the first time that deep tremor has been clearly seen south of Olympia.

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