...... PNSN ETS HISTORICAL RECORD

This page will have frequent updates from observations and studies of Cascadia deep tremor expected during the fall of 2006. CAFE has several different goals including imaging the structure of the Cascadia subduction zone and a study of deep tremor associated with Episodic Tremor and Slip (ETS).
News will be posted on this page (latest at the top) and references to figures from time to time.

Map of CAFE stations in operation as of Oct 10, 2006

NEWS (latest at the top)

• Feb 10, 2007 - LAST NEWS REPORT FOR THIS ETS. Since nothing has been seen in past week it is declared to be over. Service runs to collect data from the CAFE stations will take place during the last part of this month.
• Feb 5, 2007 - It seems it really is over. We have seen no more tremor in Washington and the PGC reports no tremor in Canada. It seems that it suddenly stop on Feb 2. The last tremor envelop plot shows the winding down of signals common to the northern stations.
• Feb 3, 2007 - John Cassidy of the PGC reports that tremor on Vancouver Island seems to have stopped sometime yesterday. The last tremor clearly seen coming from the north on PNSN stations was early on Feb 2 and from the southern Puget Sound was weak tremor early on Feb 1. Is this ETS over?
• Jeb 1, 2007 - The Pacific Geoscience Centre released an official Press Release today about the ETS event arriving in Canada. Our Tremor Location Map now has tremor burst timing color coded by day of the month in January, 2007. It can be compared to the CAFE Station Map at the same scale.
• Jan 31, 2007 - The main tremor activity that started in the Puget Sound region two weeks ago has moved north of the Olympic Peninsula and is now in Canada. Canadian seismic displays can be used to track it northward. Also, Honn Kao of PGC is runing a Tremor Activity Monitoring System (TAMS) that can plot the stations with tremor each hour. He can make these available daily e-mails if you leave a message for Dr. H. Kao at Earthquake Canada's Web site at http://earthquakescanada.nrcan.gc.ca/comments_e.php.
  In the past few days minor bursts of tremor have been detected again in the southern Puget Sound area. Either this is residual tremor or perhaps new activity now moving south. Also, Herb Dragert of PGC has provided plots of selected GPS stations that clearly show the ETS displacements of stations in the southern Puget Sound region starting a couple of weeks ago and perhaps slowing down or stopping in the past couple of days. The PGC provides ETS Event Monitor Web pages that includes updated GPS plots. Preliminary processing of two PBO strainmeter are provided by Evelyn Roeloffs of the USGS for Southern Puget Sound (B018) and for northwest Olympic Peninsula (B004). Each shows transients associated with the ETS.
• Jan 29, 2007 - Over the weekend it appears that, at least some of the main tremor bursts moved offshore of the northern Olympic Peninsula and crossing the Straights. While tremor is still being recorded on stations in the central Puget Sound, most of it seems to be coming from the north. Tim Melbourne of CSU has provided raw tiltmeter records for the past several months from a long baselength tiltmeter near Shelton, WA. He reports that the transition in tilt seen around Jan 14-16 is likely associated with the ETS event.
• Jan 26, 2007 - Its definitely on the move. Aaron Wech has produced a bunch of tremor locations over the past week and has color coded them by date on the tremor localtion map. Tremor strength has decreased on the station HDW as the sources move north. They now seem to be north of the Olympic Peninsular. Garry Rogers reports that tremor in the southern Vancouver Island area continues, but at lower levels and less frequent intervals than before but that he can now see the tremor sources to the south of Vancouver Island. Herb Dragert of PGC reports that preliminary analysis of central Puget Sound GPS data reveal that southwest motion of 3-5 mm on selected stations (ETS like motion) can be detected over a region about 40 to 80 km stretching along the southeast flank of the Olympic Mountains. No GPS motion is seen on southern Vancouver Island stations (yet).
• Jan 24, 2007 - Tremor continues as before but fewer periods at very strong levels. It seems to be mostly concentrated under the western part of the Olympic Peninsula and moving slowly northward. Garry Rogers of the PGC reported today that moderate strength tremor was seen in southern Vancouver Island during at least 15 hours. This appears to be a startup of a tremor source totally separate from the Olympic Peninsula source that is still going on during the same time periods.
• Jan 22, 2007 - The central Sound tremor continues at strong to very strong levels. It also seems to be moving north-northwest from its original locations in the south-central Puget Sound. Some locations now are under the east Olympic Peninsula. There is evidence that sometimes more than one tremor source is active at the same time. Some tremor bursts are now being weakly detected on stations in the northern Puget Sound and southern Vancouver Island.
• Jan 20, 2007 - The strong tremor in the central sound has now continued for a week with the last several days showing continuous tremor with stonger and weaker periods. Some has been very strong. It almost saturates the record at HDW webicorder record today. The two week tremor envelope plot ending today shows the small amount of north Puget Sound tremor (green) and the build up and continuing activity, particularly on HDW and GNW of the south-central Puget Sound tremor (blue). We think that this is a real ETS event that will show on the GPS stations soon, but this is the central-south Puget Sound ETS, not the main north Puget Sound-south Vancouver Island one.
• Jan 16, 2007 - Strong tremor in the central zone continues today with a very strong tremor burst about hour 14:20 Z today. A sample of the three day RMS plot ending late today shows the increase over the last three days, particularly on HDW, GNW and some on JCW, but little seen on STW and MCW in the north. A Spectrogram of station HDW for the second half of today shows the extent and strength of the tremor. Ken Creager has produced a epicentral map of selected tremor bursts over the past week computed by cross-correlation timing of envelope functions.
• Jan 15, 2007 - Over the past day and a half most hours have had moderate to strong tremor in the central Sound zone. Since Jan 8 we have seen no tremor in the north zone, where the the main ETS usually starts.
• Jan 10, 2007 - This is frustrating. The northern Puget Sound tremor seems to have died down. During the past two days there are were first some periods of tremor in the northern Puget Sound area but they died out and for most of the last day only a few periods of low level tremor in the central sound but nothing much up north. Then to make matters worse another very strong wind storm has moved through and we lost our feed for all EarthScope stations for several hours, so who knows whats next.
• Jan 8, 2007 - Tremor has continued today with at least 7 hours having periods of weak tremor. Most is located in the north Sound area but a few weak bursts were seen in the central Sound section.
• Jan 7, 2007 - Maybe this is it. Last night had several hours with fairly strong tremor periods. It showed up on all stations in the north Sound area and thus is similar to the start of the main ETS tremor. Later in the day there were only a few and weaker tremor periods but were still identifiable even though there was a major wind storm going through at about the same time. A snapshot plot of the RMS graphs show te periods of strong tremor circled in green with a magenta line showing a filtered record section of many stations.
• Jan 3, 2007 - Stop the ETS! This is frustrating. Since early on Jan 1 there has been no apparent tremor activity anywhere. What the^%^$#?
• Jan 1, 2007 - It seems that the new year started with several hours early today with periods of localized (shallow?) tremor in the central sound. However later in the day the tremor seems to have stopped with nothing obvious later on.
• Dec 31, 2006 - Maybe just in time for the new year the ETS may be starting. Today there were several hours with short periods of weak but definite tremor in the central sound area.
• Dec 30, 2006 - There finally was possibly some very weak tremor this morning coming from the mid sound area. It was only a few small bursts of 60 seconds or so each. It would not be seen if there was much background noise and so may be nothing.
• Dec 18, 2006 - Well it seems that the wind storm of the century (evening of Dec 14 PST) did not shake loose the ETS. While many seismic stations were lost during this storm we still have key stations left to do the monitoring. Crews are again heading to the hills to try to fix those stations lost to the winds. What's next?
• Dec 9, 2006 - Still no tremor, but a break in the weather and huge efforts by PNSN and CAFE staff have almost all of the network going again. CAFE array telemetry has been turned off because of the extra battery drain but almost all stations have been serviced including those requiring clearing numerous fallen trees off roads and long snow shoe or ski hikes.
• Dec 7, 2006 - We are getting a bit nervous since there is still no tremor. But Herb Dragert, the epitime of calm gives the following based on his statistics. Nov 25 is the center of the expected window with plus or minus 35 days being the one sigma deviation so we still have some time to go before we may mention the dreaded word, "parkfield".
• Dec 1, 2006 - The recent bad weather in the PNW has taken a toll on both our network stations and the CAFE temporary stations. Repairs are underway in both cases and some sun will be a big help. In the mean time there still is no obvious beginning of the ETS. A few periods of very weak tremor may have occurred on Nov 29 but nothing obvious since then.
• Nov 22, 2006 - Still no tremor seen on Washington stations. Unfortunately the continuing series of storms make the records messy and we are having station outages now and then also. A key station, HDW failed last night. Two other stations in the CAFE arrays have also recently gone down.
• Nov 15, 2006 - The PNSN has a new tremor location algorithm up and running that is based on cross-correlations of envelope functions. So far 8 tremor events, occurring on November 10, 11, and 12, have been located. They all locate under Vancouver Island between Port Alberni and the Pacific Coast. As these locations are all outside our seismic network, location uncertainties are large, but the locations are consistent with what Gary Rogers is reporting. It appears that there is no tremor occurring under Washington State during this time. We have not seen any tremor on November 13 and 14. An example of a one hour envelope plot showing tremor coming from the north has one of the tremor periods circled in green.
• Nov 15, 2006 - Garry Rogers of PGC reports that the tremor in mid-Vancouver Island region stopped on Nov. 13. Still nothing obvious in southern Vancouver Island or Washington.
• Nov 13, 2006 - Kathleen Hodgkinson of UNAVCO provided a link for data from the PBO network (GPS, Borehole Strainmeters):
• Nov 12, 2006 - Garry Rogers of PGC reports that Nov 11 had 17 hours with some tremor and Nov 12 had 24 hours with some tremor, all in the region just north of Alberni (central Vancouver Island). The amount of tremor is consistent with an ETS event but most 14 month - south Vancouver Island ETS events start in the south and move north. Maybe this is the rare event that moves south, but no change in tremor locations are yet evident.
• Nov 10, 2006 - Garry Rogers of PGC reports there has been sporadic weak tremor coming from Mid Vancouver Island, just north of Alberni since November 5. At 23 hours UT on November 8 it started to become more serious. On November 9 UT there was 15 hours with some tremor and on November 10 UT there were 23 hours with some tremor. Hours 3,4,4,5, 10 and 14 on November 10 contained strong tremor. All is still coming from just north of Alberni.
  By way of background Garry reports that if we see 3 days of more or less continuous tremor it will continue much longer and is an ETS event and can be seen on GPS.
  Most of the "south island events", like the one we are expecting, have started in the south and migrated north. However we do have one that started to the north and migrated south. This might turn into another south migrating event it may be an independent mid island event. So far I can see no hint of a migration direction.
• Nov 10, 2006 - PNSN observed a brief episode of tremor November 9 at 1300 GMT and several more hours with tremor today. This is observed on several stations in northwest Washington, including the Big Skidder array and thus seems to be coming from the north.
• Nov 10, 2006 _ John Langbein of the USGS provides web pages summarizing the PBO borehole strain meters located around the Straits of Juan de Fucca. These may be found at: http://quake.wr.usgs.gov/research/deformation/twocolor/PBO_strain (Thanks to Herb Dragert for pointing this out.)
• Nov 10, 2006 - Herb Dragert of PGC reports that they have implemented a special ETS page to help track the upcoming ETS. This was be found at: http://tsea.pgc.nrcan.gc.ca:8080/wcda/etsmon_e.php (but has disapeared). He also reports that a few short periods of tremor have been observed in central Vancouver Island but not lasting long enough to qualify as the beginning of the ETS. ..... yet.
• Nov 9, 2006 - We have started the Experimental Spectrograms web pages again with selected stations that have shown tremor periods in the past. In particular station, HDW may show tremor as a bright band in the 2-6Hz range.
• Nov. 4, 2006 - Tim Melbourn reports that PANGA has a set of web pages specifically organized to help identify ETS transients. This can be found at: www.geodesy.org/pnwdaily (But has disapeared).
• Oct 27 - Creager and Love replaced a bad computer disk so telemetry from the Price Lake and Big Skidder arrays is running again.
• Oct 20 - Wech and Thelen deploy the last of the 62 seismometers at Penny Creek! They also replaced stolen batteries at one site of the Big Skidder Array and a noisy short-period sensor at the same array. The telemetry is temporarily down, but all 62 stations of the CAFE experiment are up and running.
• Oct 20 - Tim Melbourn of Central Washington Univ. (CWU) and the PANGA data processing center reports that his group is watching the geodetic and tilt data carefully for ETS detection and will have a summary web page up within a week.
• October 10, 2006 - Realtime monitoring via PNSN stations and CAFE started on a routine basis to detect the start of the next ETS. Web pages for envelope functions started. Special pages for ETS diagnostic Webicorders started.
• Oct 8 - Data looks as if one array station has been vandelized. Plans are made to take new equipment out and check it out.
• October 3-5, 2006 - Creager and Wech build the last vault and install six more seismometers. Only one to go!
• September 12 - After precautionary measures are taken, station PL04 survives 7000 cubic yards of rock being blasted out of rock quarry 150 feet away.
• September 4-7 and 20-24, 2006 - Wech, O'Donnell, Malone, Fattori Sparenza and Giannaccari complete the first full service run.
• August 21-30 - Offield, Alverez, Fort, Chavez and Carmichael install radio telemetry at Price Lake and Big Skidder Hill Arrays.
• July 27 - Field crews packed their bags and headed home after successfully deploying all 55 seismometers. The remaining seven seismometers were still being built and checked out. The equipment worked like a dream! The only equipment failures during the entire deployment phase were one DAS and one GPS clock, not to mention one broken pick handle and one bent breaker bar.
• July 9 - The first seismometer was deployed.
• July 8 - The ceremonial first hole was dug and first vault built.
• July 6-27 - Creager, Malone, Wech, Carmichael, and Kerr (from UW), Rondenay, Lev and Burdick (from MIT), Abers and Zhu (from BU), Azevedo and Miller (from Earthscope) and Frost (volunteer) all descend on the little town of Shelton, Washington to begin the vault building and sensor deployment stage. Field work was staged out of a warehouse run by the Port of Shelton.
• June 27-30 - Offield, Alverez, Chavez, Fort and Wech site telemetry for the Price Lake and Big Skidder Hill Arrays.
• June 12-July 1, 2006 - Wech, Carmichael, Ulberg, Malone and Kerr drive all over western Washington finding sites for most of the seismometers.
• April 24-25, 2006 - Rondenay, Abers and Creager go to Socorro, New Mexico for logistics training.
• Jan 1, 2006 - NSF three year grant for Cascadia Arrays For EarthScope (CAFE) starts

BACKGROUND INFORMATION

Previous Studies of ETS by UW scientists

• Summer of 2005 Deep Tremor Study

Other information about ETS

• Slow slip events and episodic tremor - from the Pacific Geoscience Centre of the Geological Survey of Canada.
• Geodesy and Slow Earthquakes from the Geodesy Labs of Central Washington University.

Acknowledgments

• Steve Malone of UW maintains this blog
• Tony Qamar of UW wrote the original tremor envelop plotting software
• Ken Creager and Aaron Wech of UW provide the cross-correlation location plots
• Bob Crosson of UW provide envelop functions from which cross-correlations are done.
• Garry Rogers of PGC provides routine update information on tremor observed in Canada
• Herb Dragert of PGC provides analysis plots of GPS data
• Tim Melbourne of CWU provides analysis and plots of GPS and long baseline tilt-meters data.
• Honn Kao of PGC provides routine tremor analysis for Canadian stations.
• Evelyn Roeloffs of USGS provides analsyis of borehole strain meter data
• USArray and Plate Boundary Observatory of EarthScope provide all sorts of data
• Pacific Northwest Seismic Network is supported by the USGS
• The CAFE experiment PIs are: Ken Creager, Geoff Abers, Steve Malone, Stephane Rondenay, Brad Hacker and Tim Melbourne and is supported by the National Science Foundation.