...... PNSN ETS HISTORICAL RECORD

Summer 2009 ETS

Deep Tremor in Cascadia - The Array of Array experiment
March, 2009-.... (Summer 2009)
A continuation of, Cascadia Arrays For EarthScope (CAFE) -

Shortcuts:
Main Tremor Index | Interactive Tremor Map | Compare Maps | PGC TAMS/SSA |

This page will have frequent updates from observations and studies of Cascadia deep tremor during the Spring and Summer of 2009 associated with the Array of Array experiment for 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.

There is a map of AofA planned locations for operation during short periods during the summer of 2009 through fall of 2010.

NEWS (latest at the top)

June 4, 2009 - YEP. The AofA has missed this early ETS totally. It is now over and we had no new instruments installed. Fickle tremor! Garry Rogers of PGC (besides laughing at us) reports that there were two other back-to-back ETS-events determined by old seismic records only for which the inter-ETS times were less than a year. So when will the next one be? We should be ready for anything between early next spring and late next summer. Uhmmmm. In the mean time we will play at learning how to install, operate and interpret the data from 7-8 20-station arrays.
May 23, 2009 - OH DEAR! This ETS came almost three months early and is now mostly over. Starting about April 27 in the southern Puget Sound and gaining hours and strength over the next week it seemes to have peaked, passing under the northern Olympic Pinensula coast on or about May 10 and then moving into southern Vancouver Island shortly there after. It now seems mostly over from our perspective with the PGC still reporting some tremor in south central Vancouver Island.
This is playing havoc with the planned AofA experiment. We had counted on the ETS going off in July or August. The planned install time was early to mid June. Some of the equipment is still arriving. Currently our plans are to go ahead and install the arrays, run the full complement for a couple of weeks to get some background data (maybe some minor tremor if we are lucky) and then remove the Texans and turn off some of the RT-130s to conserve batteries. Later in the fall (or if tremor seems to pick up again) we will power back up some/most of the arrays to run through the spring and for the next ETS. It will arrive either early or late or on time, we are sure.
May 10, 2009 - Tremor seems to be continuing and maybe increasing in the south Puget Sound area with some also to the north along Hood Canal.
May 4, 2009 - Based on Aaron's automatic tremor location he reports ~60 hours of tremor during the last week and placed a request to Tim Melbourne to check on possible GPS signals from the nouthern Puget Sound. Aaron also reports the following "interesting observations":
1. Using the same methodology and stations, I have now detected more inter-ETS tremor since the May 2008 event than I did between the '07 and '08 events. 206 hours now vs. 181 between '07 and '08 ETS.
2. This tremor seems to be migrating north toward a region that just had 68 hours of localized tremor activity in March. With the hypothesis that the March "episode" bled off moment, I'm curious to see if the current tremor area migrates through this region or stops short of it.
April, 2009 - Orders for equipment and batteries for this summer's experiment were finalized and a deployment schedule starting June 15 was set (day after the Hood Canal bridge re-opens). Aaron Wech completed automating his tremor location routine and set up an Interactive Auto-Tremor Map.
March, 2009 - Planning for array locations has been underway since last fall. Several siting trips have been taken and preliminary sites have been chosen for seven possible sites. Permitting is under way for the use of these sites.
March 4, 2009 - A new special tremor page is started for the expected ETS of summer 2009 and for the AofA experiment. (Some linked web pages are not yet functional for the coming ETS but will be by this summer).

Acknowledgments

Steve Malone of UW maintains this blog
Tony Qamar of UW wrote the original tremor envelope plotting software
Ken Creager and Aaron Wech of UW provide the cross-correlation location plots
Bob Crosson of UW provide envelope functions from which cross-correlations are done.
Aaron Wech has developed the automatic cross-correlation, tremor location processing routines.
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 and Wendy McCausland of USGS provides analsyis of borehole strain meter data
John Langbein of USGS provides strain meter analysis plots.
USArray and Plate Boundary Observatory of EarthScope provide all sorts of data

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