...... PNSN ETS HISTORICAL RECORD
Summer 2009 ETS
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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
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).
- 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
- Garry Rogers of PGC provides routine update information on tremor observed
- 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
- Routine operations of the Pacific Northwest Seismic Network is supported
by a cooperative agreement from the US Geological Survey, a contract from the
Battelle Pacific Northwest Laboratory, and funding from the State of Washington
and the School of Arts and Sciences of the University of Washington.
- Special funding for deep tremor studies has been made available from
EAR-Geophysics of the National Science Foundation and from EAR-EarthScope
Science of the National Science Foundation.
- The CAFE experiment PIs are: Ken Creager, Geoff Abers, Steve Malone,
Brad Hacker and Tim Melbourne and is supported by the National