Status report to CoCom and Board of Directors EarthScope Transportable Array RW Busby, 15 April 2013, revised 26 April 2013 Executive Summary Transportable Array is operating well within budget and schedule targets. Transportable Array ended Y5 month 5 (February 2013 close) of five year Cooperative Agreement with a positive cost variance (underspent) of 5% of annual budget, a variance of $548k. The project did not rebaseline in Year 3 or Year 4 but had informally agreed with NSF in Y3 to carry forward $1.1M into Y5 for contingent activities. In terms of schedule, operations are on plan: installation and construction are 7 stations behind (9 days) the plan due to wet ground, permitting is 12 stations from completion, removal is on plan (including removing some straggler vaults). TA has pursued contingent activities related to deployment in Alaska that includes installation of five test stations, permitting activity on four additional stations this summer. TA has established a warehouse/office facility in Anchorage staffed by a new HTSI position, Alaska Deployment Coordinator Brian Coyle. The TACO Station Coordinator, Steve Welch, retired in Dec 2012 and the position will not be filled. A new subaward is nearly in place with University of Alaska Fairbanks which would support three full-time positions. Cascadia and Reference Array station operation has been nominal. Report Budget Status Transportable Array ended Y5 month 5 (February 2013 close) of the five year Cooperative Agreement with a positive cost variance (underspent) of 5% of annual budget, a variance of $548k. The Current Year Spend Plan (CYSP) for year 5 of the Cooperative Agreement is shown below. A number of projected Alaska Operations tasks have yet to be reclassified from construction and permitting TA Status report 4/26/2013 Page 1 Y5 Projections as of Feb 2013 Close 3.4.2 Transportable Array 3.4.2.1 TA Management Y5 Funding 584,111 3.4.2.2.1 TA Maintenance/Repair/Replacement 1,900,480 REVENUE FROM ADOPTED STATIONS (152,680) Sep-12 adjustments Carryover between tasks (6,542) 247,417 (935,648) 112,159 1,381,469 (112,159) 42% of period CFY actuals / Projected total Total Available 824,986 Total Projected 590,392 2,346,301 2,431,919 (152,680) (222,845) estimated variance 234,594 (85,618) CFY Actuals 229,735 39% Y4 Actuals 861,269 837,687 34% 2,015,838 70,165 (32,225) (178,459) 3.4.2.2.2 TA Alaska Facilities - - - - 46,838 (46,838) 62,595 134% 3.4.2.2.3 TA Alaska Operations - - - - 343,763 (343,763) 152,640 44% 3,887,262 (172,797) 1,392,368 36% 3,135,562 607,659 3.4.2.3 Array Operations - 3,472,106 1,265,019 (1,022,659) 3.4.2.4 Station Deployment 3.4.2.4.1 Removals 515,188 672,692 (612,342) 575,538 656,688 (81,149) 326,766 50% 3.4.2.4.2 Permitting 857,046 880,599 (234,934) 1,502,711 1,218,351 284,360 281,962 23% 912,552 (187,275) 522,011 1,899,821 1,829,096 70,724 584,386 32% 1,879,067 1,107,304 486,971 (280,961) 10,001,320 2,175,816 3.4.2.4.3 Construction 3.4.2.4.4 Installation 3.4.2 Transportable Array 1,565,085 0 3,714,465 - 1,313,315 1,323,225 (9,911) 719,959 54% 950,275 12,177,137 12,327,534 (150,397) 4,588,098 37% 10,362,222 The project did not re-baseline in Year 3 or Year 4 but had informally agreed with NSF in Y3 to carry forward $1.1M into Y5 for contingent activities. Projections to year-end forecast a $150,00 overspend on TA and $50,000 on Cascadia. A key to accurate projections for year end spending and the overall cost management of the project is tracking unit costs against plan. The table below shows the planned unit costs and the chart gives an estimate of actuals for the last two years. The budget versus actuals for construction suffers from an accounting issue where the stated budget does not include IRIS costs, only subaward budgets. The budget is closer to $11,000. per/ station $ Removals Construction Installation TA Status report 4/26/2013 Trend, 2 years budget Actuals $3,000 $3,600 $7,000 $9,200 $4,250 $4,250 Page 2 $20,000 $18,000 $16,000 Construction unit cost $14,000 $12,000 $10,000 Install Unit cost Removal Unit cost $8,000 $6,000 $4,000 Linear (Construction unit cost) Linear (Install Unit cost) $2,000 $- Linear (Removal Unit cost) Schedule Status As of April 14, operations are on plan: installation and construction are 7 stations behind (9 days) the plan due to wet ground, permitting is 12 stations from completion, removal is on plan (including removing some straggler vaults). The planned installation schedule is overlain on a current TA status map as of 4/9/2013 TA Status report 4/26/2013 Page 3 TA Status report 4/26/2013 Page 4 Cascadia and Reference Array station operation has been nominal. In Cascadia, a maintenance episode is planned for the summer to refresh batteries and, where necessary, replace media sticks at all stations. A new battery design will be implemented that changes the large reserve batteries from single use alkaline to rechargeable AGM lead acid. This has a higher initial cost but reduces annual service visits in the SAGE budget. That expense will likely exhaust ARRA funds for this project. Y5 Projections as of feb 2013 close Transportable Array -Cascadia Y5 Funding 7,101 Total Available 64,460 Total Projected 1,387 DMC 24,997 27,110 32,493 (5,384) TA Maintenance/Repair/Replacement 41,959 97,410 59,354 38,055 138,881 77,010 183,961 (106,951) 76,031 35,907 (57,494) 35,907 TA Management Array Operations estimated variance 63,072 CFY Actuals 1,387 12,999 (132,271) 3.4.2.4 Station Deployment Construction - (21,587) Installation - (15,164) Transportable Array -Cascadia 212,938 261,035 (5) 313,098 (15,159) (5) (52,062) (5,952) Contingent Activities Canada deployment will continue this summer, subject to approval by NSF, deploying 28 additional stations. The geographic area is smaller this year and the stations not quite as remote as some last year. Procedures for transiting the border for crew and equipment are expected to be simpler due to existing work permits and custom broker arrangements. TA has pursued contingent activities related to deployment in Alaska that includes installation of five test stations (see report Appendix A) and additional dialogs with stakeholders including BLM, NOAA and ATWC, and the AEIC at University of Alaska Fairbanks. An additional contingent activity was the purchase of a helicopter portable drill capable of auguring or coring holes to 8” diameter, but this has not been delivered. Meetings and Presentations AGU Fall Meeting 2012 American Meteorological Society, Jan 2013 PGC Victoria, GEM workshop Vancouver, Feb 2013 Polar Technology Workshop, April 2013 European Geophysical Union, April 2013 TA Status report 4/26/2013 Page 5 Seismological Society of America April 2013 Activities of Governance Committee (3) TAWG webinar presented (1) TAWG status briefing USAAC last met Dec 1-2 2012. Reports from that meeting are presented separately by USArray Director. A conference call was held April 15 to review status, spend down plans and provide input on governance recommendations. Considerable discussion focused on input to the TA Scope Management Plan that identifies community priorities in the operational choices available to USArray management to address cost and/or budget pressure. Activities related to NSF Property transfers have been completed related to station adoptions in Arkansas, Ohio, Purdue and Yukon. A meeting at EAR Division Director Wendy Harrison’s office on Feb 15 to discuss integration with Polar Programs and a follow-on meeting with the Division director of Atmospheric and Geospace Sciences Michael Morgan. 6 hours later the Chelyabinsk Meteor exploded to produce the largest infrasound source in recent history, fittingly an atmospheric event by a geospace object. In the subsequent days a special event page was produced by IRIS DMC http://www.iris.edu/dms/nodes/dmc/specialevents/2013/02/19/chelyabinsk-russia-bolide-meteor/ and this was followed by an NSF press release http://www.nsf.gov/news/news_summ.jsp?cntn_id=127114&WT.mc_id=USNSF_51&WT.mc_ev =click Several discussions related to CEUSN; USGS in January, NSF in Feb and several phone/emails Media and others The TA hosted a delegation from ChinArray December 14 at IRIS HQ and a visit to station O55A in PA Dec 15. The Weather Channel filmed installation of S59A Friday April 12. This aired April 26, on “Good Morning with Al”. A congressional and NSF site visit is planned to Q59A near Annapolis MD on May 2. TA Status report 4/26/2013 Page 6 Appendix A: Sensor Burial Tests Report – Second edition Updates from POKR POKR.01, HDA, TCOL, EPYK, TASN, TASO DRAFT: Sensor Emplacement Tests for TA Seismic Stations in Alaska By: The IRIS Instrumentation Services Team In preparation for redeploying EarthScope’s USArray Transportable Array (TA) to Alaska beginning in 2014, IRIS has been exploring new strategies for sensor emplacement. These efforts are necessitated by the conditions unique to operating in Alaska, where sparse road access limits available equipment and hardware at sites, and permafrost may prevent the widespread use of the standardized TA vaults that have been used successfully across the lower-48. This work is also motivated by the recent availability of several models of broadband seismometers designed for shallow boreholes. Replacing the TA vault sensors used in the lower-48 with these instruments will be a major cost driver for the seismic component of EarthScope in Alaska which is accounted for in the replacement equipment from the CEUSN project. To this end, we have undertaken several tests to evaluate the placement and performance of these types of sensors in various emplacement scenarios. The primary goals of this work are to; 1) develop a procedure for reliably and economically deploying these seismometers; 2) understand the limitations and advantages of shallow boreholes; and 3) maintain or improve the high standard of both quantity and quality of data produced by TA stations in the lower-48. In this report we describe the current performance of TA stations, discuss several borehole sensor emplacements, and present the initial results of these studies. Evaluating a TA station’s performance uses a probability density function (PDF) created by combining the power spectral density (PSD) values calculated from one hour segments of continuous seismic records (McNamara and Buland, 2004). This shows the characteristic spectra recorded by each channel of a seismometer, ideally for a station deployment encompassing multiple seasons. The result for a single channel maps the probable occurrence of power as a function of period for the signal, emphasizing the sensitivity of the station to background noise spectra as energy from earthquakes and short-term instrument signal recede into the background probability. In North America quiet stations show spectra that reside close to the global low noise model (Peterson, 1993) but conform to a somewhat higher minimum low noise model (McNamara and Buland, 2004) and have probabilities that concentrate along a narrow range of signal power (Figure 1). The character is significantly different between vertical and horizontal components. Signal power exhibits a strong frequency dependence coinciding with the oceanic microseism that is prevalent at periods between approximately 5 and 15 seconds and forms a broad peak 20-40 dB higher than the adjacent spectrum. Stations with relatively quiet spectra outside the microseism will effectively record local and regional seismicity and research-grade teleseismic arrivals, respectively, producing data ideal for the community to fulfill the primary scientific objectives of the USArray. TA Status report 4/26/2013 Page 7 Figure 1: From McNamara and Buland, 2004. A characteristic PDF plot of summed PSD estimates for a broadband seismometer (left) and minimum noise levels measured from PDFs for stations in the USNSN and ANSS (right). Lower-48 Station Performance The mean behavior of the lower-48 TA shows expected seasonal (Figure 2) and geographic (Figures 3 and 4) variations in its signal. Microseismic noise coincident with oceanic storms in the northern hemisphere is 20-30 dB stronger during the winter (Figures 2 and 3). Short period noise is slightly stronger in the summer, probably due to wind, thawed ground, and increased human activities, particularly in rural fields where the stations are predominantly located. Long period signal appears to correlate seasonally as well, mirroring the microseismic behavior. While the spectral characteristics of the horizontal and vertical channels are generally similar, signal is ~20 dB stronger on horizontal channels and thought to be related to the admittance of atmospheric pressure variations which produce a tilt on the sensor. This suggests that conditions of the sensor emplacement and potential insulation from pressure variations should have a strong affect on horizontal noise levels. TA Status report 4/26/2013 Page 8 Figure 2: Power measurements for five representative periods averaged for all TA stations and plotted as a function of time (left) and as a histogram (right). Sensitivity to long period noise (green) distinguishes the behavior of signal power on horizontal channels when compared to the vertical channel. Signal power at TA sites shows regional trends. Relative to the lifetime mean TA performance, stations in the intermountain west were the quietest, residing about 5-10 dB below average in January and 15-20 dB below average in August for long period signal. Stations in the Ohio and Tennessee Valleys also perform near this level. Coastal stations are quieter at long periods during the summer but appear less sensitive to this seasonal variation. In contrast, stations across the Great Plains, Mississippi Valley, and Gulf Coast exhibit noise at least 5-15 dB higher than average throughout the year. Across the array, short period noise is seasonally consistent at 20-25 dB above average along the coasts and the northern Great Plains but 15-20 dB below average within the intermountain west. Improved noise performance along the easternmost TA stations may result from switching to a watertight, rotomolded tank design to prevent occasional instances of flooding. The TA station quality in much of western North America demonstrates the advantage of operating in a sparsely populated and utilized region, while proximity to natural (ocean) or anthropogenic (agriculture) noise results in a lower station performance. Figure 3: Residual power measurements for January (left) and August (right) at 6.4 seconds period following removal of the mean power measurement for the lifetime of the TA. These performance trends can be further explored here: http://crunch.iris.washington.edu/stationinfo/historic_station_ranking_Jan/ http://crunch.iris.washington.edu/stationinfo/historic_station_ranking_Aug/ TA Status report 4/26/2013 Page 9 Figure 4: Residual power measurements for January (left) and August (right) at 102.4 seconds period following removal of the mean power measurement for the lifetime of the TA. Test Stations Since August 2011 six stations, operating eight seismometers, have been deployed in Alaska/Yukon to evaluate installation procedures and noise performance of shallow borehole sensors. In addition, a set of 5 boreholes and two cored holes have been created at ASL in which we have tested 14 separate installations of sensors-typically with four operating simultaneously. One additional test station was established (TA.TFRD) within the Anza array in southern California that compared a surface outcrop STS-2 versus a 1.5m cored hole into the outcrop. The station operated for six months and removed. TOLK The site at Toolik Lake Field Station on the North Slope of Alaska functions as a prototype for Alaskan TA stations. The surface geology consists of alluvium and permafrost overlain by an artificial 1 m thick gravel pad. Three 12” holes were augered and cased with PVC pipe. The pipe is divided into two segments, decoupling the lower segment containing the sensor from any movement imparted on the upper segment by the freeze-thaw cycle of permafrost. A CMG3T sensor was lowered into two of the holes and oriented. The station experienced two months of downtime due to power issues in its first and second winter but otherwise the seismometer has operated continuously since being installed. PDF-PSD estimates show that especially for long period horizontal noise, TOLK is the quietest overall stations in the entire TA (perhaps yielding to POKR, also in Alaska). Although emplaced at different depths, both sensors produce essentially the same response. The station performs very well during the winter at over 25 dB below the TA average. This may be due to the frozen overburden isolating the influence of pressure changes on sensor tilt. This effect moderates in the summer, shown by an increase in long period noise, but is still ~10 DB below the average. The station is noticeably quieter at short periods than the Alaskan GSN borehole seismometer COLA (Figure 5) emplaced at 120 m depth. In the summer, both the long period and short period noise increases, whereas the microseism noise is stronger in the winter (see figureThere is more variability due to the aforementioned seasonal response at TOLK, but both the long period and short period responses are ~10 dB lower on average. TA Status report 4/26/2013 Page 10 Figure 5: Comparison of PDF-PSD estimates for 2012 from all three channels at TOLK and COLA. Figure 6. An 18 month timeseries of discrete spectral bands for the side by side borehole sensors at TOLK. TA Status report 4/26/2013 Page 11 Table 1: TA Stations operating or planned in Alaska and Yukon. Station Location Hole Type Sensor TA.TOLK.-- Toolik Lake, AK TA.TOLK.01 Toolik Lake, AK TA.TCOL.-- CIGO, Fairbanks, AK (adjacent to COLA) CIGO, Fairbanks, AK (adjacent to COLA) Harding Lake AK (replaced AK.HDA) Poker Flat Research Range, AK Poker Flat Research Range, AK Poker Flat, AK Eagle Plains, YT Sachs Harbor NWT Paulatuk, NWT Barrow AK Middleton Is. AK Augered 12” PVC casing Augered 12” PVC casing Augered 8” PVC casing TA.TCOL.01 TA.HDA.-TA.POKR.-- TA.POKR.01 YE.PIC3.01 TA.EPYK.-TA.A36M TA.C36M TA.A21K TA.Q23K Started CMG3T Depth (m) 5 CMG3T 4 8/13/2011 STS-4B 10 10/9/2011 Augered 8” PVC casing STS-4B 5 10/9/2011 Augered 8” PVC casing T120PH 5 10/4/2012 TA Tank into rock T240 2 10/12/2012 Augered 8” PVC casing T120PH 5 10/12/2012 Hand dug, 1M Cored in rock 6” PVC 6” PVC 6” PVC 6” PVC T120PH T120PH T120PHQ T120PHQ T120PHQ T120PHQ 1M 1.4 5M 5M 3M 5M 10/15/2012 5/2013 5/2013 6/2013 8/2013 8/13/2011 Figure 7 Location of Test stations in Alaska and Yukon TA Status report 4/26/2013 Page 12 Figure 8 Two month PDF comparison of TA Tank and a 5M posthole located at Poker Flat Research Range, near Fairbanks. Below shows performance of an additional 1M direct buried posthole sensor. As temperatures have warmed, the performance of the 1M hole has degraded considerably due to pressure induced tilts. TA Status report 4/26/2013 Page 13 Figure 9 Performance of a 1.5m cored hole just off the Dempster "Highway" near Eagle Plains Yukon. TA Status report 4/26/2013 Page 14 Testing of posthole and borehole sensors at ASL A suite of five postholes and two cored holes were created at and in cooperation with Albuquerque Seismological Laboratory, New Mexico. These stations are adjacent to GSN station ANMO that contains KS54000 primary and CMG3T secondary sensors buried at 145 m and 57 m depths, respectively. TA Status report 4/26/2013 Page 15 New US Array/ASL Boreholes Existing ANMO Pad N 10.0' E W S 3m 6" ID PVC Casing 180" 5m 6" ID PVC Casing 5m 6" ID PVC Casing 10m 6" ID PVC Casing 5m 8" ID PVC Casing 36" 108" 108" 3" Steel Conduit Existing 5' X 5' ID Pit, 5' Deep (6' X 6' Outside dimension) 36" 30" New Solar Panels 30m 7" OD Steel Casing 36" 60m 7" OD Steel Casing 132" Station TASM uses augered holes in diameters of 8” and 6” diameters but is otherwise similar to TOLK with seismometers at 5 and 10 meters depth in alluvium. Station TASL utilizes holes TA Status report 4/26/2013 Page 16 cored 6” or 8” inches diameter and ~48” deep into fractured Precambrian Granite. These holes were drilled with a portable coring machine, which is small enough in size and weight to be transported in a pickup truck or via fixed-wing aircraft and/or helicopter to sites throughout Alaska. The coring procedure requires a relatively stable surface, about 10 gallons of recyclable water, and three hours of work depending on site conditions. The direct emplacement of the seismometer in hard rock may avoid upheaval of the instrument due to changes in permafrost, complications with PVC casing, and should provide good coupling with the surrounding environment. Preliminary results show that although TASL and TASM do not perform to the level of ANMO’s deep borehole sensors, at long and short periods they equal or slightly exceed the performance of TA station W23A, installed nearby in a traditional vault from 2008-2010 (Figure 6). Figure 6: Comparison of PDF-PSD estimates for 2012 from the BHN/BH2 channels at TASL, TASM, ANMO (00-KS54000), and TA station W23A. Plots from TASL/TASM reflect an artifact from temporary application of digitizer preamps which were not included in the metadata. TFRD TFRD is cored similarly to TASM and installed adjacent to AZ network station FRD, which resides in a surface vault that is subject to large temperature variations. The cored hole exceeds the long period performance of the AZ station by 30 dB (Figure 7), showing a dramatic improvement in the overall response obtained at this location. TA Status report 4/26/2013 Page 17 Figure 7: Comparison of PDF-PSD estimates for 2012 from the BHN channels at FRD and TFRD. Future Work The TA plans to install additional test stations in the Alaska / Yukon work area to further investigate sensor emplacement, especially concerning effects of freezing and thawing. These stations are listed in Table 2 above, all data is available from the IRIS DMC. Metadata in some instances may temporarily not reflect actual operation and fine details of sensor swaps and details of the emplacement are available upon request. References McNamara, D.E., and R.P. Buland (2004), Ambient Noise Levels in the Continental United States, Bull. Seismol. Soc. Amer., 94, 1517–1527. Peterson, J. (1993), Observation and Modeling of Seismic Background Noise, U.S. Geol. Surv. Tech. Rept., 93-322, 1–9 TA Status report 4/26/2013 Page 18