Members Present: Steve Bartlett, Bob Carey, Marv Halling, Mark Mainridge, Chris Pantelides, Larry Reaveley, Barry Welliver, Les Youd

Members Excused: Rob Brantley, Gary Christenson, Peter McDonough, Boyd Wheeler

Members Present from UUSS/ANSS Working Group: Walter Arabasz, Sue Nava, Kristine Pankow, Jim Pechmann, and Natalie Arseneau (all from University of Utah Seismograph Stations, UUSS)

1. Background on ANSS, ANSS management structure, and objectives of meeting (Walter Arabasz)
2. Selection of chair and representative to Regional Advisory Committee for ANSS Intermountain West Region
3. Overview of new urban strong-motion network, siting choices, and status of information/data flow (Sue Nava)
4. Discussion among advisory committee regarding:

• conceptual plan for siting up to 20 new strong-motion instruments during FY2002
• considerations for instrumenting buildings and other structures
• other guidance
• future plan for committee

2. Selection of chair and representative to Regional Advisory Committee

Steve Bartlett was voted to be chair of the Utah Advisory Committee, and Marv Halling was selected to be the Committee's representative to the IMW Regional Advisory Committee. By agreement among participants in the IMW Region, one representative from each of the state-level ANSS advisory committees (for states which have such committees) is invited to serve on the Regional Advisory Committee.

3. Overview of new urban strong-motion network

Sue Nava gave a status report on 20 strong-motion stations installed during FY2000 and 20 more stations scheduled to be installed by September 30, 2001. Siting criteria were reviewed, and other information on the infrastructure of the new urban strong-motion network was described (see homepage for Utah's Strong Ground Motion Monitoring Network (http://www.seis.utah.edu/urban/).

4. Discussion among advisory committee and consensus guidance for FY2002

• Given uncertainty about the number of strong-motion instruments to be allocated to Utah, and USGS planning guidance that levels of effort in the six currently active urban areas may have to be reduced in FY2002, < 20 new strong-motion stations are envisioned for Utah in FY2002. Selection of specific sites for new strong-motion stations will be made by the committee at a future date when the number of stations is known. As part of the site-selection process, existing instrument sites will first be carefully reviewed.

• Important issues in Utah are free-field ground motions and soil-structure interaction; siting of instruments on thin stiff soils along the eastern margin of the Salt Lake Valley is important because new ground-motion maps prepared by Ivan Wong and others predict large amplification at short periods at such sites.

• The committee was informed about the workshop on Strong-Motion Instrumentation of Buildings, planned for November 2001. Their preliminary consensus about instrumenting buildings in Utah is as follows: (1) the strategy of instrumenting buildings in areas such as California, where strong earthquakes are more frequent, is a good one (because information on building response is more transportable than ground-motion information); (2) notwithstanding item (1), the committee favors instrumenting some buildings in Utah—suggesting that roughly 20 to 25 percent of the FY2002 allocation of instruments be placed in buildings.

• Some members of the committee urge the siting of free-field instruments adjacent to two highway bridges in the Salt Lake Valley which will be permanently instrumented with deformation-measuring devices for structural analysis. A new highway bridge along the I-15 corridor in Salt Lake City was recently instrumented with 18 accelerometer channels and an adjacent free-field instrument (the latter, as part of the University of Utah's real-time network). A proposal has been submitted by Les Youd and others to the Utah Dept. of Transportation (UDOT) to install a down-hole strong-motion array close to this same highway bridge.

• Most members of the committee were optimistic that building and facility owners in the private sector could be persuaded to pay for strong-motion instruments as part of ANSS growth in Utah. Some members routinely advise and influence major utilities, hospital networks, and other building/facility owners, and they based their judgement on their working experience with such contacts.

• There was unanimous concern about acquiring quick ground-motion information when moderate-sized earthquakes occur near growing population centers in Utah outside the Wasatch Front area, such as Richfield (central Utah), St. George and Cedar City (SW Utah), or along the Utah-Idaho border—all seismically active areas. The strategy of either seeking state funding or using ANSS funding to instrument these areas was left for future consideration, depending on ANSS growth.

     Minutes reported by Walter Arabasz

 

 

 

 

 

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