HR: 0800h
AN: G21A-0129    [Abstracts]
TI: Progress towards a multiple-use GPS array in the Puget Sound region
AU: * Miner, A M
EM: minera@geology.cwu.edu
AF: Geodesy Laboratory & PANGA Data Analysis Facility, Department of Geological Sciences Central Washington University, Ellensburg, WA 98926 United States
AU: Miller, M M
EM: meghan@cwu.edu
AF: Geodesy Laboratory & PANGA Data Analysis Facility, Department of Geological Sciences Central Washington University, Ellensburg, WA 98926 United States
AU: Santillan, V M
EM: marcelo@geology.cwu.edu
AF: Geodesy Laboratory & PANGA Data Analysis Facility, Department of Geological Sciences Central Washington University, Ellensburg, WA 98926 United States
AB: The cooperative Puget Reference Station Network (PRSN) array of continuous GPS stations (CORS or CGPS) in western Washington provides targeted densification of the Pacific Northwest Geodetic Array (PANGA) around the Seattle fault and above an areas of the Cascadia subduction zone known to experience recurring silent earthquakes. Public agencies equip and operate PRSN stations, while the university coordinates siting and provides stable monuments. To date, 8 deep drill-braced, 1 shallow drill-braced, and 3 H-pile monuments enhance this network to geodetic standards for studies of solid earth deformation. Full operation of the network is anticipated for summer 2005, with approximately 18 stations. The network provides both real-time corrections for surveying applications and files for post processing at a nominal 1-second sampling interval. The main scientific goal of the project is to increase the density and quality of CORS in the Puget Sound region, in order to measure strain accumulation across the major structures (e.g., the Seattle fault, regional creep events). This will require monitoring over at least the next few years, yet new stations have already contributed to better understanding subduction-related slow earthquakes. Combined with close seismic monitoring, the new GPS stations indicate that the most recent episode of tremor and slip (ETS) occurred in at least two phases. The first occurred in late March-early April of 2004 and affected southern Puget Sound. This was followed somewhat tardily by a larger, predicted event in northern Puget Sound in July. The two areas appear to correspond to the two limbs of the arch in the subducting Juan de Fuca plate; some past events have shown similar progression but were not as well documented. Advances in real-time horizontal positioning no longer require particularly dense networks, but the PRSN provides denser (~30 km) spacing that resolves subtler deformation. In addition to bracketing structures with better density than the Plate Boundary Observatory (PBO), the network provides redundancy and autonomy for individual agencies, and should facilitate increasing use of GPS for leveling. Some strengths of the cooperative approach have been efficient use of limited resources by surveyors and scientists, as well as fostering communication between public, private and academic GPS users. The main drawback is that the time required to establish a station is approximately proportional to the fourth power of the number of agencies involved. However the end result should be an unusually stable, robust, and flexible network that is not strongly dependent on any one source of funding.
UR: http://www.geodesy.cwu.edu
DE: 1208 Crustal movements--intraplate (8110)
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 1247 Terrestrial reference systems
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting