HR: 0800h
AN: G11A-1194    [Abstracts]
TI: Observations With High-Rate GPS and Accelerometers on the Verrazano-Narrows Bridge: Synergism in Geophysical Methods
AU: Smyth, A
EM: smyth@civil.columbia.edu
AF: Columbia University, 610 S.W. Mudd Building Mail Code 4709 500 W. 120th Street, New York, NY 10027 United States
AU: * Kogan, M G
EM: kogan@ldeo.columbia.edu
AF: Columbia University, LDEO 61 Route 9W, Palisades, NY 10964 United States
AU: Kim, W
EM: wykim@ldeo.columbia.edu
AF: Columbia University, LDEO 61 Route 9W, Palisades, NY 10964 United States
AU: Bock, Y
EM: ybock@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive IGPP 0225, La Jolla, CA 92093 United States
AB: Ground displacements caused by long period surface waves of the Sumatra 2004 earthquake exceeded 10 mm at teleseismic distances. They were clearly recorded by both seismometers and 1-Hz rate GPS at thousands of kilometers from Sumatra. We address the question of efficient combination of space geodesy and seismology by examining our observations with 5-Hz sampling rate GPS and strong motion accelerometers on the Verrazano-Narrows Bridge during the 2004 New York Marathon. The synergism of both methods allowed us to capture slow displacements and oscillations in a wide range of periods, inaccessible to either method alone. Such factors as the load of thousands of runners, the load of regular traffic, and the effect of thermal expansion of the bridge were investigated. In particular, we captured both by GPS and accelerometers the free oscillations at 7.8 s, most probably the first flexural mode. We used two very different methods of processing the high-rate GPS: the method of instantaneous positioning [Bock et al., 2000], especially designed for real-time applications, and the TRACK software [Herring, 2005], designed for postprocessing of batched observations; both yielded nearly identical results. With proper permanent deployment of GPS antennas and communication equipment, it is feasible to monitor bridge deformation in real time with sub-mm horizontal and vertical precision at a temporal resolution of 1-5 Hz.
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 1294 Instruments and techniques
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 9820 Techniques applicable in three or more fields
SC: Geodesy [G]
MN: Fall Meeting 2005