HR: 0800h
AN: G11A-1197    [Abstracts]
TI: Ground Truth Accuracy Tests of GPS Seismology
AU: * Elosegui, P
EM: pelosegui@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138 United States
AU: * Elosegui, P
EM: pelosegui@cfa.harvard.edu
AF: Consejo Superior de Investigaciones Cientˇficas, IEEC/CSIC, E-Nexus 201, Gran Capita 2, Barcelona, 08034 Spain
AU: Oberlander, D J
EM: doberlander@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138 United States
AU: Davis, J L
EM: jdavis@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138 United States
AU: Baena, R
EM: rbaena@ieec.fcr.es
AF: Consejo Superior de Investigaciones Cientˇficas, IEEC/CSIC, E-Nexus 201, Gran Capita 2, Barcelona, 08034 Spain
AU: Ekstrom, G
EM: ekstrom@eps.harvard.edu
AF: Harvard University, 20 Oxford Street, Cambridge, MA 02138 United States
AB: As the precision of GPS determinations of site position continues to improve the detection of smaller and faster geophysical signals becomes possible. However, lack of independent measurements of these signals often precludes an assessment of the accuracy of such GPS position determinations. This may be particularly true for high-rate GPS applications. We have built an apparatus to assess the accuracy of GPS position determinations for high-rate applications, in particular the application known as "GPS seismology." The apparatus consists of a bidirectional, single-axis positioning table coupled to a digitally controlled stepping motor. The motor, in turn, is connected to a Field Programmable Gate Array (FPGA) chip that synchronously sequences through real historical earthquake profiles stored in Erasable Programmable Read Only Memory's (EPROM). A GPS antenna attached to this positioning table undergoes the simulated seismic motions of the Earth's surface while collecting high-rate GPS data. Analysis of the time-dependent position estimates can then be compared to the "ground truth," and the resultant GPS error spectrum can be measured. We have made extensive measurements with this system while inducing simulated seismic motions either in the horizontal plane or the vertical axis. A second stationary GPS antenna at a distance of several meters was simultaneously collecting high-rate (5 Hz) GPS data. We will present the calibration of this system, describe the GPS observations and data analysis, and assess the accuracy of GPS for high-rate geophysical applications and natural hazards mitigation.
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