April 2, 2004
HPWREN and SCIGN - Streaming high-frequency, real-time GPS data
The Southern California Integrated GPS Network (SCIGN) consists of 250+ continuous GPS stations established over the last decade to monitor crustal deformation, and associated seismic hazards, across the diffuse Pacific - North America plate boundary in southern California. Positional accuracy is about 1 mm horizontally and 3-4 mm vertically using 24-hours of GPS carrier phase and pseudorange measurements sampled at a 30-second rate, which is sufficient to compute site velocities with a precision of less than 1 mm/yr, as well as coseismic and postseismic deformation. In 1999, the SCIGN network captured motions from the Hector Mine earthquake in the Mojave desert. Researchers at SIO discovered that the GPS data could also detect the seismic waves emanating from this earthquake, including dynamic motions in the Los Angeles basin lasting several minutes due to basin resonance effects. An effort was initiated to increase the sampling rate of select SCIGN sites to 1 Hz and stream the data back to SIO in real-time. First efforts were in Orange County and the Parkfield region in central California. The Orange County Real Time Network (OCRTN) was performed in collaboration with OC's Public Resources and Facilities Division, since the same data that were useful for "GPS Seismology" could also be streamed in real-time to surveyors who could then position their GPS equipment with respect to the geodetic backbone provided by the upgraded SCIGN sites with centimeter-precision in real-time.
SCIGN high-frequency, real-time upgrades are now occurring in San
Diego and Riverside Counties in collaboration with the HPWREN and
ROADNet projects. HPWREN's Toro Peak facility is being used to
transmit 1 Hz data from 6 sites near Palm Springs that span the San
Andreas fault back to UCSD, and plans are underway to upgrade
additional sites in these two counties by leveraging this and other
HPWREN infrastructure (see figure below).
In the future, we expect that HPWREN communications infrastructure
will be used to support high-rate data flow from Plate Boundary
Observatory (PBO) sites in southern California, part of NSF's
-- by Yehuda Bock, Director, Scripps Orbit and Permanent Array Center (SOPAC) and California Spatial Reference Center (CSRC). For additional information, please check http://sopac.ucsd.edu.
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