Data and data processing

The BARD network is a permanent GPS network comprising 40 GPS sites, installed since 1994 in Northern California (Romanowicz et al., 1994). Some of these sites have been transferred to the Plate Boundary Observatory (PBO), but not all. The receivers operating are mainly Ashtech (Z-12 and $\mu Z$) and Trimble receivers (TR4000) with Choke Ring antennas. During the last two years, the network was upgraded, replacing the old receivers (mostly Ashtech Z-12) by Trimble NETRS with high-rate capabilities. The BARD network is streaming data to the Berkeley Seismological Laboratory in real-time (from 1s to 15s) (Romanowicz et al., 1994). All the data are archived at the Northern California Earthquake Data Center (NCEDC, http://www.ncedc.org) (Neuhauser et al., 2001). Today, the BARD network has operated long enough to provide high accuracy velocities in the San Francisco Bay Area (Blewitt and Lavallée, 2002).

Figure 2.40: Map of the permanent GPS benchmarks of the BARD (black triangles) and PBO (white squares) networks. The sites HCRO (Hat Creek Radio Observatory), PKDB (Parkfield, CA), SAOB (San Andreas Geophysical Observatory) and YBHB (Yreka Blue Horn Mine, CA) are located outside the map.
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All the data have been processed by using the GAMIT/GLOBK tool suite (King and Bock, 2006, Herring, 2005). We have adjusted all the 4018 daily solutions using five reference sites (BAY1, GOLD, JPLM, PPT1, VNDP) that are present in our dataset and included in the ITRF2000 release (Altamimi et al., 2002). The adjustment of the whole dataset of daily solutions was succesfully completed by minimizing the shifts between the ITRF velocities and our solutions.

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