Data archival

The Northern California Earthquake Data Center (NCEDC), operated jointly by the BSL and USGS, archives all permanent-site GPS data currently being collected in northern California. In the past months, and due to the transition to PBO, some sites are not present in the NCEDC archive (PPT1 for instance). All the sites available will be archived as in the past. We archive the Federal Aviation Administration (FAA) sites all over the west pacific coast (the closest one is ZOA1). Data importation and quality assurance are automated, although some manual correction of unusual data problems is still required. This year the volume of GPS data in raw format in the NCEDC storage facility has increased by $30 \%$ ( $\sim 525Mb/day$). This trend will continue with the installation of new sites (1Hz) and the conversion of the rest of the 15 sites of BARD.

As part of the activities funded by the USGS through the BARD network, the NCEDC has established an archive of the 7000+ survey-mode occupations collected by the USGS since 1992. The NCEDC continues to archive non-continuous survey GPS data. The initial dataset archived is the survey GPS data collected by the USGS Menlo Park for northern California and other locations. The NCEDC is the principal archive for this dataset. Significant quality control efforts were implemented by the NCEDC (Romanowicz et al., 1994) to ensure that the raw data, scanned site log sheets, and RINEX data are archived for each survey. All of the USGS MP GPS data has been transferred to the NCEDC, and virtually all of the data from 1992 to the present has been archived and is available for distribution. We are also archiving additional high-precision GPS data sets from northern California (mainly Parkfield measurements). Together with graduate students in the department who are now using the GAMIT software to process survey-mode data in the San Francisco Bay area, we are working to combine the survey-mode and C-GPS solutions into a self-consistent velocity field for northern California. The campaign velocity field computed from campaign measurements by UCB and USGS groups has been published by d'Alessio et al., (2005).

Data from five of our sites (HOPB, MHCB, CMBB, OHLN, YBHB) are sent to the National Geodetic Survey (NGS) in the framework of the CORS (Continuous Operating Reference Stations) project (http://www.ngs.noaa.gov/ CORS/). The data from these five sites are also distributed to the public through the CORS ftp site.

Berkeley Seismological Laboratory
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