Introduction

The Bay Area Regional Deformation (BARD) network of continuously operating Global Positioning System (GPS) receivers monitors crustal deformation in the San Francisco Bay area (``Bay Area") and northern California (Murray et al., 1998). It is a cooperative effort of the BSL, the USGS, and several other academic, commercial, and governmental institutions. Started by the USGS in 1991 with 2 stations spanning the Hayward fault (King et al., 1995), BARD now comprises more than 70 permanent stations (Figure 7.1, Tables 7.1 and 7.2). The principal goals of the BARD network are: 1) to determine the distribution of deformation in northern California across the wide Pacific-North America plate boundary from the Sierras to the Farallon Islands; 2) to estimate three-dimensional interseismic strain accumulation along the San Andreas Fault (SAF) system in the Bay Area to assess seismic hazards; 3) to monitor hazardous faults and volcanoes for emergency response management; and 4) to provide infrastructure for geodetic data management and processing in northern California in support of related efforts within the surveying and other interested communities.

Figure 7.1: Operational BARD stations (dark triangles) in northern California (top) and in the San Francisco Bay area (bottom), including an 18-station network near the Long Valley Caldera (LVC) and a 14-station network near Parkfield (PKFD). In the oblique Mercator projection expected Pacific-North America relative plate motion is parallel to the horizontal. Circled stations use continuous real-time telemetry. The small black triangles near BRIB are the experimental L1 stations. Light triangles are PBO and Nucleus (previously existing continuous stations now part of PBO) stations operating in July 2005.

Among others, BARD includes 14 stations near Parkfield along the central San Andreas Fault, and 17 near the Long Valley caldera near Mammoth. The BSL maintains 22 stations [including 2 with equipment provided by Lawrence Livermore National Laboratory (LLNL) and UC Santa Cruz). Other stations are maintained by the USGS (Menlo Park and Cascade Volcano Observatory], LLNL, Stanford Linear Accelerator, UC Davis, UC Santa Cruz, Hat Creek Radio Observatory, U. Wisconsin, Haselbach Surveying Instruments, East Bay Municipal Utilities District, the City of Modesto, the National Geodetic Survey, Thales, Inc., and the Jet Propulsion Laboratory. Many of these stations are part of larger networks devoted to real-time navigation, orbit determination, and crustal deformation.

Table 7.1: Currently operating stations of the BARD GPS network maintained by the BSL and by the BSL/USGS/SCIGN in the Parkfield region. Receivers: A = Ashtech, T = Trimble. See Table 3.2 for telemetry codes and for BSL sites collocated with seismic stations. Data from other agencies retrieved or pushed by FTP or from the Web.

Code	Latitude	Longitude	Start	Receiver	Maint.	Telem.	Location
BRIB	37.91940	-122.15255	1993.58	A-Z12	BSL	FR	Briones Reservation, Orinda
CMBB	38.03418	-120.38604	1993.92	A-Z12	BSL	FR	Columbia College, Columbia
DIAB	37.87858	-121.91563	1998.33	A-Z12	BSL	FR	Mt. Diablo
FARB	37.69721	-123.00076	1994.00	A-Z12	BSL	R-FR/R	Farallon Island
HOPB	38.99518	-123.07472	1995.58	A-Z12	BSL	FR	Hopland Field Station, Hopland
LUTZ	37.28685	-121.86522	1996.33	A-Z12	BSL	FR	SCC Comm., Santa Clara
MHCB	37.34153	-121.64258	1996.33	A-Z12	BSL	FR	Lick Obs., Mt. Hamilton
MODB	41.90233	-120.30283	1999.83	A-Z12	BSL	NSN	Modoc Plateau
MOLA	37.94657	-122.41992	1993.75-2002.22	T-SSE	BSL		Pt. Molate, Richmond
MONB	37.49892	-121.87131	1998.50	A-Z12	BSL	FR	Monument Peak, Milpitas
MUSB	37.16994	-119.30935	1997.83	A-Z12	BSL	R-Mi-FR	Musick Mt.
OHLN	38.00742	-122.27371	2001.83	A-uZ	BSL	FR	Ohlone Park, Hercules
ORVB	39.55463	-121.50029	1996.83	A-Z12	BSL	FR	Oroville
OXMT	37.49936	-122.42432	2004.12	A-uZ	BSL	FR	Ox Mt., Half Moon Bay
PKDB	35.94524	-120.54155	1996.67	A-Z12	BSL	FR	Bear Valley Ranch, Parkfield
POTB	38.20258	-121.95560	1998.92-2005.12	A-Z12	BSL	FR	Potrero Hill, Fairfield
PTRB	37.99640	-123.01490	1998.58	A-Z12	BSL	R-FR	Point Reyes Lighthouse
SAOB	36.76530	-121.44718	1997.58	A-Z12	BSL	FR	San Andreas Obs., Hollister
SBRN	37.68622	-122.41044	2003.18	A-uZ	BSL	FR	San Bruno Mt., Brisbane
SODB	37.16640	-121.92552	1996.33	A-Z12	BSL	R-FR	Soda Springs, Los Gatos
SUTB	39.20584	-121.82060	1997.33	A-Z12	BSL	R-FR	Sutter Buttes
SVIN	38.03318	-122.52632	2003.89	A-uZ	BSL	R-FR	St. Vincents, San Rafael
TIBB	37.89087	-122.44760	1994.42	A-Z12	BSL	R	Tiburon
YBHB	41.73166	-122.71073	1996.75	A-Z12	BSL	FR	Yreka Blue Horn Mine, Yreka
CAND	35.93935	-120.43370	1999.33	A-Z12	USGS	R-FR	Cann, Parkfield
CARH	35.88838	-120.43082	2001.58	A-Z12	USGS	R-FR	Carr Hill 2, Parkfield
CARR	35.88835	-120.43084	1989.00-2003.31	A-Z12	JPL		Carr Hill, Parkfield
CRBT	35.79161	-120.75075	2001.67	A-Z12	USGS	R-FR	Camp Roberts, Parkfield
HOGS	35.86671	-120.47949	2001.50	A-Z12	USGS	R-FR	Hogs, Parkfield
HUNT	35.88081	-120.40238	2001.58	A-Z12	USGS	R-FR	Hunt, Parkfield
LAND	35.89979	-120.47328	1999.33	A-Z12	USGS	R-FR	Lang, Parkfield
LOWS	35.82871	-120.59428	2001.58	A-Z12	USGS	R-FR	Lowes, Parkfield
MASW	35.83260	-120.44306	2001.58	A-Z12	USGS	R-FR	Mason West, Parkfield
MIDA	35.92191	-120.45883	1999.75	A-Z12	USGS	R-FR	Mida, Parkfield
MNMC	35.96947	-120.43405	2001.58	A-Z12	USGS	R-FR	Mine Mt., Parkfield
POMM	35.91991	-120.47843	1999.75	A-Z12	USGS	R-FR	Pomm, Parkfield
RNCH	35.89999	-120.52482	2001.58	A-Z12	USGS	R-FR	Ranchita, Parkfield
TBLP	35.91741	-120.36034	2001.67	A-Z12	USGS	R-FR	Table, Parkfield

Table 7.2: Currently operating stations of the BARD GPS network maintained by other agencies and by the USGS Cascade Volcano Observatory (CVO) in the Long Valley caldera region. Other agencies include: EBMUD = East Bay Mun. Util. Dist., UCD = UC Davis, SU = Stanford Univ., UCSC = UC Santa Cruz, UWisc = U. of Wisconsin, City = City of Modesto (see also Table 2.1). Data from other agencies retrieved or pushed by FTP or from the Web.

Code	Latitude	Longitude	Start	Receiver	Maint.	Location
CHAB	37.72412	-122.11931	1992.00	A-Z12	USGS	Chabot, San Leandro
WINT	37.65264	-122.14056	1992.00	A-Z12	USGS	Winton, Hayward
EBMD	37.81501	-122.28380	1999.18	T-SSi	EBMUD	EBMUD, Oakland
QUIN	39.97455	-120.94443	1992.68	Rogue	JPL	Quincy
S300	37.66642	-121.55815	1998.48	T-SSi	LLNL	Site 300, Livermore
HCRO	40.81563	-121.46915	2003.50	T-SSi	HCRO	Hat Creek Radio Obs.
CHO1	39.43264	-121.66496	1999.50	A-Z12	NGS	Chico
CME1	40.44177	-124.39633	1995.74	A-Z12	NGS	Cape Mendocino
CMOD	37.64130	-121.99997	2000.76	T-SSi	City	Modesto
CNDR	37.89641	-121.27849	1999.27	A-Z12	NGS	Condor, Stockton
PBL1	37.85306	-122.41944	1995.50-2004.19	A-Z12	NGS	Point Blunt, Angel Island
PPT1	37.18167	-122.39333	1996.00	A-Z12	NGS	Pigeon Point
SLAC	37.41652	-122.20426	2002.34	Leica	SLAC	Stanford Linear Accel. Center
SUAA	37.42691	-122.17328	1994.30-2003.10	A-Z12	SU	Stanford University
THAL	37.35149	-121.93549	2003.00	A-uZ	Thales	Thales, Inc., Santa Clara
UCD1	38.53624	-121.75123	1996.38	T-SSi	UCD	UC Davis
UCSC	36.99279	-122.05219	2000.31-2002.67	T-SSi	UCSC	UC Santa Cruz
ZOA1	37.54305	-122.01594	2002.50	Novatel	FAA	Fremont
GR8V	36.39901	-120.41577	2003.04	T-5700	UWisc	San Andreas Creeping Segment
MEE1	36.18690	-120.75860	2003.02	T-5700	UWisc	San Andreas Creeping Segment
MEE2	36.18052	-120.76684	2003.03	T-5700	UWisc	San Andreas Creeping Segment
QCYN	36.16116	-121.13748	2003.05	T-5700	UWisc	San Andreas Creeping Segment
USBR	36.84257	-120.43567	2004.30	T-SSi	CVWD	Central Valley
CCID	36.73901	-120.35657	2004.30	T-NetRS	CVWD	Mendota, Central Valley
LNC1	38.84651	-121.35023	2003.51	A-Z12	NGS	Lincoln
PLSB	38.68530	-121.76150	2004.14	Leica	Haselbach	Woodland
SHJB	38.81418	-121.29606	2003.22	Leica	Haselbach	Rocklin
TMSB	38.57078	-121.54922	2003.22	Leica	Haselbach	West Sacramento
BALD	37.78330	-118.90130	1999.67	A-ZFX	CVO	Bald Mt., LVC
CA99	37.64460	-118.89670	1999.67	A-ZFX	CVO	Casa 1999, LVC
CASA	37.64464	-118.89666	1993.00	Rogue	JPL	Casa Diablo, LVC
DDMN	37.74430	-118.98120	1999.67	A-ZFX	CVO	Deadman Creek, LVC
DECH	38.05150	-119.09060	2001.58	A-ZFX	CVO	Dechambeau Ranch, LVC
HOTK	37.65860	-118.82130	2001.67	A-Z12	CVO	Hot Creek, LVC
JNPR	37.77170	-119.08470	1997.81	A-Z12	USGS	Juniper, LVC
KNOL	37.65912	-118.97917	1998.58	A-ZFX	CVO	Knolls, LVC
KRAC	37.71330	-118.88050	2001.67	A-Z12	CVO	Krakatoa-USGS, LVC
KRAK	37.71313	-118.88114	1994.73-2004.04	Rogue	JPL	Krakatoa, LVC
LINC	37.63719	-119.01729	1998.67	A-Z12	CVO	Lincoln, LVC
MINS	37.65376	-119.06090	1995.92	A-Z12	USGS	Minaret Summit, LVC
MWTP	37.64052	-118.94473	1998.58	A-ZFX	CVO	Mammoth Water Treat Plant, LVC
PMTN	37.83130	-119.05690	1999.67	A-Z12	CVO	Panorama Mt., LVC
RDOM	37.67707	-118.89794	1998.58	A-ZFX	CVO	Resurgent Dome, LVC
SAWC	37.68990	-118.95310	2000.65	A-ZFX	CVO	Saw, LVC
TILC	37.61890	-118.86280	2000.65	A-Z12	CVO	Tilla, LVC
WATC	37.66440	-118.65390	2001.67	A-Z12	CVO	Waterson, LVC

Between 1993 and 2001, the BSL acquired 29 Ashtech Z-12 and Micro-Z receivers from a variety of funding sources, including from federal (NSF and USGS), state (CLC), and private (EPRI) agencies. The network enhances continuous strain measurements in the Bay Area and includes several profiles between the Farallon Islands and the Sierra Nevada in order to better characterize the larger scale deformation field in northern California (Figure 7.1). Five sites have been equipped as part of the NSF-funded Mini-PBO project to establish collocated GPS, and borehole strainmeter and seismometer observatories in the Bay Area (see Chapter 8).

The number of continuous GPS stations in northern California is significantly increasing with over 250 new site installations planned by 2008 as part of the Plate Boundary Observatory (PBO) component of the NSF-funded Earthscope project. UNAVCO and researchers from BARD and the other regional networks, such as SCIGN, BARGEN, and PANGA, are funded by NSF to fold operation and maintenance of about 200 existing stations, which constitute the PBO Nucleus network, into the PBO array by 2008. Two BSL-maintained stations (SUTB and MUSB) are included in the PBO Nucleus network. The other BSL stations are either collocated with seismic instrumentation or are located near the San Andreas Fault where real-time processing of the GPS data for earthquake notification is a high priority. Another 23 northern California stations, including most of the Parkfield network, will be included in the PBO Nucleus, and we are working closely with UNAVCO to facilitate their transition to UNAVCO control.

Today, raw and RINEX data files from the BSL stations and the other stations run by BARD collaborators are archived at the BSL/USGS Northern California Earthquake Data Center (NCEDC) data archive maintained at the BSL (Romanowicz et al., 1994). The data are checked to verify their integrity, quality, completeness, and conformance to the RINEX standard, and are then made accessible, usually within 2 hours of collection, to all BARD participants and other members of the GPS community through Internet, both by anonymous FTP and by the World Wide Web (http://www.ncedc.org/bard/).

Many of the BARD sites are classified as CORS stations by the NGS, and are used as reference stations by the surveying community. We coordinate efforts with surveying community at meetings of the Northern California GPS Users Group and the California Spatial Reference Center. Data and ancillary information about BARD stations are also made compatible with standards set by the International GPS Service (IGS), which administers the global tracking network used to estimate precise orbits and has been instrumental in coordinating the efforts of other regional tracking networks. The NCEDC also retrieves data from other GPS archives, such as at SIO, JPL, and NGS, in order to provide a complete archive of all high-precision continuous GPS measurements collected in northern California.