NHFN Overview

The initial characterization period ended in 1997. During that period, the NHFN sensors provided signals to on-site, stand-alone Quanterra Q730 and RefTek 72A-07 dataloggers, and manual retrieval and download of data tapes was required. Also in that year, the long-term monitoring phase of the project began, involving the installation of 24-bit data acquisition and communication platforms and data telemetery to the BSL archives for a backbone of the initial NHFN stations.

Over the years, CalTrans has provided additional support for the upgrade of two non-backbone sites to backbone operational status and for the addition of several new sites to the monitoring back-bone. These expansion efforts are ongoing. Also since the transition to the long-term monitoring phase, the 5 stations of the MPBO project have been folded into the NHFN.

Of the 28 stations now considered part of the NHFN history, 14 of the stations are currently operational, with telemetered data streams flowing continuously into the BSL's BDSN processing stream with subsquent archival in the Northern California Earthquake Data Center (NCEDC) archive. These include the 5 MPBO sites. Nine of the original 28 are non-backbone stations that have not been upgraded to continuous telemtry. Though collection of data from these sites has been discontinued, their borehole sensor packages are still in place (having been grouted in), and efforts to find funding for upgrade of these sites with Quanterra Q4120, Q730 or Q330 dataloggers and continuous telemetry continues. The remaining 5 sites are in the process of being added to the NHFN backbone. Four of the sites have been drilled and instrumented and are awaiting installation of their electronics and infrastructures. Equipment has been purchased for the 1 remaining site, which is awaiting final land-use agreement from the Regional Parks district and drilling by CalTrans.

Installation/Instrumentation: The NHFN Sensor packages are generally installed at depths ranging between 100 and 200 m, the non-backbone non-operational Dumbarton bridge sites being exceptions with sensors at multiple depths (Table 3.5).

The five former MPBO sites that are now part of the NHFN have 3-component borehole geophone packages. Velocity measurements for the MPBO sites are provided by Mark Products L-22 2 Hz geophones (Table 3.6). All the remaining backbone and non-backbone NHFN sites have six-component borehole sensor packages. The six-component packages were designed and fabricated at LBNL's Geophysical Measurement Facility and have three channels of acceleration, provided by Wilcoxon 731A piezoelectric accelerometers, and three channels of velocity, provided by Oyo HS-1 4.5 Hz geophones.

The 0.1-400 Hz Wilcoxon accelerometers have lower self-noise than the geophones above about 25-30 Hz, and remain on scale and linear to 0.5 g. In tests performed in the Byerly vault at UC Berkeley, the Wilcoxon is considerably quieter than the FBA-23 at all periods, and is almost as quiet as the STS-2 between 1 and 50 Hz.

All 14 NHFN backbone sites have Quanterra dataloggers with continuous telemetry to the BSL. Signals from these stations are digitized at a variety of data rates up to 500 Hz at 24-bit resolution (Table 3.7). The dataloggers employ causal FIR filters at high data rates and acausal FIR filters at lower data rates.

Data Rates and Channels: Because of limitations in telemetry bandwidth and disk storage, 8 of the 9 (excluding VALB) six-component NHFN stations transmit one channel of geophone data continuously (i.e., their vertical geophone channels) and an additional 3 channels of triggered data in 90 sec. snippets. A Murdock, Hutt, and Halbert (MHH) event detection algorithm (Murdock and Hutt, 1983) is operated independently at each station on 500 sps data for trigger determinations. Because of they are quieter, the 3 triggered channels are taken from the Wilcoxon accelerometers when possible. However, there is a tendency for these powered sensors to fail and in such cases, geophone channels are substituted for the failed accelerometers. Station VALB also transmits data from only 4 channels; however, all channels are transmited continuously. Continuous data for all channels at reduced rates (20 and 1 sps) are also transmitted to and archived at the BSL. The five MPBO sites transmit their 3-component continuous geophone data streams at 100, 20 and 1 sps, which are also archived at BSL.

Table 3.5: Stations of the Hayward Fault Network. Each HFN station is listed with its station code, network id, location, operational dates, and site description. The latitude and longitude (in degrees) are given in the WGS84 reference frame. The elevation of the well head (in meters) is relative to the WGS84 reference ellipsoid. The overburden is given in meters. The start dates indicate either the upgrade or installation time. The abbreviations are: BB - Bay Bridge; BR - Briones Reserve; CMS - Cal Memorial Stadium; CB - Carquinez Bridge; DB - Dumbarton Bridge; MPBO - mini-Plate Boundary Observatory; RFS - Richmond Field Station; RSRB - Richmond-San Rafael Bridge; SF - San Francisco; SMB - San Mateo Bridge; SMC - St. Mary's College; and, YB - Yerba Buena. The * for station PINB indicates that this station name has been requested but has not yet been approved and may change. The * in the Date column indicates the stations that have recorded data from an earlier period of manually retrieved tapes, but that are currently off-line.
Code Net Latitude Longitude Elev (m) Over (m) Date Location
VALB BK 38.1215 -122.2753 -24 155.8 2005/11 - current Napa River Bridge
PETB BK 38.1189 -122.5011 -30 113 in progress Petaluma River Bridge
CRQB BK 38.05578 -122.22487 -25 38.4 1996/07 - current CB
HERB BK 38.01250 -122.26222 -25 217.9 2000/05 - current Hercules
PINB* BK 38.0113 -122.3653 tbd tbd in progress Point Pinole
BRIB BK 37.91886 -122.15179 219.7 108.8 1995/06 - current BR, Orinda
RFSB BK 37.91608 -122.33610 -27.3 91.4 1996/01 - current RFS, Richmond
CMSB BK 37.87195 -122.25168 94.7 167.6 1994/12 - current CMS, Berkeley
SMCB BK 37.83881 -122.11159 180.9 3.4 1997/12 - 2007/06 SMC, Moraga
SM2B BK 37.8387 -122.1102 200 150.9 2007/06 - current SMC, Moraga
SVIN BK 38.03325 -122.52638 -21 158.7 2003/08 - current MPBO, St. Vincent's school
OHLN BK 38.00742 -122.27371 -0 196.7 2001/07 - current MPBO, Ohlone Park
MHDL BK 37.84227 -122.49374 94 160.6 2006/05 - current MPBO, Marin Headlands
SBRN BK 37.68562 -122.41127 4 157.5 2001/08 - current MPBO, San Bruno Mtn.
OXMT BK 37.4994 -122.4243 209 194.2 2003/12 - current MPBO, Ox Mtn.
BBEB BK 37.82167 -122.32867 -31 150.0 2002/05 - current BB, Pier E23
E17B BK 37.82086 -122.33534   160.0 1995/08 - current * BB, Pier E17
E07B BK 37.81847 -122.34688 tbd 134.0 1996/02 - current * BB, Pier E7
YBIB BK 37.81420 -122.35923 -27.0 61.0 1997/12 - current * BB, Pier E2
YBAB BK 37.80940 -122.36450   3.0 1998/06 - current * BB, YB Anchorage
W05B BK 37.80100 -122.37370 tbd 36.3 1997/10 - current * BB, Pier W5
W02B BK 37.79120 -122.38525 -45 57.6 2003/06 - current BB, Pier W2
SFAB BK 37.78610 -122.3893   0.0 1998/06 - current * BB, SF Anchorage
RSRB BK 37.93575 -122.44648 -48.0 109.0 1997/06 - current * RSRB, Pier 34
RB2B BK 37.93 -122.41 tbd 133.8 2003/07 - current * RSRB, Pier 58
SM1B BK 37.59403 -122.23242   298.0 not recorded SMB, Pier 343
DB3B BK 37.51295 -122.10857   1.5 1994/09 - 1994/11 DB, Pier 44
          62.5 1994/09 - 1994/09  
          157.9 1994/07 - current *  
DB2B BK 37.50687 -122.11566     1994/07 - current * DB, Pier 27
          189.2 1992/07 - 1992/11  
DB1B BK 37.49947 -122.12755   0.0 1994/07 - 1994/09 DB, Pier 1
          1.5 1994/09 - 1994/09  
          71.6 1994/09 - 1994/09  
          228.0 1993/08 - current *  
CCH1 NC 37.7432 -122.0967 226   1995/05 - current Chabot
CGP1 NC 37.6454 -122.0114 340   1995/03 - current Garin Park
CSU1 NC 37.6430 -121.9402 499   1995/10 - current Sunol
CYD1 NC 37.5629 -122.0967 -23   2002/09 - current Coyote
CMW1 NC 37.5403 -121.8876 343   1995/06 - current Mill Creek

Table 3.6: Instrumentation of the HFN as of 06/30/2007. Every HFN downhole package consists of co-located 3-component geophones and accelerometers, with the exception of MPBO sites which have only 3-component geophones and are also collecting tensor strainmeter data. Six HFN sites (5 of the SHFN and 1 of the NHFN) also have dilatometers (Dilat.). Currently, 14 NHFN sites have Quanterra dataloggers with continuous telemetry to the BSL. The remaining backbone sites are either still being developed with support from Caltrans or are being upgraded to Quanterra dataloggers. The 5 SHFN sites have Nanometrics dataloggers with radio telemetry to the USGS. The orientation of the sensors (vertical - Z, horizontals - H1 and H2) are indicated where known or identified as "to be determined" (TBD).
Site Geophone Accelerometer Z H1 h2 datalogger Notes Telem.
VALB Oyo HS-1 Wilcoxon 731A TBD TBD TBD Q330   FR
PETB Oyo HS-1 Wilcoxon 731A TBD TBD TBD TBD   TBD
CRQB Oyo HS-1 Wilcoxon 731A -90 251 341 Q4120   FR
HERB Oyo HS-1 Wilcoxon 731A -90 TBD TBD Q4120   FR
PINB Oyo HS-1 Wilcoxon 731A TBD TBD TBD TBD   TBD
BRIB Oyo HS-1 Wilcoxon 731A -90 79 349 Q4120 Acc. failed, Dilat. FR
RFSB Oyo HS-1 Wilcoxon 731A -90 256 346 Q4120   FR
CMSB Oyo HS-1 Wilcoxon 731A -90 19 109 Q4120   FR
SMCB Oyo HS-1 Wilcoxon 731A -90 76 166 Q4120 Posthole FR
SM2B Oyo HS-1 Wilcoxon 731A TBD TBD TBD Q4120   FR
SVIN Mark L-22   -90 298 28 Q4120 Tensor. FR/Rad.
OHLN Mark L-22   -90 313 43 Q4120 Tensor. FR
MHDL Mark L-22   -90 TBD TBD Q4120 Tensor. FR
SBRN Mark L-22   -90 347 77 Q4120 Tensor. FR
OXMT Mark L-22   -90 163 253 Q4120 Tensor. FR
BBEB Oyo HS-1 Wilcoxon 731A -90 TBD TBD Q4120 Acc. failed Radio
E17B Oyo HS-1 Wilcoxon 731A -90 TBD TBD None at present    
E07B Oyo HS-1 Wilcoxon 731A -90 TBD TBD None at present    
YBIB Oyo HS-1 Wilcoxon 731A -90 257 347 None at present Z geop. failed FR/Rad.
YBAB Oyo HS-1 Wilcoxon 731A -90 TBD TBD None at present    
W05B Oyo HS-1 Wilcoxon 731A -90 TBD TBD None at present    
W02B Oyo HS-1 Wilcoxon 731A -90 TBD TBD Q4120   Radio
SFAB None LLNL S-6000 TBD TBD TBD None at present Posthole  
RSRB Oyo HS-1 Wilcoxon 731A -90 50 140 None at present 2 acc. failed FR
RB2B Oyo HS-1 Wilcoxon 731A -90 TBD TBD None at present 1 acc. failed  
SM1B Oyo HS-1 Wilcoxon 731A -90 TBD TBD None at present    
DB3B Oyo HS-1 Wilcoxon 731A -90 TBD TBD None at present Acc. failed  
DB2B Oyo HS-1 Wilcoxon 731A -90 TBD TBD None at present    
DB1B Oyo HS-1 Wilcoxon 731A -90 TBD TBD None at present Acc. failed  
CCH1 Oyo HS-1 Wilcoxon 731A -90 TBD TBD Nanometrics HRD24 Dilat. Radio
CGP1 Oyo HS-1 Wilcoxon 731A -90 TBD TBD Nanometrics HRD24 Dilat. Radio
CSU1 Oyo HS-1 Wilcoxon 731A -90 TBD TBD Nanometrics HRD24 Dilat. Radio
CYD1 Oyo HS-1 Wilcoxon 731A -90 TBD TBD Nanometrics HRD24 Dilat. Radio
CMW1 Oyo HS-1 Wilcoxon 731A -90 TBD TBD Nanometrics HRD24 Dilat. Radio


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