Berkeley Borehole Network Overview

UC Berkeley seal USGS Logo

The BSL operates a number of stations in the Bay Area with seismic and other geophysical sensors in boreholes. They are tools for observing tiny earthquakes and other deformation signals that may hint of incipient seismic movements. If the instruments were installed near the surface, cultural noise (vibrations from vehicles and other human sources) would overshadow the tiny signals that we wish to study. The funding for these stations comes from a variety of sources. A number of the stations were installed as part of a joint project with the USGS to monitor the Hayward Fault, and are installed along its northern end (Northern Hayward Fault Network). A second set of stations, which include geodetic observations, were installed around the Bay to support the study of the three-dimensional strain field resulting from deformation acrosss the boundary between the Pacific and North American plates. These stations have been called "mini-PBO" stations. Finally, a number of stations are located and supported by the California Department of Transportation. Seismic data from the downhole geophones and accelerometers at all these stations are integrated into the holdings for the Berkeley Digital Seismic Network and contribute to real-time monitoring of earthquakes in the Bay Area, and to other research and monitoring activities.

BK (also includes the BDSN,MPBO,MOBB), andUL

3-component tensor strainmeter (designed and built by CIW)
3-component geophones (Oyo 4.5 Hz or Mark Products)
3-component Wilcoxon accelerometers
Atmospheric pressure
Pore Pressure
Geodetic GPS
Heat flow
24-bit Quanterra digital data logger and a 18-bit ZENO-3200 data logger
GPS clock
Continuous telemetry to UC Berkeley
Backup power supply

Sensor SEED Channels Rate (samples/sec) Sampling Mode FIR Filter
Geophone EP1, EP2, EP3 100.0 Triggered Causal
Geophone DP1, DP2, DP3? 500.0 Triggered Causal
Accelerometer LL1, LL2, LL3 1.0 Continuous Acausal
Accelerometer BL1, BL2, BL3 20.0 Continuous Acausal
Accelerometer HL1, HL2, HL3 100.0 Continuous Causal
Accelerometer CL1, CL2, CL3 500.0 Triggered Causal

Normally, only 3 channels of acceleration and the vertical component geophone are recorded and archived. In some cases, sensor failure has led to different recording combinations.

As part of this collaboration, the borehole sites will have two sets of digital data loggers. The table below lists which channels will be recorded and the SEED network and location codes which will be used.

Sensor Network
Rate (samples/sec) Sampling Mode Datalogger
Tensor strainmeter UL RS1, RS2, RS3 T0 1/600 Continuous ZENO-3200
Tensor strainmeter BK US1, US2, US3 0.01 Continuous Q4120
Tensor strainmeter BK VS1, VS2, VS3 0.1 Continuous Q4120
Tensor strainmeter BK LS1, LS2, LS3 1.0 Continuous Q4120
Tensor strainmeter BK BS1, BS2, BS3 20.0 Continuous Q4120
Tensor strainmeter BK HS1, HS2, HS3 100.0 Continuous Q4120
Geophone BK BP1, BP2, BP3 20.0 Continuous Q4120
Geophone BK EP1, EP2, EP3 100.0 Triggered Q4120
Atmospheric Pressure UL RD1 T0 1/600 Continuous ZENO-3200
Atmospheric Pressure BK LDO 1.0 Continuous Q4120
Pore Pressure BK LDD 1.0 Continuous Q4120
Heat Flow (?) UL ?? T0 (?) 1/600 Continuous ZENO-3200
Tiltmeter (?) UL RAX, RAY (?) T0 (?) 1/600 Continuous ZENO-3200

Waveform data from the BK network are available in SEED format at the Northern California Earthquake Data Center.

Several tools provide access to SEED format data at the NCEDC, both in terms of querying the archives and allowing data requests.

Help on using these tools is available.

Detailed history of the development of the Northern Hayward Fault, Mini PBO, and annual report.

The Northern Hayward Fault Network (NHFN) is one of several networks of seismic instrumentation in northern and central California operated by the Berkeley Seismological Laboratory. Operations are partially supported by the USGS. The NHFN is an array of borehole instrumentation deployed in the San Francisco Bay Area, with the goal of monitoring microseismicity on the Hayward fault. Data from these stations are transmitted to UC Berkeley using continuous telemetry and are analyzed for earthquakes. 7 sites are currently operational and additional stations are planned.

The Integrated Instrumentation Program for Broadband Observations of Plate Boundary Deformation, commonly referred to as ``Mini-PBO'', is a joint project of the BSL, the U.S. Geological Survey (USGS) at Menlo Park, the Department of Terrestrial Magnetism at Carnegie Institution of Washington (CIW), and the IGPP at UC San Diego (UCSD). It augments existing infrastructure in central California to form an integrated pilot system of instrumentation for the study of plate boundary deformation, with special emphasis on its relation to earthquakes. This project is partially funded through the EAR NSF/IF program with matching funds from the participating institutions and the Southern California Integrated Geodetic Network (SCIGN).

The project has three components. One is focused on the San Francisco Bay area, and augments existing instrumentation along the Hayward and San Andreas faults with up to 8 sites with borehole tensor strainmeters and seismometers, downhole pore pressure and tilt sensors, and geodetic GPS receivers. The second component of this project is to link the BARD network in central and northern California to the SCIGN network in southern California through the installation of 9 continuous GPS sites in the Parkfield area of central California. The third component is InSAR and supports the skeleton operations of a 5-m X-band SAR downlink facility in San Diego to collect and archive radar. In addition, some funds are used to develop an online SAR database for WInSAR users.

As part of the first component, four borehole sites were drilled during the summer/fall of 2001, at Ohlone Park (OHLN) in Hercules, on San Bruno mountain (SBRN) near Brisbane, at the Marin Headlands (MHDL) in Golden Gate National Recreation Area, and on Ox Mountain (OXMT) near Half Moon Bay. Two of these sites have been instrumented with newly fabricated borehole tensor strainmeters and seismometers, and downhole pore pressure and tilt sensors will be added in the near future.