OHLN - Ohlone Park, Hercules, CA, USA

We operate broadband and borehole stations under the network code BK. The Berkeley Digital Seismic Network (BDSN) is a regional network of very broadband and strong motion seismic stations designed to monitor regional seismic activity as well as provide high quality data. The Berkeley borehole stations have borehole geophones or other seismic sensors and may have other geophysical instrumentation.

BARD is our GPS network for monitoring crustal deformation across the Pacific-North America plate boundary and in the San Francisco Bay Area for earthquake hazard reduction studies and rapid earthquake emergency response assessment

Station Name OHLN (OHLN)
In Operation 2001/10/05 00:00:00 - Present
Elevation: -0.5 meters
Instrumentation Borehole


OHLN is one of five sites installed as a pilot test for the Plate Boundary Observatory, known informally as the Mini-PBO project. This site is known as SFOHL in the USGS Low Frequency Network and is located in Ohlone Park, in Hercules, CA.


Mini Plate Boundary Observatory Network (BK)
Bay Area Regional Deformation Network Network (BARD)
USGS Low Frequency Network (UL)


Sandstone, shale, siltstone, conglomerate, and breccia

Borehole Conditions

The OHLN borehole was the first of the MiniPBO sites to be drilled and was installed on 7/16/2001. The strainmeter is emplaced at a depth of 670.5 ft and the seismometer is at a depth of 645.5 ft. This figure shows the location of equipment in the borehole.

GPS Monument Description

1.25" pipe bolted into borehole casing

Seismic Station Pictures

Installation of strainmeter at OHLN<br>Courtesy of the USGS

Installation of strainmeter at OHLN
Courtesy of the USGS

Completed OHLN site, with GPS monument

Completed OHLN site, with GPS monument

GPS Station Timeseries

Time series processing at the BSL *

Last year Clean Clean & detrended Raw Raw & detrended
Lifetime Clean Clean & detrended Raw Raw & detrended
Text file (final results only) Clean Raw


GPS Station Pictures





Table of Seismic Instrumentation

SensorDataloggerSEED ChannelsLocation
GeophoneMark Products L-22 Horizontal GeophoneQ330-GFEEP?,LP?,SP?40
Mark Products L-22 Vertical GeophoneQ330-GFEEP?,LP?,SP?40
SensorDataloggerSEED ChannelsLocation
Paroscientific 8WD Digital Pressure MeterQ330-GFELD?40
Sacks 3-component Tensor StrainmeterQ330-GFEBS?,HS?,LS?40
Setra Systems Model 270 BarometerQEPLD?EP

GPS Instrumentation

GPSSeptentrio PolaRx5Ashtech Choke-RingSCIGN Tall-

Waveforms and associated metadata, and GPS data, are available at the Northern California Earthquake Data Center (NCEDC).

Waveform Data

GPS Data

Noise Analysis

View more noise plots

GPS Data Quality


Data completeness is defined both as "Completeness of observations" and "Cycle slips per observation". "Completeness of Obs." is the number of epochs in the final RINEX file normalized to the expected number. This percentage will go down if time is missing from the RINEX file. "Cycle slips per Obs." is the total number of detected cycle slip normalized to the total number of observations in the RINEX file. This number will increase as the receiver loses lock on satellites more frequently.

Previous Year
OHLN completeness last year
OHLN completeness lifetime


The effects of multipath on the data are estimated by parameters for L1 and L2 (MP1 and MP2 respectively); see Estey and Meertens (GPS Solutions, 1999) for derivation. The daily value is the RMS of MP1 and MP2 throughout the day and for all satellites. Higher values indicate a greater prevalence and/or strength of multipathing, i.e. objects on the ground are providing multiple reflection pathways from the satellite to antenna.

Previous Year
OHLN multipath last year
OHLN multipath lifetime

Signal-to-Noise Ratio

The Signal-to-Noise ratios are the mean values above the QC elevation mask for L1 and L2 respectively.

Previous Year
OHLN SNR last year
OHLN SNR lifetime