SAO - San Andreas Geophysical Obs., Hollister, 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 SAO (SAOB)
In Operation 1988/01/28 00:00:00 - Present
Elevation: 317.2 meters
Instrumentation Broadband


Site is located at the San Andreas Geophysical Observatory in the Hollister Hills State Vehicle Recreation Area. The BSL first occupied this site in 1966, with a variety of geophysical instrumentation. The digital broadband sensors were installed in 1988.

SAO is a cooperative station with the Advanced National Seismic System.


Berkeley Digital Seismic Network (BK)
Bay Area Regional Deformation Network Network (BARD)


Jurassic-Cretaceous Gabilan Granite

Borehole Conditions

The vault is a buried steel culvert liner with a set of three isolation doors leading to the interior. The pier is poured concrete. The datalogger and supporting equipment are located in an air-conditioned structure approximately 50' away and connected via underground conduits. The seismometers are thermally insulated with 4" of polyurethane foam.

GPS Monument Description

Reinforced concrete monument

Seismic Station Pictures

View of SAO equipment building

View of SAO equipment building

View of SAO vault

View of SAO vault

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
BroadbandStreckeisen STS-1/E300 VBB Feedback SeismometerQ330HR-GFEBH?,HH?,LH?,VH?00
AccelerometerKinemetrics FBA ES-T Accel. GFE (4 g max 5 v/g)Q330HR-GFEHN?00
GPSTrimble NetRSAshtech Choke-RingSCIGN Tall-
SensorDataloggerSEED ChannelsLocation
OthersElectric Field Dipole (Pb-PbCl or Cu-CuS Anodes)Q4120BQ?,LQ?,UQ?,VQ?
ElectroMagnetics Inc. BF4 MagnetometerQ4120BT?,LT?,UT?,VT?
AuxiliaryBattery VoltageQ4120AE?
Internal TemperatureQ4120AK?

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
SAOB completeness last year
SAOB 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
SAOB multipath last year
SAOB multipath lifetime