PBO Borehole Strainmeters: Bridging the Gap Between Seismology and GPS Abstract


  • A key objective of the Plate Boundary Observatory, the geodetic component of Earthscope, is to capture the spatial and temporal deformation field across the western-US plate boundary. The observatory, being installed by UNAVCO, will consist of 103 borehole strainmeter/seismic sites, 880 GPS stations, 28 tiltmeters, and 5 laser strainmeters. Borehole strainmeters are designed to record deformation that lies between the spectral coverage of seismometers and GPS and are ideal for capturing strain transients that occur in periods of hours to months. Hence, they are being installed in arrays in targeted regions where they may capture short-term strain transients. As of 1st September 2007, 16 strainmeters have been installed in the Pacific Northwest, where strain transients associated with the 2005 and 2007 Cascadia ETS events were successfully recorded, 7 in Parkfield, in the transition zone between the creeping and locked section of the San Andreas Fault, 7 in Anza, in the aseismic section of the San Jacinto Fault, 4 in San Juan Bautista and 4 in central and southern Oregon. Three strainmeters of the first volcanic array were installed on Mt. St. Helens in July 2007. The combination of strainmeter, seismic, GPS and tilt measurements in these regions provides an unprecedented three-dimensional continuous dataset that spans the spectrum of plate boundary deformation. PBO borehole strainmeters record at 20-sps, 1-sps and 10-minute interval and the data are available in SEED format from the NCEDC and the IRIS DMC within minutes of download. Processed strainmeter data, produced by UNAVCO's Borehole Strainmeter Analysis Center are updated every 10 days and are available from the NCEDC and IRIS DMC in XML format. The processed data sets include tidal, atmospheric and borehole corrections plus data quality tags that flag non-tectonic signals. Users may also download raw strainmeter data via interactive plotting tools on the PBO web site or use SQUID, a GUI tool developed by PBO, to generate processed strainmeter data. A complete list of all strainmeter data products including metadata, borehole drawings and maintenance information is available at http://pboweb.unavco.org/strain_data.

publication date

  • 2007

presented at event