Working with strainmeter data

The Plate Boundary Observatory (PBO), the geodetic component of the U.S. National Science Foundation–funded Earthscope program, includes 75 borehole and 6 laser strainmeters (http://pbo.unavco.org). The strainmeters are installed at several locations: on the Cascadia forearc in Washington state and on Vancouver Island, Canada; in arrays of two to nine instruments along the North American–Pacific plate boundary in California; at Mount St. Helens; and in Yellowstone National Park. For deformation signals seconds to weeks in duration, strainmeters have a resolution and a signal-to-noise ratio superior to those of seismometers and GPS. However, this high sensitivity can introduce nontectonic signals into strain data, presenting data interpretation challenges, especially for borehole strainmeters.