Deformation monitoring at Newberry
Ground deformation refers to any change in shape of the volcano, which can occur as a result of uplift or subsidence, stretching or contraction, or some combination of these types of movements. Levelling surveys measure vertical movements of the ground surface (uplift or subsidence). The GPS technique measures 3-dimensional movements and therefore is sensitive to both vertical and horizontal changes.
CVO conducted leveling surveys across Newberry Volcano in 1985, 1986, and 1994 for comparison to an initial USGS survey in 1931. The 1994 results indicated that the summit area of the volcano moved upward about 4 inches with respect to its base sometime between 1931 and 1994. Smaller surveys across the caldera floor in 1985 and 1986 showed that no uplift or subsidence occurred there during 1985-1994. The 1931 survey was less precise than the later ones, so the 1931-1994 uplift episode is uncertain. Lack of any measurable ground deformation in the summit area from 1985 to 1994, on the other hand, is well established.
Until 2011, Newberry Volcano was not continuously monitored for patterns of deformation. In 2002 and 2009, scientists deployed short-lived "campaign" GPS surveys that included measurements of ground postion at 27 locations (additional information about these campaign surveys can be found on the Earthquake Hazards Program website). When comparing the data between the two years, only background tectonic deformation was observed (all stations moving NNW at about 4 mm/yr (0.16 in/yr)). In 2011 the Cascades Volcano Observatory installed 8 real-time stations that have joint seismic and deformation (GPS) monitoring instruments. Recent results from these new "continuous" GPS stations are consistent with low rates of deformation measured between 2002 and 2009.