DOI: 10.5066/p9gq000j
title: Results of repeated leveling surveys near the Three Sisters volcanic center, central Oregon, 2002-2008

description: This Data Release includes results of repeated leveling surveys each summer from 2002 to 2006 and in 2008 along two short traverses in the Three Sisters Wilderness Area, central Oregon Cascade Range. A data dictionary explains the file format and contents. The dataset will be updated if new measurements are collected, which is unlikely unless there is a significant change in the rate or pattern of activity observed to date. This Data Release includes results of repeated leveling surveys each summer from 2002 to 2006 and in 2008 along two short traverses in the Three Sisters Wilderness, central Oregon Cascade Range. The surveys were part of an undertaking by the USGS Cascades Volcano Observatory to monitor an episode of surface inflation centered about 5 km west of the summit of South Sister volcano, first detected with interferometric synthetic aperture radar (InSAR) in 2001 (Wicks and others, 2002). In addition to leveling and InSAR observations, GPS data were collected from three continuous GPS stations, and from summertime campaign GPS and semipermanent GPS (SPGPS) surveys (Dzurisin and others, 2006; 2009; 2017). Leveling surveys followed standards and procedures for first-order, class II surveys (Vanicek and others, 1980; Federal Geodetic Control Committee, 1984). Corrections for rod scale, rod temperature, level collimation, and refraction were applied to observed elevation differences as specified by Balazs and Young (1982). Elevation differences between survey marks with an average spacing of 560 meters were measured on traverses along the James Creek and Separation Creek Trails that intersect at mark P, within 1 km of the center of uplift as shown by InSAR. The north-south traverse along James Creek Trail is 13.6 km long and the east-west traverse along Separation Creek Trail is 3.2 km long (stadia distances). Additional details of survey mark installation, equipment used, and procedures were provided by Dzurisin and others (2006). References Balazs, E.I., and Young, G.M. (1982), Corrections applied by the National Geodetic Survey to precise leveling observations, NOAA Technical Memorandum NOS NGS 34, 12 p. Dzurisin, D., Lisowski, M., Wicks, C.W., Poland, M.P., and Endo, E.T. (2006), Geodetic observations and modeling of magmatic inflation at the Three Sisters volcanic center, central Oregon Cascade Range, USA, Journal of Volcanology and Geothermal Research, v. 150, no. 1-3, p. 35-54, doi:10.1016/j.jvolgeores.2005.07.011. Dzurisin, D., Lisowski, M., and Wicks, C.W. (2009), Continuing inflation at Three Sisters volcanic center, central Oregon Cascade Range, USA, from GPS, leveling, and InSAR observations, Bulletin of Volcanology, v. 71, no. 10, p. 1091-1110, doi:10.1007/s00445?009?0296?4. Dzurisin, D., Lisowski, M., and Wicks, C.W. (2017), Semipermanent GPS (SPGPS) as a volcano monitoring tool: Rationale, method, and applications, Journal of Volcanology and Geothermal Research, v. 344, p. 40-51, doi: 10.1016/j.jvolgeores.2017.03.007. Federal Geodetic Control Committee (1984), Bossler, J.D. (chairman), Standards and specifications for geodetic control networks, National Oceanic and Atmospheric Administration, Rockville, Maryland. Langbein, J. (2008). Noise in GPS displacement measurements from Southern California and Southern Nevada; Journal of Geophysical Research, 113 B05405, https://doi.org/10.1029/2007JB005247. Langbein, J., and Johnson, H. (1997). Correlated errors in geodetic time series-Implications for time-dependent deformation: Journal of Geophysical Research, v. 102, no. B1, p. 591-603, https://doi.org/10.1029/96JB02945. Pelton, J.R., and Smith, R.B. (1982). Contemporary vertical surface displacements in Yellowstone National Park: Journal of Geophysical Research, v. 87, p. 2745-2761, https://doi.org/10.1029/JB087iB04p02745. Vanicek, P., Castle, R.O., and Balazs, E.I. (1980), Geodetic leveling and its applications. Reviews of Geophysics, v. 18, p. 505-524. Wicks, C.W., Dzurisin, D., Ingebritsen, S., Thatcher, W., Lu, Z., and Iverson, J. (2002), Magmatic activity beneath the quiescent Three Sisters volcanic center, central Oregon Cascade Range, USA, Geophysical Research Letters, 29(7), p. 1122, doi:10.1029/2001GL014205. Wyatt, F.W. (1989), Displacement of surface monuments-Vertical motion, Journal of Geophysical Research, v. 94, p. 1655-1664.