| During July 1990, members of the U.S. Geological Survey (USGS), David A. Johnston Cascades Volcano Observatory (CVO) in Vancouver, Washington, established a 23 station Global Positioning System (GPS) network near Mt. Shasta and Medicine Lake, California, using TI 4100 receivers. All of the stations were occupied for two consecutive days with each day's occupation consisting of 8 hours of observation. Stations Hat Creek and Quincy, both "Very Long Baseline Interferometer" (VLBI) stations, were used to fix station P501 which was occupied each day of the campaign and was used as a fiducial site. The GPS project was funded by the USGS Volcano Hazards and Geothermal Studies Program and contributes to a continuing effort to detect ground deformation related to magmatic or tectonic processes with the ultimate objective of assessing the potential for future eruptions in the Cascade Range. Crustal deformation can be a long term process; many decades may pass before any detectable changes can be measured. Therefore this report contains photographs and descriptions of the bench marks to provide a field guide for future reasearchers who may have a need to re-occupy the sites. -- Yamashita and Wieprecht, 1995 |
