GRAVITY STUDY OF THE OLD FAITHFUL GEYSER REGION, YELLOWSTONE NATIONAL PARK

The Yellowstone volcanic complex (YVC) has been associated with a stationary plume source but recent seismic and magnetotelluric studies have been interpreted to support either a deep or shallow plume source. Models created by these studies have shown that whatever the source, a plume is responsible for the caldera structure that encompasses most the Yellowstone region. Additionally, the active plume system is responsible for the famous geothermal features within the caldera including the famous geyser basins in the western portion of Yellowstone. The most famous of these geyser basins in the Upper Geyser basin which contains the most geysers in the world including Old Faithful. There have been numerous geological, geochemical and geophysical studies of the Old Faithful region but the most important study has been the 2017 controlled-source seismic study. This study showed that there was a higher velocity region northeast of Old Faithful and a lower velocity region southwest of it. The southwest region velocity structure was interpreted to be caused by a highly porous hydrothermal reservoir that was 10 to 60 meters below the surface. Thus, this region is thought to be the hydrothermal reservoir for the eruptions at Old Faithful. In order to better constraint the geometry, a detailed gravity study will be conducted. The gravity data will be collected on all available boardwalks and roads within the Upper Geyser basin. The analysis of these data will include wavelength filtering, derivatives and upward continuation. Two and three-dimensional density models will be constructed in order to determine the subsurface density structure and the sources of hydrothermal reservoirs.