Abstract
In December 2003 a new CG5 gravimeter was tested at Hirogawara, where a gassy cold geyser is activated primarily by the evolution of carbon dioxide. The CG5 gravimeter has a new capability of raw data acquisition, which enables us to store the unprocessed 6 Hz data (gravity, tilt-x, tilt-y, and internal temperature) in memory. We detected a particular signal not in gravity but in tilt. Continuous gravity record at the geyser constrains the volume and/or the depth of the void, where fluid flow in/out accompanying the geyser activity. This result is of particular interest in field surveys of temporal gravity changes related to some environmental or geodynamical processes, where gravity variations are expected to occur in hours or shorter period. A combination of raw data recording and post-processing is believed to be effective in realizing high precision microgravity monitoring using the CG5 gravimeter.
