Abstract:
In April 2015, Ground Penetrating Radar (GPR) was used to characterise the shallow subsurface (0-5 m depth) of the western sinter slope, immediately adjacent to Old Faithful geyser and directly above an inferred, deep, geyser chamber. A series of time sequence images were collected between two eruptive events. Each set of time sequence GPR recordings consisted of four transects aligned at approximately 90° to each other, to enable coverage over the location of the inferred, deep, geyser chamber. Seven time sequence events were collected over a 48 minute interval to image changes in the near-surface, as well as pre- and post-eruptive cycles. No fractures were visible at the surface but the time sequence GPR images revealed a series of micro-fractures at 0-5 m depth that fill and drain repetitively, immediately after an eruption and prior to the main eruptive event. No large cavity was observed, but this could be present at depths greater than those possible to image using GPR.
