IMPROVED TERRAIN CORRECTION SOFTWARE FOR GRAVITY MODELING OF SALT DIAPIRISM IN CANYONLANDS NATIONAL PARK, UTAH

We employ gravity survey data, constrained by refraction seismic surveys, to model sediment fill and salt diapirism beneath Cyclone graben in Canyonlands National Park, Utah. Due to the small scale of the grabens (~200 m across Cyclone), and the sheer topography of the graben walls, precise terrain corrections to the gravity data are required. We develop and demonstrate a new implementation of terrain correction software to achieve the needed precision.

DEM data is treated as an array of right rectangular prisms of mass, and the terrain correction is calculated by summing the gravitational effect of each prism. An exact expression for the vertical component of acceleration due to a right rectangular prism is well known, but iterating this expression over every cell in a large DEM is computationally costly. We employ methods of approximating the gravitational effect of a prism, and establishing when the use of such approximations is appropriate. Our algorithm automatically detects regions where a coarser-resolution DEM would be allowable or a finer-resolution DEM would be useful.

We implement our algorithm as an extension to the widely used ArcGIS software. This approach not only allows us to utilize the data management, visualization and projection capabilities of the GIS, but also allows the use of geologic map layers to represent lateral variations in near surface density and the depth to which those density variations extend. Our approach is also applicable to 3-dimensional forward modeling of near-surface density variation using DEM elevations as upper bounds, effectively combining traditional partial Bouguer and terrain corrections into a forward modeling process.

Using data acquired over several field seasons, including 2013, we model both longitudinal and transverse gravity survey lines in Cyclone graben.

Session No. 21--Booth# 48

T27. Field-Based Research Experiences for Undergraduates (Posters)

Tuesday, 20 May 2014: 8:00 AM-5:00 PM

Ballroom B, C, D (Montana State University)

Geological Society of America Abstracts with Programs. Vol. 46, No. 5, p.70

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