Geodetic Measurement of Deformation Within the Papuan Fold and Thrust Belt

Abstract

The Papuan Fold and Thrust Belt (PFTB) is part of the New Guinea Highlands and comprises one of the active plate boundaries between the Australian Plate, which is moving north at ~70mm/year, and micro-plates adjacent to the Pacific Plate. It lies in central New Guinea which is amongst the most tectonically active regions on Earth. The PFTB, in particular, has very rugged and inaccessible terrain with extensive karst fields, gorges, high scarps, dense tropical vegetation and some of the highest precipitation rates in the world. Due to the location of the main PNG oil and gas fields, a dense network of geodetic control stations within the Eastern zone of the PFTB has been observed regularly by precision GPS since 2005. The primary purpose of the network has been to provide geodetic control for well head surveys, development of the PNG LNG project and estimation of transformation parameters between different geodetic and height datums used in the PNG Oilfields. Re-observation of the network over a period of eight years has enabled crustal deformation and geodetic strain rates to be measured within the eastern zone of PFTB for the first time. The network density and observation history have been sufficiently accurate to identify active thrusts within the PFTB and to quantify strain rates by space geodetic techniques. The foreland area, immediately southwest of the PFTB, is predominantly stable Australian Plate with 1.5 mm/year retardation resulting from locking of faults within the PFTB. Shortening across the PFTB is approximately 6 mm/year. Deformation within the PFTB appears to be highly localised. 3 mm/year shortening is observed between the Gobe operations camp and Gobe Airport and 4 mm/year between the Tari and Hides areas. These observations are consistent with localised areas of pinched casing in production wells interpreted to straddle active faults. In addition, it is common to find different borehole break-out orientations with depth in wells, suggesting different stress regimes on either side of active faults. Quantifying the strain-rates and location of these active faults is important in planning exploration wells and may be useful in assessing engineering risk for future pipelines and major projects.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015