The 3-D Seismic Anatomy of a Strike Slip Fault System; The Great Glen Fault, Inner Moray Firth Basin, Scotland, U.K.

Abstract

Field studies observations of strike-slip zones (e.g. the San Andreas, Anatolian and Dead Sea fault systems) are limited by the extent of natural exposures. The geometry of strike-slip zones is difficult to unravel from seismic data due to the steep structural dips and tectonic complexity associated with such regimes. Additionally, the paucity of vintage seismic coverage and the non-unique solutions resulting from interpreting widely-spaced grids of 2D seismic lines led many workers to analogue modelling in an effort to better understand the structural development, growth and evolution of strike-slip zones. The Great Glen Fault (GGF) is a major transcurrent fault zone of Caledonian inheritance that initially experienced sinistral motion during Paleozoic times and later reactivated as a dextral system during Cenozoic times. The GGF fully transects onshore Scotland along a SSW-NNE striking valley; on its eastern margin, the GGF runs offshore into the North Sea Basin through the Inner Moray Firth Subbasin, transecting an ample sedimentary sequence that includes both syn-rift and post-rift sequences of Mesozoic age. A tightly spaced seismic interpretation over both a 320 sq. km 3D volume and a dense grid of regional 2D seismic lines has been carried out for various horizons of tectonic relevance, while four exploratory wells provide the stratigraphic control between the adjoining tectonic blocks. Two major fault families can be recognized throughout the area; a dominant SW-NE trend of Jurassic, syn-rift affinity, reactivated by strike-slip activity during Cenozoic times and a secondary, E-W extensional faults that are consistent with dextral transcurrent activity along the GGF. A series of N-S striking compressional folds (anticline-syncline train pairs) and a spectacular pop-up structure containing the Knockinnon oilfield at the relay between the two overlapping fault segments identified by the new interpretation resulted from Cenozoic transpression. This study demonstrates how the integration and interpretation of subsurface data provides the basis for unique and powerful new insights into the structural anatomy of strike-slip fault systems. Through the use of the well-constrained 3D seismic volume, the internal architecture of the GGF is revealed while structural aliasing is minimised from the interpretation. The results have implications for the nature of prospective trapping styles formed in strike-slip regimes in general and along the GGF in particular.

AAPG Datapages/Search and Discovery Article #90194 © 2014 International Conference & Exhibition, Istanbul, Turkey, September 14-17, 2014