Analysis of fault networks and conjugate systems

Abstract

Faults networks exist over a range of scales and are important for understanding the brittle deformation and fluid transport processes within the Earth’s crust. Analysing fault networks by characterizing the organization of faulting within them; the distribution of numerous attributes (i.e. displacement, density, strain etc.); and assessing their connectivity is essential, as these provide information about a fault networks behaviour, growth and development. This thesis presents an analysis of various strike-slip and normal fault networks from north Devon, New Zealand and Alaska. The fault networks are interpreted using an array of datasets such as field observation, aerial photography, multibeam bathymetry, high resolution seismic profiles and 3-D seismic volumes. These are integrated with ArcGIS and robust methodologies are used to analyse each network.

Spatial mapping of various attributes indicates that there is much heterogeneity in the organization of faulting within fault networks. Different domains, defined by their deformation style and/or their kinematic behaviour, can develop within a fault network. Domino domains have a dominant fault set with larger displacements, which controls
systematic rotation of faults and bedding. Conjugate domains form when there are equal sizes and proportions of each fault set and show little or no rotation of bedding. Domains interact with one another and can form large damage zones to accommodate changes in strain. Strain accommodated by each domain can vary within a network and is either distributed across numerous faults or localized to a few large faults, however, the network will preserve strain compatibility between domains.

Fault interactions including splays, abutments and cross-cutting relationships are characterized by different displacement profiles. These can be divided into two groups based on their kinematics: antithetic interactions and synthetic interactions, which involve faults with the opposite and same motion senses, respectively. Fault development can be influenced by interactions with pre-existing structures. When earlier fault generations are reactivated they affect the orientation, displacement and distribution of new fault generations.

A topological analysis is developed to characterize fault networks and assess connectivity. This considers a network to comprise of nodes (I, Y and X) and branches (I-I, I-C and C-C) between nodes. The number and proportion of each topological component can be used to produce parameters that relate to the connectivity of a network, such as the number of connections per line or per branch. They can also provide information about the clustering and compartmentalization within a network.

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Identifiers

ORCID for J.M. Bull: orcid.org/0000-0003-3373-5807

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