3D structure and kinematics of normal faults
A detailed 3D mapping of an exceptionally well exposed normal fault in Ptolemais Basin, NW Greece, has shown faults bifurcating both upwards and laterally, fault surfaces that are geometrically coherent but unconnected in 3D and relay zones that are breached at one location but intact at another. The role of the antithetic faults in transferring displacement across contractional and oblique relay zones has also been examined.
A quantitative 3D analysis of fault segmentation based on seismic reflection datasets has shown that (a) most relay zones are bifurcating structures, (b) oblique relay zones are less frequent, (c) dip relay zones are most commonly contractional, and (d) the mechanical heterogeneity of the faulted sequence and the influence of pre-existing structure are the underlying controls on the geometrical characteristics of relay zones in normal faults.
Where a significant number of relay zones are mapped on a single fault, a wide variety of relay zone geometries occurs, demonstrating that individual faults can comprise segments that are both bifurcating and unconnected in three dimensions.
Another analysis of the geometry of relay zones also suggests that the main controls on their aspect ratio are the strength of the sequence at the time of faulting and the underlying structure.
Bed-parallel slip in extensional settings
Identification and examination of bed-parallel slip (BPS) within an extensional fault system is very challenging in the absence of appropriate offset markers such as faults, veins, and dykes.
Excellent outcrop exposures of contemporaneous normal faulting and BPS in Ptolemais Basin (NW Greece) permit the examination of:
(a) the nature and origin of BPS,
(b) the role of BPS in the development of complex normal faults, and
bed-parallel slip in extensional basins is geometrically and/or kinematically associated with normal faulting.
the development of bed-parallel slip is kinematically associated with a broad range of fault-related deformation.
bed-parallel slip is common within multi-layered host rock sequences in extensional settings.
Fault-bend folding in extensional fault systems
Fault-bend folding refers to the folding of layered rocks in response to slip over a down-dip fault bend. Normal fault studies have investigated the geometry of hanging-wall rollover in relation to the shape of the fault bends but not the strain partitioning along them. A new quantitative model for the relationship between fault bend geometry and strain partitioning along normal faults highlights that fault throw can be subject to errors of up to 50 % for realistic fault bend geometries (up to 40°), with implications for across-fault juxtaposition and sealing, and assessments of hazard and earthquake slip.
Kinematics of basin-scale fault systems
The Porcupine Basin is a large under-explored sedimentary basin located offshore west of Ireland within the structurally complex European North Atlantic Margin. The nature and origin of multiple fault systems in the Porcupine Basin are explored based on analysis of large volumes of 2D and 3D seismic reflection data. Specifically, three distinct basin-wide phases of tectonically induced extensional faulting and a series of non-tectonic fault systems within specific stratigraphic intervals are recognized.
A metamorphic core complex (MCC) is an exposure of deep crust associated with extensional processes. Current understanding on MCCs is mainly derived form outcrop and geomorphic studies that only allow their exhumed part to be observed. A newly acquired 3D seismic reflection volume reveals a well-imaged MCC, the KP MCC, in the proximal northern South China Sea (SCS) rifted margin, permitting, for the first time, a detailed 3D examination of the MCC structure and its associated detachment fault. This study presents the 3D structure of the KP MCC, the geometry and kinematics of the associated KP detachment fault, and discusses the development and origin of the KP MCC.
Significance of different fault properties on earthquake characteristics
Physics-based earthquake simulators have been developed to overcome the relatively short duration and incompleteness of historical earthquake and paleoseismic records, respectively. These simulators have the potential to be a useful addition to seismic hazard assessment as they produce millions of synthetic earthquakes over thousands to millions of years using predefined fault geometries and slip rates. However, due to the sparsity of fault data and the computational expense of the modeling, it is common to simplify earthquake simulator input parameters.
During the Irish Research Council Government of Ireland Postdoctoral Fellowship, I employed an integrated multidisciplinary approach combining detailed structural characterization of a well-defined active normal fault in offshore New Zealand with physics-based earthquake simulations to examine of non-uniformly distributed fault slip rates and non-planar fault geometries on the resulting synthetic earthquake catalogues. This study demonstrated that details of the input fault geometries and slip rate distributions significantly affect the resulting synthetic earthquake catalogues from physics-based earthquake simulators, with substantial implications for seismic hazard applications.