The properties of critically connected faulted volumes: implications for the growth of fault systems



Duration - 01/07/2001 - 30/06/2003

Funding - Basic Research Grant from Enterprise Ireland, the Irish Government body for funding research

Basic Aims
Recent work (e.g. Sornette et al. 1990) suggests that fault systems attain critical states at which the geometrical properties of the system are those characteristic of a percolation network, in which faults form a connected network at a particular scale of observation. Interpretation of the scaling characteristics of earthquake systems (Sahimi et al. 1993), numerical models (e.g. Cowie 1998) and experimental models (e.g. Madden 1983, Liakopolou-Morris et al. 1994) lend support to this conjecture which has not, however, been tested on the geometrical characteristics, including the fault-related strain distributions, of well constrained natural datasets. The hypothesis predicts that at the critical state, active faults are located on the backbone of the percolation cluster and bound relatively rigid blocks. Since strain localisation should result in changes to the fault population scaling, fault systems are best studied in terms of both their spatial and size characteristics, i.e. in terms of fault-related strain distributions. At the percolation threshold there is a radical change of fault scaling properties and of the related flow and rheological properties of a faulted volume. The critical state can be achieved on scales from microscopic to that of tectonic plates and at different times.

The proposed behaviour of fault systems, in which fault system evolution is dominated by critical states in its geometrical evolution, has significant implications for the localisation of strain within fault systems, for the geometric evolution of sedimentary basins (most of which are controlled by faulting), and for the earthquake characteristics of currently active tectonic regimes. The purpose of this project is to establish quantitative descriptions of the geometric and scaling systematics of faults, that provide a basis for testing the percolation threshold hypothesis and for defining a new model for fault system development. Our research acknowledges the importance of strain distributions in fault localisation and growth, and will have at its core the analysis and modelling of displacement, and therefore strain, distributions within fault systems. Combined with a large library of 2-D and 3-D high quality fault datasets (from outcrop, satellite imagery and seismic data sources), this approach provides a basis for establishing the principal geometric and kinematic features of, and controls on, the progressive localisation of strain within evolving fault systems.


Contact: John Walsh
Tel: +353 1 716 2606
Email