Tectonic interpretation of the connectivity of a multiscale fracture system in limestone

Abstract

This paper studies the statistics and tectonism of a multiscale natural fracture system in limestone. The fracture network exhibits a self-similar characteristic with a correlation between its power law length exponent a and fractal dimension D, i.e., a ≈ D + 1. Contradicting the scale-invariant connectivity of idealized self-similar systems, the percolation state of trace patterns mapped at different scales and localities of the study area varies significantly, from well to poorly connected. A tectonic interpretation based on a polyphase fracture network evolution history is proposed to explain this discrepancy. We present data to suggest that the driving force for fracture formation may be dissipated at the end of a tectonic event when the system becomes connected. However, the "effective" connectivity can successively be reduced by cementation of early fractures and reestablished by subsequent cracking, rendering a variable "apparent" connectivity that can be significantly above the percolation threshold.