Tarasov, BG & Randolph, MF 2007, 'Paradoxical Features of Primary Shear Fractures and General Faults', in Y Potvin (ed.), Deep Mining 2007: Proceedings of the Fourth International Seminar on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 165-182, https://doi.org/10.36487/ACG_repo/711_Tarasov
(https://papers.acg.uwa.edu.au/p/711_Tarasov/)
Abstract: This paper shows that hard rocks exhibit specific properties at high confining pressure that distinguish them 
markedly from common rock behaviour: they become extremely brittle and lose shear resistance within a 
certain range of shear rupture displacement. The combination of these two features results in increasing 
instability with depth and makes rupture abnormally violent, both of which are well established 
experimentally from studies of earthquakes and rock bursts at high stress levels. The behaviour is caused by 
the intrinsic nature of the fault structure, which is an echelon of blocks operating as hinges, essentially 
eliminating friction at high confining pressure of a certain displacement range. The paper demonstrates that, 
while the same structure may be found at different scale in primary fractures and general faults, significantly 
different mechanisms are responsible for the formation of the structure in each case. A new approach is 
proposed for understanding fault segmentation and the role of junctions in fault propagation. It is argued 
that segmentation is a result of advanced triggering of new fractures that propagate both towards the 
current fracture and in the opposite direction. This mechanism triples the fault propagation speed. Junctions 
formed at the meeting of the approaching segments help to accommodate the fault displacement and can 
significantly decrease the fault strength - thus contradicting the general belief that junctions represent 
strength barriers impeding the fault motion. The improved understanding of the fracture process is important 
for better prediction and mitigation of dynamic events such as earthquakes and rock bursts.