Dilatant normal faulting in jointed cohesive rocks: a physical model study
Michael Kettermann1,Christoph von Hagke1,Heijn W. van Gent1,a,Christoph Grützner2,b,and Janos L. Urai1Michael Kettermann et al.Michael Kettermann1,Christoph von Hagke1,Heijn W. van Gent1,a,Christoph Grützner2,b,and Janos L. Urai1
Received: 10 Dec 2015 – Discussion started: 14 Jan 2016 – Revised: 22 Apr 2016 – Accepted: 16 May 2016 – Published: 27 May 2016
Abstract. Dilatant faults often form in rocks containing pre-existing joints, but the effects of joints on fault segment linkage and fracture connectivity are not well understood. We present an analogue modeling study using cohesive powder with pre-formed joint sets in the upper layer, varying the angle between joints and a rigid basement fault. We analyze interpreted map-view photographs at maximum displacement for damage zone width, number of connected joints, number of secondary fractures, degree of segmentation and area fraction of massively dilatant fractures. Particle imaging velocimetry provides insight into the deformation history of the experiments and illustrates the localization pattern of fault segments. Results show that with increasing angle between joint-set and basement-fault strike the number of secondary fractures and the number of connected joints increase, while the area fraction of massively dilatant fractures shows only a minor increase. Models without pre-existing joints show far lower area fractions of massively dilatant fractures while forming distinctly more secondary fractures.
We present an analogue modeling study on the interaction of pre-existing joints and normal faults using cohesive powder. We vary the angle between joints and a rigid basement fault and analyze interpreted map-view photographs at maximum displacement for various parameters and compare to nature. Results show a clear effect of increasing angle between joints and faults on fault geometry, fracture density and connectivity. These information can help interpreting fractured layers in the subsurface.
We present an analogue modeling study on the interaction of pre-existing joints and normal...