The evolution of the damage zone with fault growth in sandstone and its multiscale characteristics

Abstract

We document the formation and evolution of the damage zones associated with strike‐slip faults in porous sandstone, through detailed field and statistical studies of faults of increasing slip magnitudes. The faults initiate as sheared joints with discontinuous damage zone located primarily at fault tips and fault surface irregularities. With increasing slip, the damage zone develops by progressive fracture infilling and is organized into two components with different characteristics. The first of these components is the inner damage zone flanking the fault core with a high fracture frequency and a thickness scaling with fault slip. It contributes to the progressive widening of the fault core with increasing deformation. The second of these components is the outer damage zone with a larger and more variable thickness and a lower fracture frequency than the inner zone. The origin and evolution of the inner and outer damage zones are closely related to the history of fault development, as presented in a new conceptual model for damage zone evolution with fault growth. The statistical properties of the fault networks, determined by scan line surveys, evolve with fault growth. This is attributed to the progressive saturation of the fault networks. Well‐developed fault networks have multifractal properties with important consequences in forecasting and characterizing faults from limited data sets. The conceptual model and statistical data presented here may be used as predictive tools to better estimate the geometrical and statistical properties of the damage zones associated with large faults with remotely resolvable slip magnitude in the subsurface.

Permeability of a fault zone crosscutting a sequence of sandstones and shales and its influence on hydraulic head distribution in the Chatsworth Formation, California, USA

“…The widths of the stepovers, which are expressed by a negative relief, define approximately the fault zone width varying from 30 to 150 m at the surface. These observations are consistent with the inferred dominant left-lateral slip component across the fault zone and its growth by the linkage of neighboring segments similar to those described by other authors at various locations (Cartwright et al 1995;de Joussineau and Aydin 2007;Aydin and Berryman 2010).…”

Influence of Landscape Coverage on Measuring Spatial and Length Properties of Rock Fracture Networks: Insights from Numerical Simulation

“…Such vegetation-induced biases may also be a factor that contributes to the observed inconsistency of power law scaling of fracture lengths over different length scales (Nicol et al 1996;de Joussineau and Aydin 2007;Davy et al 2010). Actually we can also see from Fig.…”

From slow to fast faulting: recent challenges in earthquake fault mechanics

“…Cowie & Scholtz [26] observed from field data that the size of the breakdown zone scales with the length of the fault, therefore that energy loss per unit fault area should also scale with fault length. Additional laboratory experiments [23,27] and field studies on natural faults [20,[28][29][30][31] also indicated that the width of damage zone increases with fracture length. As pointed out by Nielsen et al [32,33], this offers an interpretation for the apparent discrepancy between fracture energy in large earthquakes (estimated from seismology), and fracture energy resulting from frictional weakening under seismic slip conditions (measured in laboratory experiments).…”