Fault linkage: Three‐dimensional mechanical interaction between echelon normal faults

Abstract

Abstract. Field observations of two overlapping normal faults and associated deformation document features common to many normal-fault relay zones: a topographic ramp between the fault segments, tapering slip on the faults as they enter the overlap zone, and associated fracturing, especially at the top of the ramp. These observations motivate numerical modeling of the development of a relay zone. A three-dimensional boundary element method numerical model, using simple fault-plane geometries, material properties, and boundary conditions, reproduces the principal characteristics of the observed fault scarps. The model, with overlapping, semicircular fault segments under orthogonal extension, produces a region of high Coulomb shear stress in the relay zone that would favor fault linkage at the center to upper relay ramp. If the fault height is increased, the magnitude of the stresses in the relay zone increases, but the position of the anticipated linkage does not change. The amount of fault overlap changes the magnitude of the Coulomb stress in the relay zone: the greatest potential for fault linkage occurs with the closest underlapping fault tips. Ultimately, the mechanical interaction between segments of a developing normal-fault system promote the development of connected, zigzagging fault scarps.

Analysis of the growth of strike-slip faults using effective medium theory

“…Due to high density of fractures, the mechanical properties of the rock mass at these locations are so altered that a new paradigm is required to analyze the conditions leading to the growth of faults by linkage of neighboring segments and by enlargement of fault rock into the adjacent inner damage zone. Thus, this premise separates the present study from those using single linkage structure whether in opening, closing, or shearing modes in pristine rock within the context of the LEFM (see for example, Segall and Pollard, 1980;Aydin, 1993, 1995;Crider and Pollard, 1998;and De Bremaecker and Ferris, 2004). In this regard, the underlying reasoning in our approach is similar to that of the damage concept of Lyakhovsky and Ben Zion (2008) if the fracture density is a proxy for the damage parameter in their model.…”

“…However, aside from a number of papers addressing 4 the stress state between neighboring faults and the type and orientation of the linkage structure (Segall and Pollard, 1980;Pollard and Segall, 1987;Aydin, 1993, 1995;Crider and Pollard, 1998;and De Bremaecker and Ferris, 2004), very little attention has been paid to quantification of the elastic parameters leading to the growth of the fault dimensions. To this end, there is only a handful of studies of the criteria for the linkage and coalescence of neighboring faults.…”

Elastic dislocation modeling of wrinkle ridges on Mars

“…The displacements and stresses are determined for a fault with a specified magnitude and sense of slip using elastic dislocation elements and the stress functions for an elastic half-space (Okada, 1992). This type of modeling has been used to reproduce well understood terrestrial faults (e.g., Stein and King, 1984;King et al, 1988aKing et al, , 1988bKing et al, , 1994King and Ellis, 1990;Bilham and King, 1989;Taboada et al, 1993;Crider and Pollard, 1998). Listric fault geometries have also been modeled using elastic dislocation modeling and the results compared to geodetic and surface scarp height data on terrestrial faults (Ward and Barrientos, 1986;Barrientos et al, 1987;Willsey et al, 2002).…”

Interpretation and analysis of planetary structures

“…The normal faults that define the graben transect a pre-existing ridge where non-vertical fault dip angles are demonstrated by widening of the graben (McGill,1971). Farther along strike, the grabens step to the left forming a relay ramp across an accommodation zone (Morley et al, 1990;Peacock and Sanderson, 1991;Davison, 1994;Crider and Pollard, 1998) with the inner faults changing polarity (dip direction) from one graben to the next.…”

“…Fault linkage is an essential process in the growth of fault populations (e.g., Crider and Pollard, 1998;Trudgill and Cartwright, 1994;Peacock, 2002). Fault populations on Mars display evidence for linkage via relay ramps (Fig.…”