A simple stress inversion of fault/slip data assuming Andersonian stress state

Abstract

Stress inversion from fault/slip data is an important modern technique for structural geologists. The parameter (or sigma) space may be reduced from five to three dimensions if an Andersonian stress state (having a vertical principal direction) is assumed. In such a case, associated fault/slip data can be displayed after some transformation on a stereonet. Homogeneous fault/slip data tend to lie in a great circle, while heterogeneous data lie in no less than two great circles. Visual appreciation thus becomes fairly easy, in particular, separation of the heterogeneous fault/slip data set into many homogeneous subsets. The unit vectors normal to the great circles are the solutions giving the controlling reduced stress vectors (v). Permitted solutions to a homogeneous set or subset are v and −v. The acceptability of each solution depends upon the fit between calculated and measured fault slip senses. Several examples of applications of this method are used for its validation. These examples also illustrate the potential value of the method in making a rough, simple and visual appreciation of fault/slip data under approximately Andersonian stress. We believe the method will have a broad applicability as Andersonian stress represents the ideal states for the various tectonic regimes.

Cenozoic Tectonic Deformation Along the Pontarlier Strike‐Slip Fault Zone (Swiss and French Jura Fold‐and‐Thrust Belt): Insights From Paleostress and Geomorphic Analyses

“…These methods are best applied to the sampled faults that have independently formed within a single or homogeneous stress tensor. A critical issue arises when these approaches are directly used to deal with very common heterogeneous data sets, that is, fault‐slip measurements originating from changes in the tectonic stress field (Nemcok & Lisle, 1995; Shan et al., 2004; Yamaji, 2000). The latter can lead to both newly formed faults with different orientations and reactivation of earlier ones (e.g., Bartholomew et al., 2002; Kim et al., 2001; Nixon et al., 2014).…”

“…Different approaches and computer programs have been developed for a fully automatic separation of different stress states from heterogeneous fault‐slip data without a preliminary sorting of the raw data (e.g., Etchecopar et al., 1981; Hardcastle & Hills, 1991; Melichar & Kernstockova, 2010; Nemcok & Lisle, 1995; Otsubo et al., 2006; Shan et al., 2004; Yamaji, 2000; Žalohar & Vrabec, 2007). Such approaches are not always reasonable and can produce spurious results (Liesa & Lisle, 2004).…”