Stress Measurements - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 549

measurement and the directions of the maximum and minimum horizontal stresses are
entered. Subsequently, the maximum horizontal stresses can be smoothed by applying
a smoothing algorithm and represented as trajectories (Zang et al. 2012). In addition,
maps of arbitrary regions of interest can be defined and are available on demand.
The collected stress data are classified using a quality ranking. This ranking is intended
to guarantee reliability and global comparability of stress data ranging from A to E with
A being the highest quality. The quality ranking was introduced by Zoback & Zoback
(1989) and refined and extended by Sperner et al. (2003) and Heidbach et al. (2010).
As an example, Fig. 16.34 shows maps of central and northern Europe in which the
orientations of measured maximum horizontal stresses (left map) and smoothed maxi-
mum horizontal stresses (right map) are entered. In the left map the maximum horizon-
tal stresses are labeled with bars.
Figure 16.34 Stress map of central and northern Europe (Zang et al. 2012)
Signatures and colors indicate stress measurement method and tectonic faulting regime
differentiating normal dip-slip faulting (NF), reverse dip-slip faulting (RF) and strike-
slip faulting (SS). The kinematics of these faulting modes is described in Section 2.4.
The bar lengths are proportional to the quality of data. The maps only contain data
that are quality rated from A to C and thus being considered as reliable.