Inferring stress from faulting: From early concepts to inverse methods

A revised crustal stress orientation database for Canada

“…A possible reason for this may be that the earthquakes, from which the S Hmax orientations are derived, occurred on a fault system that is not optimally oriented in the contemporary stress field. Following Heidbach et al (2010), FMS data always have the potential to inherit larger uncertainties on the derived S Hmax orientation than indicated by the C-quality assigned by default (Célérier et al, 2012). Another explanation is a low velocity anomaly, observed in shallow depth (b20 km) (Kao et al, 2013).…”

“…Due to the characteristics of a focal mechanism solution and the P-, B-, T-axes, the derived orientation of S Hmax is subject to an uncertainty of about 20-25°. Formal stress inversions of focal mechanisms (FMF) usually provide a better quality data (Arnold and Townend, 2007;Célérier et al, 2012;Dziewonski and Woodhouse, 1983;Gephart and Forsyth, 1984;Michael, 1987). Seismic data contributes further information about the stress field via the shear wave (SW) splitting method (e.g.…”

Volcano-tectonic interactions revealed by inversion of focal mechanisms: stress field insight around and beneath the Vatnajökull ice cap in Iceland

“…How can the presence of different types of focal mechanisms within the volume and the geometry of the active tectonic systems be explained? Paleostress analyses highlighted that the separation of a heterogeneous dataset into spatially and temporally homogeneous subsets is fundamental to avoid artefacts in stress solutions: such computed solutions can only represent a compromise between different homogeneous subsets and hence are inconsistent with the actual stress field (e.g., Célérier et al, 2012). Automatic and interactive separations to obtain homogeneous subsets have been performed for paleostresses (e.g., Armijo and Cisternas, 1978;Angelier, 1979;Angelier and Manoussis, 1980;Etchecopar et al, 1981;Etchecopar, 1984;Mercier and Carey-Gailhardis, 1989;Yamaji, 2000Yamaji, , 2003.…”

“…Two types of algorithm are used here: (1) a linear stress inversion, which minimizes the difference between sand τ implemented in the damped stress inversion (Michael, 1984(Michael, , 1987Hardebeck and Michael, 2006) and (2) a random stress search such as Etchecopar et al (1981) and Etchecopar (1984) implemented in the Fsa package (Célérier, 2013), which minimizes the angular α misfit between τ and s. For more details pertaining to the minimization criteria, the reader is referred to the review of Célérier et al (2012). The first algorithm is used to determine the regional stress field using all the dataset.…”

Application of paleostress analysis for the identification of potential instability precursors within the Benue Trough Nigeria

“…Their relative magnitudes are represented by the fourth parameter R. The two additional parameters of the full stress tensor arc the ratio of extreme principal stress magnitudes (σ 1 /σ 3 ) and the isotropic component of the stress tensor (the Mean stress), but these cannot be determined from fracture data only. The methods of paleostress inversion are numerical and currently involve the use of computer programmes to statistically analyse fracture data in order to characterize the stress field responsible for them (Etchecopar et al 1981;Angelier 1994;Ramsay and Lisle 2000;Delvaux and Sperner 2003;Célérier et al 2012). This study makes use of TENSOR™ program (Delvaux 1993;Delvaux et al 1997;Delvaux and Sperner 2003).…”