Stress field

About: Stress field is a research topic. Over the lifetime, 11926 publications have been published within this topic receiving 226417 citations.

Cell division plane orientation based on tensile stress in Arabidopsis thaliana.

Abstract: Cell geometry has long been proposed to play a key role in the orientation of symmetric cell division planes. In particular, the recently proposed Besson–Dumais rule generalizes Errera’s rule and predicts that cells divide along one of the local minima of plane area. However, this rule has been tested only on tissues with rather local spherical shape and homogeneous growth. Here, we tested the application of the Besson–Dumais rule to the divisions occurring in the Arabidopsis shoot apex, which contains domains with anisotropic curvature and differential growth. We found that the Besson–Dumais rule works well in the central part of the apex, but fails to account for cell division planes in the saddle-shaped boundary region. Because curvature anisotropy and differential growth prescribe directional tensile stress in that region, we tested the putative contribution of anisotropic stress fields to cell division plane orientation at the shoot apex. To do so, we compared two division rules: geometrical (new plane along the shortest path) and mechanical (new plane along maximal tension). The mechanical division rule reproduced the enrichment of long planes observed in the boundary region. Experimental perturbation of mechanical stress pattern further supported a contribution of anisotropic tensile stress in division plane orientation. Importantly, simulations of tissues growing in an isotropic stress field, and dividing along maximal tension, provided division plane distributions comparable to those obtained with the geometrical rule. We thus propose that division plane orientation by tensile stress offers a general rule for symmetric cell division in plants.

Stress orientation profile to 3.5 km depth near the San Andreas Fault at Cajon Pass, California

Abstract: A detailed profile of the orientation of the apparent maximum horizontal compressive stress was constructed over the depth interval 1.75–3.46 km in the Cajon Pass drill hole, located 4.2 km from the San Andreas fault in southern California. The profile is based on the analysis of stress-induced well bore breakouts and consists of 32,616 orientation determinations at a basic sampling interval of ∼4 cm. The azimuth of the apparent maximum horizontal compressive stress around the borehole is 057° (s.d. = 19°). Depth-dependent variations in breakout azimuths, from a few degrees to as much as 100°, occur over depth intervals of several centimeters to hundreds of meters in the borehole, with wavelengths showing a self-similar distribution over a range of depth intervals. The variations in breakout orientation at depth seem to reflect stress fluctuations associated with active faults penetrated by the drill hole. Assuming linear elastic behavior, perturbations in stress magnitude and orientation were computed for predrilling slip on these faults. Fault stress drops limited to the ambient shear stress (i.e., up to total stress drop), along with occasional, local extreme stress drops and geometrical complications, can explain the variations in breakout orientations in the drill hole. The penetrative stress inhomogeneity may suggest that the average orientation of borehole breakouts in Cajon Pass, which indicates left-lateral shear on planes parallel to the San Andreas fault, may not be representative of the state of stress near the fault at depth in this region. Rather, the stress orientation profile indicates the superposition of numerous local stress perturbations on an average stress field which is characterized by an absence of appreciable right-lateral shear on planes parallel to the San Andreas. Combining these observations with the highly variable stress state in shallow boreholes in the western Mojave Desert, it is suggested that the heterogeneous stress field in this region, representing a spectrum of seismic events, may extend over substantial distances across and along the San Andreas fault zone. If the average measured breakout orientation in Cajon Pass is representative of the state of stress near the San Andreas in this region, then substantial left-lateral shear stress is resolved on planes parallel to the fault, in contradiction to the sense of its long-term motion. We use an elastic dislocation model to compute the net stress change near the Cajon Pass drill site since just prior to the large 1812 earthquake, taking into account coseismic slip in major earthquakes and aseismic accumulation of slip on the San Andreas and San Jacinto faults. The model suggests that the net change in fault-parallel shear stress during the current earthquake cycle in the Cajon Pass area is nearly negligible. The difference between the measured and computed results requires that additional left-lateral shear stress be superimposed on a generally fault-normal maximum horizontal compressive stress. The results suggest that during the great Fort Tejon earthquake of 1857, left-lateral shear stress parallel to the San Andreas fault in the region of Cajon Pass may have played a role in terminating the southeastward extent of the rupture propagation.

The use of eigenfunction expansions in the general solution of three-dimensional crack problems

Abstract: Eigenfunction expansion technique to analyze three dimensional crack and wedge problems, emphasizing stress field near straight edged crack

Rhinegraben and the Alpine system

Abstract: The regional stress field in and around the Rhinegraben rift system and in the adjacent parts of the Alps has been investigated by a series of “doorstopper” in situ stress determinations. This is a stress-relief method that measures rock strain by destressing the rock with an overcoring operation. The maximum component of horizontal compression was found to trend approximately northwest to north-northwest. The excess horizontal stress culminates in the central Alps, decreases abruptly at the northern margin of this mountain range, and has relatively low values in the foreland area of the Rhinegraben. Alpine folding and thrusting ceased in Pliocene time, but strong epeirogenic uplift continues today. While plate-tectonics compression relaxed, stresses caused by topographic effects and unloading increased within the rising mountain body. The directions of maximum horizontal compression are about normally oriented to the isobases of Holocene uplift. The measured excess stresses obviously are not sufficient for thrust progression, since the Alps are considerably consolidated. The Rhinegraben was formed as an extensional rift valley in mid-Eocene to early Miocene time. The remaining zone of weakness trends about parallel to the sinistral shear of the active regional stress field. Because of this, the rift belt has been remodeled into a shear zone; its slip rates are related to the lateral extension of the Alpine mountain body farther south. Deflected by two changes in the graben's axial trend, the neotectonic deformations of the individual graben segments demonstrate a varying interaction of shear with compression in one case or shear with extension in the others. Where active shearing ceases at the northern end of the graben, the shift of the South German block is transmitted directly to the northward adjacent Rhenish massif. This massif reacts by secondary movements along pre-existing discontinuities, by horizontal flexuring, and by seismic activity. Farther north, in the Lower Rhine embayment, the Holocene peri-Alpine stress regime causes extensional rifting and subsidence. Tectonic effects to be ascribed to the Holocene regional stress pattern may be recognized back to mid-Pliocene time. Before that, in early Pliocene to mid-Miocene time, tectonic deformations were controlled by different stress regimes. Plate-tectonics processes in the rigid sphere were complemented by plastic mass compensations within the asthenosphere. Mantle rise was an additional factor controlling the Tertiary process of extensional rifting.