Effects of Structural and Stress Anisotropy on Velocity of Low-Amplitude Compression Waves Propagating Along Principal Stress Directions in Dry Sand.

1984 ◽  
Author(s):  
S. H. H. Lee ◽  
H. Y. F. Chu ◽  
K. H. Stokoe ◽  
II
Keyword(s):  
Principal Stress ◽  
Compression Waves ◽  
Stress Anisotropy ◽  
Stress Directions ◽  
Amplitude Compression ◽  
Dry Sand ◽  
Low Amplitude

Rotation of the principal stress directions due to earthquake faulting and its seismological implications

1995 ◽  
Vol 85 (5) ◽  
pp. 1513-1517
Author(s):  
Z.-M. Yin ◽  
G. C. Rogers
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Principal Stress ◽  
Stress Drop ◽  
Rotation Angle ◽  
Overburden Pressure ◽  
Rupture Area ◽  
Earthquake Faulting ◽  
Stress Directions ◽  
Before And After

Abstract Earthquake faulting results in stress drop over the rupture area. Because the stress drop is only in the shear stress and there is no or little stress drop in the normal stress on the fault, the principal stress directions must rotate to adapt such a change of the state of stress. Using two constraints, i.e., the normal stress on the fault and the vertical stress (the overburden pressure), which do not change before and after the earthquake, we derive simple expressions for the rotation angle in the σ1 axis. For a dip-slip earthquake, the rotation angle is only a function of the stress-drop ratio (defined as the ratio of the stress drop to the initial shear stress) and the angle between the σ1 axis and the fault plane, but for a strike-slip earthquake the rotation angle is also a function of the stress ratio. Depending on the faulting regimes, the σ1 axis can either rotate toward the direction of fault normal or rotate away from the direction of fault normal. The rotation of the stress field has several important seismological implications. It may play a significant role in the generation of heterogeneous stresses and in the occurrence and distribution of aftershocks. The rotation angle can be used to estimate the stress-drop ratio, which has been a long-lasting topic of debate in seismology.

Stress Path Tests with Controlled Rotation of Principal Stress Directions

2009 ◽  
pp. 516-516-25 ◽  
Author(s):  
JRF Arthur ◽  
S Bekenstein ◽  
JT Germaine ◽  
CC Ladd
Keyword(s):  
Principal Stress ◽  
Stress Path ◽  
Stress Directions

Design of a defence hole system for a shear-loaded plate

2003 ◽  
Vol 38 (6) ◽  
pp. 507-517 ◽  
Author(s):  
S. N Akour ◽  
J. F Nayfeh ◽  
D. W Nicholson
Keyword(s):  
Finite Element Analysis ◽  
Principal Stress ◽  
Pure Shear ◽  
Optimization Method ◽  
Optimum Size ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Search Optimization ◽  
Stress Directions ◽  
Circular Holes

Stress concentrations associated with circular holes in pure shear-loaded plates can be reduced by up to 13.5 per cent by introducing elliptical auxiliary holes along the principal stress directions. These holes are introduced in the areas of low stresses near the main circular hole in order to smooth the principal stress trajectories. A systematic study based on univariate search optimization method is undertaken by using finite element analysis (FEA) to determine the optimum size and location for an auxiliary defence hole system. The results are validated using RGB (red-green-blue) photoelasticity.

Analytical solution for tunnels not aligned with geostatic principal stress directions

2018 ◽  
Vol 82 ◽  
pp. 394-405 ◽  
Author(s):  
Osvaldo P.M. Vitali ◽  
Tarcisio B. Celestino ◽  
Antonio Bobet
Keyword(s):  
Analytical Solution ◽  
Principal Stress ◽  
Stress Directions

scholarly journals Inferring rheology and geometry of subsurface structures by adjoint-based inversion of principal stress directions

2020 ◽  
Vol 223 (2) ◽  
pp. 851-861 ◽  
Author(s):  
G S Reuber ◽  
L Holbach ◽  
A A Popov ◽  
M Hanke ◽  
B J P Kaus
Keyword(s):  
Principal Stress ◽  
Seismic Anisotropy ◽  
Stokes Equations ◽  
Adjoint Equations ◽  
Rheological Parameters ◽  
Complementary Method ◽  
Subsurface Structures ◽  
Model Domain ◽  
Stress Directions ◽  
Surface Observations

SUMMARY Imaging subsurface structures, such as salt domes, magma reservoirs or subducting plates, is a major challenge in geophysics. Seismic imaging methods are, so far, the most precise methods to open a window into the Earth. However, the methods may not yield the exact depth or size of the imaged feature and may become distorted by phenomena such as seismic anisotropy, fluid flow, or compositional variations. A useful complementary method is therefore to simulate the mechanical behaviour of rocks on large timescales, and compare model predictions with observations. Recent studies have used the (non-linear) Stokes equations and geometries from seismic studies in combination with an adjoint-based approach to invert for rheological parameters that are consistent with surface observations such as GPS velocities. Nevertheless, it would be useful to use other surface observations, such as principal stress directions, as constraints as well. Here, we derive the adjoint formulation for the case that principal stress directions are used as observables with respect to rheological parameters. Both an algebraic and a discretized derivation of the adjoint equations are described. This thus enables the usage of two data fields - surface velocities and stress directions - as a misfit for the inversion. We test the performance of the inversion for principal stress directions on simplified 3-D test cases. Finally, we demonstrate how the adjoint approach can be used to compute 3-D geodynamic sensitivity kernels, which highlight the areas in the model domain that have the largest impact on the misfit value of a particular point. This provides a simple, yet powerful, way to visualize which parts of the model domain are of key importance if changing rheological constants.

Analysis of Fracturing in Precambrian Volcanics North of Madoc, Ontario

1971 ◽  
Vol 8 (10) ◽  
pp. 1302-1313 ◽  
Author(s):  
P.-Y. Robin ◽  
J. B. Currie
Keyword(s):  
Principal Stress ◽  
Rock Material ◽  
Structural Element ◽  
Metavolcanic Rocks ◽  
Stress Directions ◽  
Specific Fracture

This paper presents a study of joints and other systematic fractures in Precambrian metavolcanic rocks. Although the mechanism that created the complex array of joints is not clear, one can deduce that they served as pre-existing planes of weakness during a later period of deformation in which slip occurred along both joints and systematic fractures. One consequence of this movement was an adjustment of rock material at the junction of intersecting fractures. An 'adjustment surface' was created at specific fracture intersections by movement of adjacent joint blocks toward one another. This 'adjustment feature' is a structural element, which can be utilized in reconstructing the principal stress directions of the later period of deformation.

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