Earth’s Plates. Stress-Strain Curves Elastic Limit.
Transcript of Earth’s Plates. Stress-Strain Curves Elastic Limit.
Earth’s Plates
Stress-Strain Curves
Elastic Limit
The Donath deformation apparatus
Confining pressure in nature is supplied by the pressure exerted by the weight of interconnected pore fluids
(hydrostatic pressure) and the overlying rockmass (lithostatic pressure). Here it is supplied by pumping up fluid pressure.
Calculating Axial Stress
What we know is the load or force that is being applied (F) and the cross sectional
area of the (A).
= F / A
We keep track of a pair of numbers:, e - axial strain and; - axial stress and plot
them in x,y space (respectively).
Effect of Temperature on Strength
Limestone become progressivley more ductile at higher confining presures
rocks, like the fence, will deform in different ways, depending uponthe properties of the rock and the nature of the applied stress
Dobras Falhas
Geologia Estrutural estudo da “arquitetura da Terra” ….examinação de rochas deformadas
DEFORMAÇÃO: mudanças em locação, orientação, forma, volume
Dúctil brittle (breaks)
from: Davis and Reynolds, 1996
Conceitos GeológicosTIPOS DE FALHAS
General Nature of Shear Fractures
• Shear fractures form from slip parallel to the face of the joint.
• They are about the same size and scale as joints, occur in
parallel sets, with spacings that are a function of the strength of the rock - as in regular joints.
• The surfaces are actually very small-displacement faults, that
are often adorned by slickenlines.
The apex of the acute angle points in the
direction of shortening
Slickenlines indicate movement direction.
Plumose Structure
CONCEITOS GEOLÓGICOSTIPOS DE FALHAS
TIPOS DE FALHASFalhas Normais e Inversas
Seção vertical de uma falha normal Zona de omissão indica movimentoextensional
Seção vertical de uma falha inversaÁrea de repetição indica movimentos compressivos
Falhas Transcorrentes
Movimentos senestral – bloco da esquerda avança
Movimentos destral – bloco da direita avança
CA Tectonic Elements
Offset Ditch, Hollister, CA - 1975
Offset Ditch, Hollister, CA - 1992
Sistema de falhas normais simétricos e assimétricos
Rotational
Nonrotational
Stress-Strain Curves
Elastic Limit
Stress-Strain
Fold Elements
Palmdale, CA Road Cut
Shear stress and strain
Photo credit: G. Mattioli
Steeply Dipping Beds,Pt. Arena, Ca
Medidas de campo