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