This week:PS #1 due today at beginning of classPS #2 is on the website, due next Tuesday (use student account to print) www.geology.cwu.edu/facstaff/huerta/g360/Reading: ch. 4- Strain (not 4.8) and Ch 5- Rheology of van der PluijmLab #3: Outcrop patterns, Ch 2 of RD&S

Terminology clarification:Differential stress: difference between maximum and minimum stress: = s1 –s3

Deviatoric stress: difference between mean stress and maximum stress (or minimum stress), which is the radius of the Mohr Circle: =(s1-s3)/2(See deveitis)

These equations hold for systems where we only deal with s1 and s3. This works in most real life cases, when the value of s2 does not affect the shear and normal stresses acting on faults and fractures.

Dilation

x

y

Principal Strain Axes

Finite strain vs. incremental strain

Coaxial strain

Incremental principal strain axes are the same throughout strain history

Non-coaxial strain

Incremental principal strain axes rotate throughout strain history

Quantifying strain

• Longitudinal• Volumetric• Angular

Strain States

(a) General strain

(b) Axially symmetric extension

(c) Axially symmetric shortening

(d) Plane strain

(e) Simple shortening

Strain on the map