Brittle deformation

JointTension gashStyloiteFault etc..

Reconstruction of regional stress

Structural geology

Structure

Ductile deformation

FoldFoliationLineation etc.. Fault

Fault surfaces displaying the direction of slip lineation

Stereographic projection of a fault slip data set

Lower hemisphere project

Fault plane

Slickensidelineation

pitch

Fault plane

pitch

Method of right dihedrons

obtaining the orientationof principal stress axesfrom statistic method

S’/S = f (inclination)

STEREOGRAPHIC NET

S’/S = const.

Wuff net Schmidt net

Wuff net (equiangular)

OPM isosceles triangle

ON/OP = tan (/4-i/2)

ON = R tan (/4-i/2)

Schmidt net (equal-area)

ON = OX, OX = (2)1/2 OH

OH/OP = sin (/4-i/2)

ON = (2)1/2 R sin (/4-i/2)

3D inversion of field data in fault tectonics

Eigenvalues and eigenvectors of T give the orientation of principal stress axes (1 ,

2 and 3), as well as the shape ratio of the stress ellipsoid ( = (2-3)/(1-3)).

(e.g., Angelier, 1979, 1984, 1989, 1990)

Field measured data Computed stress axes Theoretical fault shears

Inversion result

(Angelier, 1990)

(Chang C. P., Unpubl.)

Example from the seismic focal mechanism

= (2-3)/(1-3)

0 reverse and strike-slip

1 normal and strike-slip

0 1

case 1

case 2

case 1

case 2

(Kao and Jian, 2001)