Structural geology Structure Reconstruction of regional stress Ductile deformation Fold Foliation Lineation etc.. Brittle deformation Joint Tension gash Styloite Fault etc.. Fault Reconstruction of regional stress

Fault surfaces displaying the direction of slip lineation

Stereographic projection of a fault slip data set Slickenside lineation pitch pitch Fault plane Fault plane Lower hemisphere project

obtaining the orientation of principal stress axes Method of right dihedrons obtaining the orientation of principal stress axes from statistic method

STEREOGRAPHIC NET S’/S = f (inclination) S’/S = const.

Wuff net Schmidt net

Wuff net (equiangular) OPM isosceles triangle Schmidt net (equal-area) ON/OP = tan (p/4-i/2) ON = R tan (p/4-i/2) Schmidt net (equal-area) ON = OX, OX = (2)1/2 OH OH/OP = sin (p/4-i/2) ON = (2)1/2 R sin (p/4-i/2)

3D inversion of field data in fault tectonics Eigenvalues and eigenvectors of T give the orientation of principal stress axes (s1 , s2 and s3), as well as the shape ratio F of the stress ellipsoid (F = (s2-s3)/(s1-s3)). (e.g., Angelier, 1979, 1984, 1989, 1990)

Inversion result Field measured data Computed stress axes Theoretical fault shears (Angelier, 1990)

(Chang C. P., Unpubl.)

the seismic focal mechanism Example from the seismic focal mechanism F = (s2-s3)/(s1-s3) case 1 0  F  1 case 1 case 2  0 reverse and strike-slip case 2  1 normal and strike-slip (Kao and Jian, 2001)