Experiments on strike-slip faulting and block rotation

Abstract

Analogue model experiments investigating strike-slip faulting in zones of distributed shear deformation show that fault orientations and fault evolution indicate modifications of the stress field with increasing bulk shear strain. Dextral bulk shear deformation at low strain is accommodated dominantly by synthetic strike-slip faults (Riedel shears). At higher strain, secondary antithetic and synthetic faults develop mostly between earlier formed major Riedel shears. Closely spaced parallel antithetic faults (cross faults) delimit domains that rotate about vertical axes with continuing shear deformation. Rotation of fault-bounded domains results in sigmoidal antithetic faults that have a dip-slip component and a dip direction that changes along strike. There is good agreement between models and natural examples of distributed shear zones where block rotations about vertical axes have been documented.