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TRANSPRESSION AND TRANSTENSION

In dextral faults, right bends are extensional while left bends contractional. In contrast, in case of sinistral faults, the

right bends are contractional while left bends extensional. If the bend and sense are of the same sense, it gives rise to transtension, if the bend and sense are opposed, the transpression zones are produced. Thus there are two bends releasing and restraining bends, those that cause extension and those which cause contraction.

This geometry can be seen at a variety of scales.

It may originate from:

  • linkage of en echelon structures.
  • previous anisotropy at an angle to the block movement vector.
  • change in kinematics.

if large enough scale (lithospheric) then can a locking bend is transpressive and a releasing bend is transtensive. Major strike-slip zones often characterized by significant geometric and kinematic change along strike

Transpression and transtension and flower structures can be
defined in cross section perspective:
  • faults steepen with depth.
  • faults are predominantly strike-slip, but with a consistent dip-slip component.
  • steep portion often not well imaged seismically.
  • consideration of 3-d deformational balancing