What is "transtension"

Transtension is the state in which a rock mass or area of the Earth's crust experiences both extensive and transtensive shear. As such, transtensional regions are characterised by both extensional structures ( normal faults, grabens) and wrench structures ( strike-slip faults). In general, many tectonic regimes that were previously defined as simple strike-slip shear zones are actually transtensional. It is unlikely that a deforming body will experience 'pure' extension or 'pure' strike-slip.

Transtensional shear zones are characterized by the co-existence of different structures, related to both strike-slip shear and extension. End member structures include pure strike-slip faults and purely extensional ("normal") dip-slip faults. Faults which have components of both (termed 'oblique' slip faults) are abundant.