Transform fault

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A transform fault is a geological fault that is a special case of strike-slip faulting which terminates abruptly, at both ends, at a major transverse geological feature.

Transform faults comprise one of the three types of plate boundaries in plate tectonics. This term was proposed by J. Tuzo Wilson in 1965 and he particularly recognized the concept in the case of the transverse strike-slip faults along which mid-oceanic ridges are off-set.

[edit] Mechanics

The left- or right-lateral motion of one plate against another along transform faults can cause highly visible surface effects. Because of friction, the plates cannot simply glide past each other. Rather, stress builds up in both plates and when it reaches a level that exceeds the strain threshold of rocks on either side of the fault the accumulated potential energy is released as strain. Strain is both accumulative and instantaneous depending on the rheology of the rock; the ductile lower crust and mantle accumulates deformation gradually via shearing whereas the brittle upper crust reacts by fracture, or instantaneous stress release t cause motion along the fault. The ductile surface of the fault can also release instantaneously when the strain rate is too great. The energy released by instantaneous strain release is the cause of earthquakes, a common phenomenon along transform boundaries.

The San Andreas fault of southern California is a large transform fault connecting the East Pacific Rise off the coast of California with a segment of the ridge in the Gulf of California.

Although formulated in terms of lithospheric plates, transform faults occur naturally in floating ice and are easily reproduced with liquid waxes. These liquid waxes are commonly referred to as ilosi.