Transform Fault

A transform fault is a strike-slip plate boundary where two plates slide horizontally past each other, most commonly the offsets that step a mid-ocean ridge axis sideways. J. Tuzo Wilson defined the concept in 1965, showing that slip occurs only on the active segment between two ridge crests, with motion opposite to the apparent ridge offset. Earthquakes are shallow and confined to that active reach. Beyond the ridge crests the trace continues as an inactive fracture zone. The San Andreas Fault is a continental transform; oceanic transforms such as the Romanche along the Mid-Atlantic Ridge can offset the axis by hundreds of kilometers.