Origin, Evolution, Seismicity, and Models of Oceanic and Continental Transform Boundaries

This chapter focuses on comparing major geological-geophysical characteristics and origins of oceanic and continental transforms with an emphasis on numerical modeling studies. Transform boundaries on Earth can be subdivided in two major classes, continental and oceanic, characterized by markedly different tectonic position, surface expression, dynamics, seismicity, and deep structure. Continental transform faults are dominantly highly localized strike-slip shear zones hundreds of kilometers long that accumulate tens to hundreds of kilometers of displacement. In contrast to geometrically variable continental transforms, oceanic transform faults have more distinct architecture in which tens to hundreds of kilometers long active transform fault sections connecting two spreading centers are extended from both sides by even longer inactive fracture zones of similar orientation. Indeed, both continental and especially oceanic transforms are zones of significant rheological weakness and the absence of frictional healing, which are prerequisites for their existence, long-term stability, and relatively quiet seismicity.