![]() Convergent margins with oblique plate trajectories will also generate strike-slip faults in accretionary prisms, forearcs and backarcs. The characteristic zig zag dismembering of mid-ocean spreading ridges is caused by ridge transforms that accommodate the strain from oblique spreading. They form in oceanic and continental crust/lithosphere. Strike-slip faults occur in most plate tectonic settings, primarily at plate boundaries (like most other fault types). The present trajectory along Alpine Fault is also transpressional. Pacific plate trajectories at Hikurangi margin become increasingly oblique from north to south. The right-lateral Alpine Fault transform and its strike-slip fault splays (Marlborough fault system), in the context of other plate tectonic elements: the Hikurangi subduction zone that is linked to Alpine Fault via Hope Fault and the subduction zone at the south end of South Island where oceanic crust of the Australian Plate is subducting beneath the Pacific plate (opposite polarity to Hikurangi). But he was right… Jumping ahead a few years (and encapsulating several decades of science history in a single sentence), we now know this fault as the Alpine Fault, a dextral, or right-lateral transform strike-slip fault that also doubles as the boundary between the Pacific and Australian plates. ![]() Wellman’s hypothesis turned a few heads and invited its share of derision. The consensus at the time was that crustal movements were dominated by vertical displacements. The dislocation was the result of 600 km lateral shift along a major fault. In 1940 Harold Wellman and Dick Willett proposed that two groups of rocks at either end of the South Island of New Zealand, each having the same stratigraphic and lithologic characteristics, were at one time a single unit. The fault splays are clearly delineated by valleys. The intersection of splay faults that trend northeast indicated by black dots. The master fault is a prominent linear feature immediately left of the snow line (black arrow, bottom). An oblique view of Alpine Fault from the International Space Station.
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