![]() ![]() Twiss & Moores Fig 7.10 shows connection with normal faults and with thrusts.Ĭharacteristics of strike-slip zones Pure strike-slipĪ straight purely strike-slip fault can move without causing any distributed deformation in the wall rocks, so much of the interest in strike-slip zones relates to features where there is a departure from pure strike slip: transpression and transtension at a large scale, releasing and restraining bends at small scale (really just small scale transpressional and transtensional structures respectively). Slip can die out into distributed deformation, or fault can connect with another type of structure. Ramsay & Huber fig 23.37 shows restraining & releasing bends Releasing bends involve localized transtension. ![]() Where there is a component of extension across a belt of significant strike-slip, the environment is described as transtensional. Restraining bends are localized transpressional zones. Where there is a component of shortening across a belt of significant strike slip, the environment is described as transpressional. On a right lateral fault, right bands are releasing, left bands are restraining On a left lateral fault, left bends are releasing, right bends are restraining These can be characterized as left or right bends (Twiss & Moores fig 7.5) Note that though many strike slip faults are approximately straight (or rather, arcs of small circles) most have irregularities. Note that Twiss and Moores show this effect only in the case of folds in their fig 7.4). (In this case, a dextral fault all will rotate clockwise. Note that if ductile shearing occurs adjacent to the fault, any or all of these features can be rotated. If surface of earth is allowed to rise or fall in response to stress in wall of strike-slip fault, then associated dip slip faults and or folds may form. If deformation extends into surrounding rocks it may produce a number of associated structures. dextral separation but sinistral slip etc.) Under circumstances where there is a small amount of dip slip, but the beds intersected are even more gently dipping, the possibility arises that the separation may have the reverse sense of the slip (ie. Under these circumstances, strike separation of a surface is always in the same sense (sinistral or dextral) as the slip but dip separation may vary depending on the dip of the surface.ĭip separation depends mainly on the orientation of the intersected surface and has little to do with the true slip. This situation leads to conjugate strike slip faults intersecting in a vertical line.ĭefinition of strike slip tells us that horizontal component of slip predominates. Close to the earth's surface, Anderson's theory of stress and faulting tells us that strike slip faults predominated when 2 is vertical. Many but not all strike slip faults are steep. Major strike slip shear zones are found in metamorphic rocks of deeply eroded orogens.Ĭharacteristics of individual strike-slip faults We infer that at depth these zones are underlain by ductile shear zones at mid-crustal level. Many major transcurrent faults are actually fault zones - multiple strands of faults separate blocks that (at least for periods of time) are relatively rigid. Other major strike slip faults within continental crust are called transcurrent faults, but the distincition is not sharp - some zones of continental deformation are divided into microplates by some authors and not by others. Strike-slip faults that are plate boundaries are called transform faults. Faults where a large component of the slip vector is horizontal, parallel to the strike of the fault.
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