STRIKESLIP AND OBLIQUESLIP TECTONICS（STRIKESLIP和OBLIQUESLIP构造）.pdfVIP

173 STRIKE-SLIP AND OBLIQUE-SLIP TECTONICS Strike–slip faulting is a common mode of deformation in both continental and oceanic crust and occurs at a wide range of scales. Strike slip systems are relatively narrow and subvertical wrench zones along which two adjacent blocks move sideways, horizontally, parallel to the strike of the fault zone. For example, they are produced at transform plate boundaries where plates horizontally slide past one another. There is no net addition or subtraction of area to the crust. It is classically accepted that strike slip faulting occurs in a triaxial stress field in which the maximum and minimum principal stresses σ1 and σ3 lay in the horizontal plane and the intermediate principal stress σ2 is vertical. In a trigonometric system, a strike slip fault at an angle 0 θ 90° to σ1 is sinistral; it is dextral if 90 θ 180° . Nearly 45% of plate boundaries have a relative velocity vector markedly oblique ( 22°) to the boundary normal. 14% of plate boundaries have vectors nearly parallel to boundaries (within 22°). This implies that strike-slip tectonics is important, whether alone or as a component. Present-day plate tectonics document four main types of strike-slip systems: Tectonics – Strike-slip faults jpb -2017 174 Conservative plate boundaries Transform fault at oceanic plate boundaries Mid-Atlantic ridge Transform fault at continental plate boundaries Basin and Range Passive margins Bay of Biscay Destructive plate boundaries with oblique convergence Transpression at continental plate boundari