Abstract
Continental plate boundary zones are, generally, wide diffuse zones of deformation within which, in the upper 5 to 15 km, may be recognized blocks, which are bounded by fault zones within which strain is highly concentrated and along which slip rates are fairly high (2–30 m Ma−1). These blocks may be irregular flakes, defined by older crustal inhomogeneities of an upper brittle crust below which strain occurs in a ductile and more homogeneous lower crust. With examples from the convergent plate boundary zone of eastern Turkey and the southern Caribbean plate boundary zone of northern South America, we use plate slip rates and trends and slip rates of faults to construct block vector diagrams to deduce the sums of relative motion among block mosaics, slip rates and trends of ill defined block boundaries, and the extent to which blocks are internally strained.