Dipping faults rarely slip in a strike-slip sense. Commonly, dipping faults accommodate convergence or extension whereas strike-slip displacements occur on nearly vertical faults. Where stresses are oblique to a system of dipping and vertical faults, slip is observed to be partitioned between them according to the relationships of Anderson–Byerlee fault mechanics (Anderson, 1972, Byerlee, 1978, Sibson, 1985 and Jones and Wesnousky, 1992).
The September 24, 2013Mw7.7 Balochistan strike-slip earthquake is thus unusual in that it ruptured a 200+ km200+ km section of a curved reverse fault within the mechanically weak Makran accretionary prism of southern Pakistan (Fig. 1a). Despite fault dips of 45–75°, the earthquake slipped in a dominantly left-lateral sense (∼6:1 SS:DS ratio). The plate boundary zone near the triple junction between the Eurasia, India, and Arabia (Ormara microplate) plates (Fig. 1a), location of the Balochistan earthquake, is characterized by east–west oriented reverse faults. These include the Panjgur, Hoshab, and Nai Rub fault system (PHNFS) where the traces swing counter-clockwise as they approach the India plate (Lawrence et al., 1981). This rotation results in a striking curved structural grain to the fold belt in southeast Balochistan.