Multiple strike‐slip fault sets: A case study from the Dead Sea Transform

Abstract

In many strike‐slip tectonic settings, large rotations of crustal blocks about vertical axes have been inferred from paleomagnetic data. These blocks are bounded by sets of parallel faults which presumably accommodate the relative motion between the blocks as regional deformation progresses. A mechanical model suggests that rotations greater than ϕc = 25° to 45° must be accommodated by more than one set of faults, with the angle ϕc between their directions, consequently the sum of the angles between sets must be roughly equal to the total tectonic material rotation. To test this model we investigated the fault geometry and field relationship of fault sets in the Mt. Hermon area in northern Israel, where paleomagnetic declination data imply 69°±13° counterclockwise (CCW) block rotation. The statistical and field relationship analysis of over 315 faults shows that the faulting is predominantly right lateral strike slip consisting of three distinct sets. The oldest set strikes 254°, the second oldest set strikes 295° and the youngest strikes 331°. This last direction is consistent also with the current north‐south direction of the maximum principal stress axis. The angle ϕc between the first and second sets is 41° and between the second and third sets 36°, in good agreement with the ϕc angle predicted from mechanical considerations. The sum of the two angles is 77°CCW, in good agreement with the 69°±13°CCW paleomagnetically derived rotation. The results suggest specifically that the sequential development of multiple intersecting fault sets is responsible for the faulting in the Mt. Hermon area and generally that the model of block rotation with multiple faults provides very good simple rules for analyzing very complex fault patterns.