The 1994 Sefidabeh earthquakes in eastern Iran: blind thrusting and bedding-plane slip on a growing anticline, and active tectonics of the Sistan suture zone

In 1994 a sequence of five earthquakes with M-w 5.5-6.2 occurred in the Sis tan belt of eastern Iran, all of them involving motion on blind thrusts wit h centroid depths of 5-10 km. Coseismic ruptures at the surface involved be dding-plane slip on a growing hanging-wall anticline displaying geomorpholo gical evidence of uplift and lateral propagation. The 1994 earthquakes were associated with a NW-trending thrust system that splays off the northern t ermination of a major N-S right-lateral strike-slip fault. Elevation change s along the anticline ridge suggest that displacement on the underlying thr ust dies out to the NW, away from its intersection with the strike-slip fau lt. This is a common fault configuration in eastern Iran and accommodates o blique NE-SW shortening across the N-S deforming zone, probably by anticloc kwise rotations about a vertical axis. This style of fault kinematics may b e transitional to a more evolved state that involves partitioning of the st rike-slip and convergent motion onto separate subparallel faults.