Structure and morphology of an active conjugate relay zone, Messina Strait, southern Italy

Messina Strait is a narrow fault-bounded marine basin that separates the Calabrian peninsula from Sicily in southern Italy. It sits in a seismically active region where normal fault scarps and raised Quaternary marine terraces record ongoing extension driven by southeastward rollback of the Calabrian subduction zone. A review of published studies and new data shows that normal faults in the Messina Strait region define a conjugate relay zone where displacement is transferred along strike from NW-dipping normal faults in the northeast (southern Calabria) to the SE-dipping Messina-Taormina normal fault in the southwest (offshore eastern Sicily). The narrow marine strait is a graben undergoing active subsidence within the relay zone, where pronounced curvature of normal faults results from large strain gradients and clockwise rotations related to fault interactions. Based on regional fault geometries and published age constraints, we infer that normal faults in southern Calabria migrated northwest while normal faults in NE Sicily migrated southeast during the past ca. 2–2.5 Myr. This pattern has resulted in tectonic narrowing of the strait through time by inward migration of facing normal faults and rapid mantle-driven uplift.