Fault bends, and associated changes in fault dip, play a key role in explaining the scatter in maximum offset versus surface rupture length fault scaling relationships. Detailed field measurements of the fault geometry and magnitude of slip in the 2016–2017 Central Italy earthquake sequence, alongside three examples from large historical normal‐faulting earthquakes in different tectonic settings, provide multiple examples in which coseismic throw increases across bends in fault strike where dip also increases beyond what is necessary to accommodate a uniform slip vector. Coseismic surface ruptures produced by two mainshocks of the 2016–2017 Central Italy earthquake sequence (24 August 2016 Mw 6.0 and 30 October 2016 Mw 6.5) cross a ~0.83‐km amplitude along‐strike bend, and the coseismic throws for both earthquakes increase by a factor of 2–3, where the strike of the fault changes by ~28o and the dip increases by 20–25o. We present similar examples from historical normal faulting earthquakes (1887, Sonora earthquake, Mw 7.5; 1981, Corinth earthquakes, Mw 6.7–6.4; and 1983, Borah Peak earthquake, Mw 7.3). We demonstrate that it is possible to estimate the expected change in throw across a bend by applying equations that relate strike, dip, and slip vector to horizontal strain conservation along a nonplanar fault for a single earthquake rupture. The calculated slip enhancement in bends can explain much of the scatter in maximum displacement (Dmax) versus surface rupture length scaling relationships. If fault bends are unrecognized, they can introduce variation in Dmax that may lead to erroneous inferences of stress drop variability for earthquakes, and exaggerate maximum earthquake magnitudes derived from vertical offsets in paleoseismic data sets.

In order to investigate the deformation within the upper plate of the Calabrian subduction zone, we have mapped and modeled a sequence of Late Quaternary paleoshorelines tectonically deformed by the Capo D'Orlando normal fault, NE Sicily, which forms part of the actively deforming Calabrian Arc. In addition to the 1908 Messina Strait earthquake (M w 7.1), this region has experienced damaging earthquakes, possibly on the Capo D'Orlando Fault; however, it is not considered by some to be a potential seismogenic source. Uplifted Quaternary paleoshorelines are preserved on the hangingwall of the Capo D'Orlando Fault, indicating that hangingwall subsidence is counteracted by regional uplift, likely because of deformation associated with subduction/collision. We attempt to constrain the relationship between regional uplift, crustal extensional processes, and historical seismicity, and we quantify both the normal and regional deformation signals. We report uplift variations along the strike of the fault and use a synchronous correlation technique to assign ages to paleoshorelines, facilitating calculation of uplift rates and the fault throw rate. Uplift rates in the hangingwall increase from 0.4 mm/year in the center of the fault to 0.89 mm/year beyond its SW fault tip, suggesting 0.5 mm/year of fault-related subsidence, which implies a throw rate of 0.63 ± 0.02 mm/year, and significant seismic hazard. Overall, we emphasize that upper plate extension and related vertical motions complicate the process of deriving information on the subduction/collision process, such as coupling and slip distribution on the subduction interface, parameters that are commonly inferred for other subduction zones without considering upper plate deformation.

Preserved sets of marine terraces and palaeoshorelines above subduction zones provide an opportunity to explore the long‐term deformation that occurs as a result of upper‐plate extension. We investigate uplifted palaeoshorelines along the South Central Crete Fault and over its western tip, located above the Hellenic Subduction Zone, in order to derive uplift rates and examine the role that known extensional faults contribute to observed coastal uplift. We have mapped palaeoshorelines and successfully dated four Late‐Quaternary wave‐cut platforms using in situ 36Cl exposure dating. These absolute ages are used to guide a correlation of palaeoshorelines with Quaternary sea level highstands from 76.5 to ~900 ka; the results of which suggest that uplift rates vary along fault strikes but have been constant for up to 600 ka in places. Correlation of palaeoshorelines across the South Central Crete Fault results in a throw‐rate of 0.41 mm/year and, assuming repetition of 1.1‐m slip events, a fault‐specific earthquake recurrence interval of approximately 2,700 years. Elastic‐half‐space modeling implies that coastal uplift is related to offshore upper‐plate extensional faults. These faults may be responsible for perturbing the uplift rate signals in the south central Crete area. Our findings suggest that where uplifted marine terraces are used to make inferences about the mechanisms responsible for uplift throughout the Hellenic Subduction Zone, and other subduction zones worldwide, the impact of upper‐plate extensional faults over multiple seismic cycles should also be considered.

Preserved sets of marine terraces and palaeoshorelines above subduction zones provide an opportunity to explore the long-term deformation that occurs as a result of upper-plate extension. We investigate uplifted palaeoshorelines along the South Central Crete Fault and over its western tip, located above the Hellenic Subduction Zone, in order toderive uplift rates and examine the role that known extensional faults contribute to observed coastal uplift. We have mapped palaeoshorelines and successfully dated four Late-Quaternary wave-cut platforms using in-situ 36Cl exposure dating. These absolute ages are used to guidea correlation of palaeoshorelines with Quaternary sea-level highstands from 76.5 to ~900 ka; the results of which suggest that uplift rates vary along fault strikes but have been constant for up to 600 ka in places. Correlation of palaeoshorelines across the SCCF results in a throw-rate of 0.41 mm/yr and, assuming repetition of 1.1 m slip events, a fault-specific earthquake recurrence interval of approximately 2700 years. Elastic-half space modellingimplies that coastal uplift is related to offshore upper-plate extensional faults. These faults may be responsible for perturbing the uplift rate signals in the south central Crete area. Our findings suggest that where uplifted marine terraces are used to make inferences about the mechanisms responsible for uplift throughout the Hellenic Subduction Zone, and other subduction zones worldwide, the impact of upper-plate extensional faults over multipleseismic cycles should also be considered.

The 28th December 1908 Messina earthquake (Mw 7.1), Italy, caused >80,000 deaths and transformed earthquake science by triggering the study of earthquake environmental effects worldwide, yet its source is still a matter of debate. To constrain the geometry and kinematics of the earthquake we use elastic half-space modelling on non-planar faults, constrained by the geology and geomorphology of the Messina Strait, to replicate levelling data from 1907–1909. The novelty of our approach is that we (a) recognise the similarity between the pattern of vertical motions and that of other normal faulting earthquakes, and (b) for the first time model the levelling data using the location and geometry of a well-known offshore capable fault. Our results indicate slip on the capable fault with a dip to the east of 70° and 5 m dip-slip at depth, with slip propagating to the surface on the sea bed. Our work emphasises that geological and geomorphological observations supporting maps of capable non-planar faults should not be ignored when attempting to identify the sources of major earthquakes.