The contribution of regional uplift and coseismic slip to the vertical crustal motion in the Messina Straits, southern Italy: evidence from raised Late Holocene shorelines

Detailed mapping and dating of raised Late Holocene shorelines in southernCalabria, central Mediterranean region, reveals that the superposed shoreline record ofuplift has both steady and abrupt components. Analysis reveals quantitative constraintsmay be applied to displacement partitioning between regional and fault-relatedsources in a context dominated by forearc uplift and extension above a retreating slab.Rapid displacements of arguable coseismic origin occurred at 1.9 and 3.5 ka andpossibly at 5 ka and show a consistent site value, pattern of along-strike variation, andrecurrence time (1.6 ka). The source of the rather large (1.5–2.0 m) slip per eventbased on the raised shoreline is not directly known and tentatively coincides with theScilla extensional fault, which is inferred to run largely offshore. Although largeuncertainties exist on the trace location, length, and seismogenic potential of the fault,our findings suggest that a substantial fraction of Holocene displacement isaccommodated by coseismic footwall uplift. Precise compensation for sea level changesconstrains Late Holocene steady uplift during the interseismic intervals at 1 mm/yr, avalue consistent with long-term (0.1–1 Ma) estimates of regional uplift. Thus, LateHolocene total uplift of a 20-km stretch of coastline at 1.6–2.1 mm/yr is nearlyequally balanced between regional and coseismic components. Appraisal of the presentelevation attained by a suite of 125 ka and younger marine terraces indicate that rapid netuplift occurred in two episodes: (1) 100–80 ka and (2) after 5 ka; given theconstancy in regional uplift rate, the two episodes are attributable to enhanced fault sliprate. Efficient seismic strain release was clustered in intervals of 10–20 ka andintercalated with a 80-Ka-long period of fault quiescence.