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 southern Calabria, central Mediterranean region, reveals that the superposed shoreline record of uplift has both steady and abrupt components. Analysis reveals quantitative constraints may be applied to displacement partitioning between regional and fault-related sources 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 and possibly at ~5 ka and show a consistent site value, pattern of along-strike variation, and recurrence time (~1.6 ka). The source of the rather large (~1.5–2.0 m) slip per event based on the raised shoreline is not directly known and tentatively coincides with the Scilla extensional fault, which is inferred to run largely offshore. Although large uncertainties exist on the trace location, length, and seismogenic potential of the fault, our findings suggest that a substantial fraction of Holocene displacement is accommodated by coseismic footwall uplift. Precise compensation for sea level changes constrains Late Holocene steady uplift during the interseismic intervals at ~1 mm/yr, a value consistent with long-term (0.1–1 Ma) estimates of regional uplift. Thus, Late Holocene total uplift of a ~20-km stretch of coastline at ~1.6–2.1 mm/yr is nearly equally balanced between regional and coseismic components. Appraisal of the present elevation attained by a suite of 125 ka and younger marine terraces indicate that rapid net uplift occurred in two episodes: (1) ~100–80 ka and (2) after ~5 ka; given the constancy in regional uplift rate, the two episodes are attributable to enhanced fault slip rate. Efficient seismic strain release was clustered in intervals of 10–20 ka and intercalated with a ~80-Ka-long period of fault quiescence.