Abstract
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.
Highlights
The 28th December 1908 Messina earthquake (Mw 7.1) is the most destructive 20th and 21st century earthquake in Europe, with a death toll of >80,0001,2, yet the geometry and kinematics of the fault that ruptured are still a source of debate
Some studies suggest the existence of an offshore structure, the so-called “Taormina Fault”, that offsets the pre-Pleistocene basement, and propagated upwards to produce a fault-related syncline along its trace from Messina town to Taormina town[10,28,29,30,31] (Fig. 1), actively deforming sequences of Late Quaternary marine terraces and Holocene coastal notches[28,30,31]
The profile of the co-seismic vertical deformation motions compared to other well-mapped normal faulting surface ruptures in Figs 3a and 4a suggests, even before modelling, that an east-dipping fault is likely to be responsible for the earthquake
Summary
The 28th December 1908 Messina earthquake (Mw 7.1) is the most destructive 20th and 21st century earthquake in Europe, with a death toll of >80,0001,2, yet the geometry and kinematics of the fault that ruptured are still a source of debate. Well-mapped high-angle capable faults around the Messina Strait, located both onshore and offshore, are known to coincide with offsets of basement stratigraphy and control the location of sedimentary basins[9,20] (Figs 1 and 2) These offsets will have developed due to repeated faulting which offsets the surface through time, so the fact that they have not been modelled in detail is a clear omission in the study of this major earthquake. Plotting of the levelling data as a function of distance E-W reveals the potential importance of east-dipping capable faults (Fig. 3a) This plot reveals, even before modelling, that the pattern of uplift and subsidence strongly resembles that of other large normal faulting earthquakes whose relatively steep source fault dips and dip directions are well known from mapped surface ruptures and epicentre-to-rupture distances[21,22]. The severe tsunami effects have been related to co-seismic displacement of the sea floor in the Messina offshore[3]; this evidence might explain why the extensive surface fault ruptures expected on land for such a large magnitude event have not been described in the literature
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