Seismotectonic outline of South-Eastern Sicily: An evaluation of available options for the earthquake fault rupture scenario

Seismotectonic information and interpretations available for SE Sicily suggest three groups of possible sources for the M = 7.1 - 7.5 mainshock of 1693 and its strong foreshock: (1) normal faults belonging to the Ibleo Maltese Escarpment (also: Malta Escarpment); (2) normal faults associated with the two adjacent Simeto and Scordia-Lentini structures; (3) a transfer structure between the Sicily Straits rift system and the two grabens to the north. We use a new kinematic model to invert the data sets of macroseismic intensities of the two earthquakes to retrieve information on their sources. For this, we invert point observations, or intensities tessellated with the Voronoi polygons technique, and treat residuals of inversion in the matrix of points, or in the tessellated plane. Our inversions of the regional intensity patterns using this technique show that family N° 3 is a good candidate for the foreshock of 9 January 1693. For the mainshock of 11 January 1693, an almost perfect synthesis of its intensity IX area was obtained with our model and a source belonging to family N° 3. However, all information considered (tsunami included), this earthquake could have been produced either by (3) or by a fault located along the Ibleo-Maltese Escarpment, and tangential to the Augusta and Siracusa promontories.