Reappraisal and Analysis of Macroseismic Data for Seismotectonic Purposes: The Strong Earthquakes of Southern Calabria, Italy

Abstract

In tectonically active areas, such as the Italian peninsula, studying the faults responsible for strong earthquakes is often challenging, especially when the earthquakes occurred in historical times. In such cases, geoscientists need to integrate all the available information from historical reports, surface geology, and geophysics to constrain the faults responsible for the earthquakes from a seismotectonic point of view. In this paper, we update and review, according to the EMS-98 scale, the macroseismic fields of the five main events of the 1783 Calabria sequence (5, 6, and 7 February, 1 and 28 March, Mw 5.9 to 7.1), two other destructive events within the same epicentral area of the 1783 sequence (1791, Mw 6.1 and 1894, Mw 6.1), plus the Messina Strait 1908 earthquake (Mw 7.1). For the 1783 seismic sequence, we also elaborate an updated and new catalog of coseismic effects. The new macroseismic fields were analyzed using a series of MATLAB algorithms to identify (1) the unitarity of the field or its partitioning in sub-sources and (2) the field and sub-fields’ main elongation. A collection of earthquake scale laws from literature was used to compute the average source parameters (length, width, and area) with their range of variability, and an elliptical map-view representation of the source geometry was calculated and made available. The analyses of such data allow us to speculate on the earthquakes/faults association, as well as propose new interpretations and reconstruct the space–time evolution of the significant southern Calabria seismic sequences in the last five centuries.

Multidisciplinary analysis of 3D seismotectonic modelling: a case study of Serre and Cittanova faults in the southern Calabrian Arc (Italy)

“…Adopting a multidisciplinary approach based on morphostructural field data integrated with seismological and geodetic data, we modelled the 3D geometry of the Cittanova and Serre faults in southern Calabria, performed the FRM simulation for these faults, and evaluated their propensity to slip in the MOVE environment. On the basis of our results (maximum expected magnitude, vertical slip evaluation, and slip tendency) and according to the historical report (de Dolomieu ( 1784)) and previous works (Jacques et al, 2001;Andrenacci et al, 2023), we found that CF and SRF (called "debated seismogenic sources" in DISS; DISS Working Group, 2021, https://diss.ingv.it/) are the best candidate sources of the 5 February, 7 February, and 1 March 1783 events. On the contrary, the Gioia Tauro and Mesima faults do not exhibit surface evidence (e.g., coseismic scarplet, cumulative morphological scarps, kinematic indicators, and tectonic control on the drainage network) that would testify a recent activity associated with them.…”

“…Frontiers in Earth Science frontiersin.org Jacques et al, 2001), macroseismic data (from Andrenacci et al, 2023), and simulated coseismic displacement (Figure 10A) confirms the choice of the CF and SRF faults, respectively, as the most likely causative sources for the considered events. Figure 10C shows that it is possible to visualize the profiles of vertical coseismic displacement across CF and SRF.…”

“…Concerning the seismic source models of 5 February, 7 February, and 1 March, some authors proposed the CF and SRF west-dipping normal faults as responsible sources (Tapponnier et al, 1987;Ghisetti, 1992;Tortorici et al, 1995;Monaco and Tortorici, 2000;Jacques et al, 2001) (Figure 1A, DSS; Debated Seismic Source). This hypothesis was supported by field geologic and morphotectonic data and observation by the distribution of the high-damage sites as exploited by the mesoseismal areas of the 1783 sequence (Baratta, 1901) and revisited macroseismic data (Andrenacci et al, 2023), the observed coseismic fracturing (de Dolomieu, 1784), and also by paleoseismological studies (Galli and Bosi, 2002;Galli and Peronace, 2015). Conversely, other authors inferred ruptures along the Gioia Tauro and the Mesima east-dipping blind low angle (~30 °) normal faults for the same events (Valensise and D'Aaddezio, 1994;Cucci et al, 1996;Peruzza et al, 1996;Loreto et al, 2013) (see also Figure 1A, ISS: Individual Seismic Source).…”

“…In this work, a multidisciplinary approach has been followed to reconstruct, in the MOVE Software Suite environment (granted by Petroleum Experts Limited; www.petex.com), the 3D geometry of the Cittanova fault (CF) and Serre fault (SRF), the longest tectonic structures occurring in southern Calabria (Tapponnier et al, 1987;Ghisetti, 1992;Tortorici et al, 1995;Monaco and Tortorici, 2000;Jacques et al, 2001;Galli and Bosi, 2002). These faults, belonging to the A2 category, are defined by Jacques et al (2001) and recently, starting from macroseismic data, by Andrenacci et al (2023) as the seismogenic sources of the 5 and 7 February 1783 seismic events, whereas other authors (e.g., Valensise and D'Aaddezio, 1994;Cucci et al, 1996) consider the Gioia Tauro and Mesima faults, belonging to the A1 category, as the most likely sources for the same seismic events. The open debate between different geometric interpretations (E-dipping vs. W-dipping) reported in DISS and different schools of thought on the sources of the 1783 seismic sequence proves that the development of a 3D model for these faults may be crucial to better characterize the seismotectonics of the area and evaluate its seismic potential.…”

Generation of the Quaternary Normal Faults in the Messina Strait (Italy)

“…Since the Messina Strait could become the site of a long bridge between Sicily and Calabria, recognizing the location and geometry of the main seismic sources in that area may be particularly useful. Several attempts to get this information have been made by studying the effects of the last two main earthquakes which affected the area, one in the northern Messina trough (M = 6.2) on 6 February 1783 (e.g., [1]) and one in the Messina sphenocasm (M = 7.1) on 28 December 1908 [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Some of the fault models indicated by the above authors for the most studied event, the 1908 shock, are shown in Figure 1.…”