Simulation of Seismicity in the Block-structure Model of Italy and its Surroundings

Abstract

The numerical block-model of the lithosphere dynamics is used to simulate seismicity in Italy and its surroundings, based on the available structural and geodynamics information. The purpose of the study is to understand which are the tectonic processes that control the main features of the observed seismicity and the kinematics of the region. The influence of the rheology of the fault systems is studied as well. The model we use differs from other modeling approaches in that it simulates earthquakes and hence it possibly relates to seismicity and geodynamics. The model provides an effective capability to include the set of documented constraints supplied by widely available earthquake catalogs. This is done by means of the comparison of the GR relation, of the focal mechanisms and of the space distribution for observed and computed seismicity. The region is modeled as a system of perfectly rigid blocks, separated by infinitely thin fault planes, in viscoelastic interaction between themselves and with the underlying medium. The movement of the boundary blocks and of the underlying medium determines the motion of the blocks. The synthetic seismicity obtained with the defined block-model is similar to the observed one for the most seismically active areas. A linear frequency-magnitude (FM) relation (Gutenberg-Richter law) is obtained for synthetic earthquakes; the slope (b-value) of the FM plot appears larger for the synthetic seismicity than for the observed one. Nevertheless, the b-value is essentially larger in northern and central Italy than that in southern Italy, both in the model and in the observations. The analysis of the source mechanisms of the synthetic earthquakes shows a good agreement with the observations. In the model normal faulting is typical for the Apennines, the eastern edge of Sicily and the Calabrian arc, while reverse faulting takes place at the northwestern boundary of the Adriatic Sea, in the southern Alps and along the eastern edge of the Adria, along the Dinarides. The model correctly reproduces the extension zone along the Apennines and the contraction zone along the northwestern boundary of the Adriatic Sea; the counter-clockwise rotation of the Adria is mimed. The resulting movements of the blocks are in overall agreement with GPS (Global Positioning System) observations. The results of the modeling experiments suggest that the main features of dynamics and seismicity in the central Mediterranean region cannot be satisfactorily explained as a consequence of Africa and Eurasia convergence only; the passive subduction in the Calabrian arc and the different rheology of faults are essential as well

Carbonate metasomatism and CO2 lithosphere–asthenosphere degassing beneath the Western Mediterranean: An integrated model arising from petrological and geophysical data

“…The Oligocene to present evolution of the Western-Central Mediterranean region has been characterized by the separation of the Corsica-Sardinia block from the southern European margin, the opening of the Ligurian-Provençal, Algerian, and Valencia basins, and by the opening of the Tyrrhenian Sea and counter-clockwise rotation of the Italian peninsula (e.g., Doglioni et al 1997Doglioni et al , 1999Carminati et al 1998;Faccenna et al, 2001;Peresan et al, 2007). There is a general consensus that these structural modifications are related to Oligocene to present west-dipping 4 subduction of the African plate beneath the southern European margin, which migrated from west to east, up to its present position in the southern Tyrrhenian Sea.…”

“…The opening of the Tyrrhenian Sea and the counterclockwise rotation of the Italian peninsula resulted in the longitudinal stretching and fragmentation of the Apennine chain, with formation of several arc sectors separated by important transverse tectonic lines (e.g., the so-called 41° N parallel line, the Sangineto fault, the Tindari-Letojanni fault; Locardi, 1988;Turco and Zuppetta 1998;Rosenbaum et al, 2008). These structures separate crustal blocks characterized by different drifting velocity, structure of the lithosphere, and degrees of block rotation (Peresan et al, 2007), and by different compositions of the volcanism (Turco and Zuppetta 1998;Peccerillo, 1999;Peccerillo and Panza, 1999). Extensional tectonics affected the margin of the African foreland (Corti et al, 2006) where Oceanic Island Basalt (OIB)-type magmatism occurred, starting from the Miocene.…”

Modelling the seismic potential of the Indo-Burman megathrust

“…Therefore, due to the non-linear behavior of the model, non-local effects, cross-influence of the different input parameters the influence of a particular parameter on the result may be different (or even opposite) depending on the block structure geometry and type of movement. All these factors can be determined only by numerical experiments 22 – 24 .…”

Numerical Modelling of Lithospheric Block-and-Fault Dynamics: What Did We Learn About Large Earthquake Occurrences and Their Frequency?

“…Meanwhile, only models of type-III dealing with fault dynamics allow for simulating realistic earthquakes (Ismail-Zadeh et al, 2018). For example, several models were developed in the case of a large heterogeneous fault (e.g., Ben-Zion and Rice 1993;Lyakhovsky et al 2001;Zöller et al 2005;Lapusta and Liu 2009;Nodal and Lapusta 2010) and in the case of a system of faults (e.g., Gabrielov et al 1990Gabrielov et al , 2007Ward 1992Ward , 1996Ward , 2000Benites 1996, 2001;Panza et al 1997;Fitzenz and Miller 2001;Soloviev and Ismail-Zadeh 2003;Rundle et al 2006;Zhou et al 2006;, 2012aPeresan et al 2007;Zöller and Hainzl 2007;Pollitz 2009;Bielak et al 2010;Vorobieva et al 2014Vorobieva et al , 2019Vorobieva et al , 2021. The results of the modelling improved significantly our understanding of earthquake occurrences and seismic hazards.…”

“…The BAFD model was applied to study seismicity and statistics of earthquakes in several earthquake-prone areas, such as the south-eastern Carpathians (Panza et al 1997;Soloviev et al 1999;Ismail-Zadeh et al 1999), the central Alpine-Himalayan belt (Sobolev et al 1999), the western Alps (Vorobieva et al 2000;Soloviev and Ismail-Zadeh 2003), Sunda island arc (Soloviev and Ismail-Zadeh 2003), Tibet-Himalaya (Ismail-Zadeh et al 2007;Vorobieva et al 2017Vorobieva et al , 2021, Italy and its surroundings (Peresan et al 2007), Kachchh rift zone (Vorobieva et al 2014), and Caucasus (Soloviev and Gorshkov 2017;Vorobieva et al 2019). Here, we overview the application of the BAFD model to the orogenic regions, such as Carpathians, Caucasus, and Tibet-Himalaya, as well as to the Sunda arc, associated with the Indo-Australian plate subduction, which have been subjects to earlier surveys (Soloviev and Ismail-Zadeh 2003;Ismail-Zadeh et al 2012a, b;Ismail-Zadeh et al 2018).…”