Abstract
Abstract. We reconstruct the 3D fault model of the structures causative of the 2010–2014 Pollino seismic activity by integrating structural–geological and high-resolution seismological data. We constrained the model at the surface with fault-slip data, and at depth, by using the distributions of selected high-quality relocated hypocenters. Relocations were performed through the non-linear Bayloc algorithm, followed by the double-difference relative location method HypoDD applied to a 3D P-wave velocity model. Geological and seismological data highlight an asymmetric active extensional fault system characterized by an E- to NNE-dipping low-angle detachment, with high-angle synthetic splays, and SW- to WSW-dipping, high-angle antithetic faults. Hypocenter clustering and the time–space evolution of the seismicity suggest that two sub-parallel WSW-dipping seismogenic sources, the Rotonda–Campotenese and Morano–Piano di Ruggio faults, are responsible for the 2010–2014 seismicity. The area of the seismogenic patches obtained projecting the hypocenters of the early aftershocks on the 3D fault planes, are consistent with the observed magnitude of the strongest events (Mw=5.2, and Mw=4.3). Since earthquake-scaling relationships provide maximum expected magnitudes of Mw=6.4 for the Rotonda–Campotenese and Mw=6.2 for the Morano–Piano di Ruggio faults, we may suppose that, during the sequence, the two structures did not entirely release their seismic potential. The reconstructed 3D fault model also points out the relationships between the activated fault system and the western segment of the Pollino Fault. The latter was not involved in the recent seismic activity but could have acted as a barrier to the southern propagation of the seismogenic faults, limiting their dimensions and the magnitude of the generated earthquakes.
Highlights
In recent years, the reconstruction of 3D fault models, obtained by integrating surface ad subsurface data, has become an increasingly practiced methodology for seismotectonic studies (e.g., Lavecchia et al, 2017; Castaldo et al, 2018; Klin et al, 2019; Ross et al, 2020; Porreca et al, 2020; Barchi et al, 2021; Di Bucci et al, 2021; SCEC, 2021)
Relocations were performed through the non-linear Bayloc algorithm, followed by the double-difference relative location method HypoDD applied to a 3D P-wave velocity model
Most the kinematic axes related to the inverted data belong to a normal-fault regime, as pointed out by the triangle in Fig. 5 (Frohlich, 2001)
Summary
The reconstruction of 3D fault models (hereinafter referred to as 3DFM), obtained by integrating surface ad subsurface data, has become an increasingly practiced methodology for seismotectonic studies (e.g., Lavecchia et al, 2017; Castaldo et al, 2018; Klin et al, 2019; Ross et al, 2020; Porreca et al, 2020; Barchi et al, 2021; Di Bucci et al, 2021; SCEC, 2021). Detailed structural–geological data are used to define the active faults geometry at the surface, whereas high-quality geophysical data are needed to constrain the shape of the sources at depth. The 3DFM building helps determine the spatial relationships and the interactions between adjacent sources and identify any barriers hampering the propagation of the coseismic rupture at depth. Such an approach leads to accurately estimating the area. D. Cirillo et al.: Structural complexities and tectonic barriers controlling recent seismic activity of the seismogenic fault, and the expected magnitude
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