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  • 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics  (4)
  • Southern Apennines  (2)
  • 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous  (1)
  • 1
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    Analysis of the 9 September 1998 Mw 5.6 Mercure earthquake sequence (Southern Apennines, Italy): A multidisciplinary approach (2012)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The Mercure earthquake (Mw 5.6) of September 9, 1998 and the associated aftershocks occurred in a small Pleistocene–Holocene continental basin of the Southern Apennines, in a region of low instrumental and moderate historical seismicity. Seismological, photogeological and field survey data were analyzed and integrated in order to identify the likely seismogenic structure, to depict its 3-D geometry and kinematics and to provide further constraints to the seismogenic potential of the rupture processes in the study area. The mainshock occurred at the NW edge of the seismic sequence (40.03°N and 15.95°) at a depth of 10.5± 1.5 km. The aftershocks volume was determined from the relocation of about 200 events (1.1=Ml=3.9) registered by local networks from September 10 to October 12, 1998. The relocation procedure was based on choosing P and S waves for all the events and the definition of ten 9-layers velocity models appropriate for the different stations. The kinematics of the seismogenic deformation was defined through the computation of 36 well-constrained focal mechanisms. The seismological and geological stress tensors were determined through inversion of focal mechanisms and fault slip data. Both of them resulted in the tensional type, with ENE–WSW and NE–SW trending σ3 axis, respectively. The map and the section distribution of the aftershocks sequence depicts an average NW–SE striking and 60° SW-dipping seismogenic volume. Most of the events (80%) were located at depths between 3 and 8 km in the footwall of the Mercure basin (MBB) boundary fault but along the possible down-dip continuation of a previously unidentified, N120°E striking and WSW-dipping, Holocene normal fault alignment, which extends from Castello Seluci to Piana Perretti and Timpa della Manca (CPST fault). A small percentage of events (10%) were located at depths between 10 and 12 km where the CPST seismogenic fault may detach. The reconstructed rupture area (RA) of the Mercure 1998 earthquake has an along-strike length (L) of about 9 km and a down-dip width (W) of about 9 km, yielding a total area of approximately 81 km2 . On the other hand, the L and W dimension of the entire individual seismogenic structure identified as responsible for the earthquake, e.g. the CPST fault, are about 19 and 12 km, respectively, with a consequent RA of about 230 km2 . This may imply a maximum magnitude (Mw) equal to 6.3 which lead us to compare the Mercure area, in terms of seismogenic hazard, to the adjacent Pollino-Castrovillari area where strong paleoseismological events are documented.
    Description: Published
    Description: 210–225
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Southern Apennines ; Stress-distribution ; Earthquake location ; Seismotectonics ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Seismotectonics of strike–slip earthquakes within the deep crust of southern Italy: Geometry, kinematics, stress field and crustal rheology of the Potenza 1990–1991 seismic sequences (Mmax 5.7) (2008)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We present a revision and a seismotectonic interpretation of deep crust strike–slip earthquake sequences that occurred in 1990– 1991 in the Southern Apennines (Potenza area). The revision is motivated by: i) the striking similarity to a seismic sequence that occurred in 2002 ∼140 km NNW, in an analogous tectonic context (Molise area), suggesting a common seismotectonic environment of regional importance; ii) the close proximity of such deep strike–slip seismicity with shallow extensional seismicity (Apennine area); and iii) the lack of knowledge about the mechanical properties of the crust that might justify the observed crustal seismicity. A comparison between the revised 1990–1991 earthquakes and the 2002 earthquakes, as well as the integration of seismological data with a rheological analysis offer new constraints on the regional seismotectonic context of crustal seismicity in the Southern Apennines. The seismological revision consists of a relocation of the aftershock sequences based on newly constrained velocity models. New focal mechanisms of the aftershocks are computed and the active state of stress is constrained via the use of a stress inversion technique. The relationships among the observed seismicity, the crustal structure of the Southern Apennines, and the rheological layering are analysed along a crustal section crossing southern Italy, by computing geotherms and two-mechanism (brittle frictional vs. ductile plastic strength) rheological profiles. The 1990–1991 seismicity is concentrated in a well-defined depth range (mostly between 15 and 23 km depths). This depth range corresponds to the upper pat of the middle crust underlying the Apulian sedimentary cover, in the footwall of the easternmost Apennine thrust system. The 3D distribution of the aftershocks, the fault kinematics, and the stress inversion indicate the activation of a right-lateral strike–slip fault striking N100°E under a stress field characterized by a sub-horizontal N142°-trending σ1 and a sub-horizontal N232°-trending σ3, very similar to the known stress field of the Gargano seismic zone in the Apulian foreland. The apparent anomalous depths of the earthquakes (N15 km) and the confinement within a relatively narrow depth range are explained by the crustal rheology, which consists of a strong brittle layer at mid crustal depths sandwiched between two plastic horizons. This articulated rheological stratification is typical of the central part of the Southern Apennine crust, where the Apulian crust is overthrusted by Apennine units. Both the Potenza 1990–1991 and the Molise 2002 seismic sequences can be interpreted to be due to crustal E–W fault zones within the Apulian crust inherited from previous tectonic phases and overthrusted by Apennine units during the Late Pliocene–Middle Pleistocene. The present strike–slip tectonic regime reactivated these fault zones and caused them to move with an uneven mechanical behaviour; brittle seismogenic faulting is confined to the strong brittle part of the middle crust. This strong brittle layer might also act as a stress guide able to laterally transmit the deviatoric stresses responsible for the strike–slip regime in the Apulian crust and may explain the close proximity (nearly overlapping) of the strike–slip and normal faulting regimes in the Southern Apennines. From a methodological point of view, it seems that rather simple two-mechanism rheological profiles, though affected by uncertainties, are still a useful tool for estimating the rheological properties and likely seismogenic behaviour of the crust.
    Description: Published
    Description: 281–300
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Strike–slip seismicity; ; Deep crust; ; Active stress; ; Crustal rheology; ; Seismotectonics; ; Southern Apennines ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Morphotectonic analysis of the Lunigiana and Garfagnana grabens (northern Apennines, Italy): Implications for active normal faulting (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: This work integrates existing structural geology data with new detailed geomorphic analyses of the fluvial network to characterize active and potentially seismogenic faults bordering the Lunigiana and Garfagnana basins in the northern Apennines of Italy. These two basins are NW–SE-oriented asymmetric grabens, bordered by several normal faults with a poorly known, but probable recent slip history. Several strong earthquakes (M 5.0–6.5) have occurred in the area in the last millennium, demonstrating that this is one of the most seismically active areas of the northern Apennines. However, the lack of reliable instrumental data for strong earthquakes, generally low deformation rates, and poor exposures of faulted Quaternary sediments render the characterization of active, seismogenic faults problematic. Here, we quantify the relationships between faults and watershed-scale geomorphology using 10-m digital topography to extract channel and basin metrics, such as steepness, concavity, and stream length-gradient indices of modeled river longitudinal profiles. In particular, convex segments of longitudinal profiles (knickpoints) are investigated in the spatial context of suspected active faults. Several knickpoints arise locally from juxtaposed rock types of different erodibility; however, many others mapped along major normal faults have a clear tectonic origin. In fact, the height of the footwall knickpoints (the closest to the fault trace) varies along-strike the fault, increasing toward the fault center and tapering off toward the fault tips, mimicking the expected displacement profile of a fault. In these cases, we consider the knickpoint height as a proxy of the fault throw accumulated by the youngest fault activity, probably during the late Quaternary. The along-strike distribution of knickpoint heights helps in defining the likely segmentation pattern of the fault system. The identified active normal fault segments have lengths ranging from 9.5 to 28.5 km. The inferred late Quaternary throw rate ranges from 0.3 to 0.8 mm/a; however, the absence of any offset datable material limits our ability to assign precise numeric ages and rates of offset to the faulting.
    Description: Published
    Description: 293-311
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Northern Apennines ; Active fault ; Normal fault ; Tectonic geomorphology ; Knickpoint ; Geomorphic indices ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    A multidisciplinary approach to the seismotectonics of the Lunigiana and Garfagnana extensional basins (Northern Tuscany, Italy) (2007)
    Società Geologica Italiana
    Details
    Publication Date: 2019-11-14
    Description: New geological and morpho-structural surveys are integrated with seismological and seismic reflection data in order to define the active and potentially seismogenic sources of the Lunigiana and Garfagnana extensional basins (Tuscany, Northern Italy). The seismogenic role of the E-W-striking transfer fault between the Lunigiana and Garfagnana basins, located at the northern termination of the Apuane metamorphic core, and its possible association with a number of historical earthquakes are also discussed.
    Description: Published
    Description: 88-89
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: open
    Keywords: Seismotectonics, seismic reflection data ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    Crustal structure and seismotectonics of central Sicily (southern Italy): new constraints from instrumental seismicity (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2024-05-09
    Description: In this paper, we propose a new model of the crustal structure and seismotectonics for central Sicily (southern Italy) through the analysis of the depth distribution and kinematics of the instrumental seismicity, occurring during the period from 1983 to 2010, and its comparison with individual geological structures that may be active in the area. The analysed data set consists of 392 earthquakes with local magnitudes ranging from 1.0 to 4.7. We defined a new, detailed 1-D velocity model to relocate the earthquakes that occurred in central Sicily, and we calculated a Moho depth of 37 km and a mean VP/VS ratio of 1.73. The relocated seismic events are clustered mainly in the area north of Caltanissetta (e.g. Mainland Sicily) and in the northeastern sector (Madonie Mountains) of the study area; only minor and greatly dispersed seismicity is located in the western sector, near Belice, and along the southern coast, between Gela and Sciacca. The relocated hypocentral distribution depicts a bimodal pattern: 50 per cent of the events occur within the upper crust at depths less than ~16 km, 40 per cent of the events occur within the middle and depth crust, at depths between 16 and 32 km, and the remaining 10 per cent occur at subcrustal depths. The energy release pattern shows a similar depth distribution. On the basis of the kinematic analysis of 38 newly computed focal plane solutions, two major geographically distinct seismotectonic domains are distinguished: the Madonie Mountain domain, with prevalent extensional and extensional-oblique kinematics associated with upper crust Late Pliocene–Quaternary faulting, and the Mainland Sicily domain, with prevalent compressional and compressional-oblique kinematics associated with thrust faulting, at mid to deep crust depth, along the north-dipping Sicilian Basal Thrust (SBT). The stress inversion of the Mainland Sicily focal solutions integrated with neighbouring mechanisms available in the literature highlights a regional homogeneous compressional tensor, with a subhorizontal NNW–SSE-striking σ1 axis. In addition, on the basis of geodetic data, the Mainland Sicily domain may be attributed to the SSE-ward thrusting of the Mainland Sicily block along the SBT plane. Seismogenic shearing along the SBT at mid-crustal depths was responsible for the unexpected Belice 1968 earthquake (Mw 6.1), with evident implications in terms of hazard assessment.
    Description: Published
    Description: 1237-2252
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: 3.2. Tettonica attiva
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: 5.2. TTC - Banche dati di sismologia strumentale
    Description: JCR Journal
    Description: restricted
    Keywords: Seismicity and tectonics ; Continental tectonics: compressional ; Dynamics: seismotectonics ; Crustal structure ; Europe ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    The April 2009 Aquila (central Italy) seismic sequence (Mw6.3): A preliminary seismotectonic picture, (2015)
    Nova Science Publishers, New York
    Details
    Publication Date: 2024-05-09
    Description: On April 6, 2009, an Mw 6.3 earthquake struck the town of L’Aquila in the Abruzzo region in central Italy. It was followed by a long seismic crisis with other four events with Mw between 5.1 and 5.6. Seismological and geological data point out an upper crust extensional stress field with an average WSW-ENE tensional axis. In the course of the seismic sequence, two distinct en échelon fault sources were activated: first, the SW-dipping Paganica normal fault, which is associated with the Mw 6.3 event; and, subsequently, the southern part of the WSW-dipping Gorzano normal fault.Co-seismic ground deformation (open fissures, en échelon cracks and shear planes with centimetric downthrows) was surveyed for ~ 13 km along the Paganica fault. The integration of the information from this last Italian earthquake with the previous seismotectonic background has allowed us to further detail the 3-D shape and the size of some of the individual seismogenic sources of the Apennine active extensional belt.
    Description: Published
    Description: 1-17
    Description: 2T. Tettonica attiva
    Description: restricted
    Keywords: L’Aquila, Apennines, central Italy ; seismogenic source ; normal fault ; fault segmentation ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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