3D tomographic imaging of the southern Apennines (Italy): A statistical approach to estimate the model uncertainty and resolution

Matteis, Raffaella De; Romeo, Annalisa; Pasquale, Giuseppe; Iannaccone, Giovanni; Zollo, Aldo

doi:10.1007/s11200-010-0022-x

Cited by 10 publications

(4 citation statements)

References 51 publications

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“…We chose the P-wave velocity model by Barberi et al (2004) as the starting reference 1D velocity model for the preliminary hypocenter location and data pre-processing. Then, we applied a statistical procedure that allows to find the most reliable local reference 1D velocity model to be used as an input in the 3D tomography of the study area (Vanorio et al, 2005;De Matteis et al, 2010). Following this procedure, we generated 120 1D P-wave models characterized by velocity values randomly chosen in the range ±500 m/s around the value of the reference model for each layer (Figure 3A).…”

Section: Tomographic Methods and Inversion Strategymentioning

confidence: 99%

Crustal Structure of the Seismogenic Volume of the 2010–2014 Pollino (Italy) Seismic Sequence From 3D P- and S-Wave Tomographic Images

et al. 2021

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A tomographic analysis of Mt. Pollino area (Italy) has been performed using earthquakes recorded in the area during an intense seismic sequence that occurred between 2010 and 2014. 870 local earthquakes with magnitude ranging from 1.8 to 5.0 were selected considering the number of recording stations, the signal quality, and the hypocenter distribution. P- and S-wave arrival times were manually picked and used to compute 3D velocity models through tomographic seismic inversion. The resulting 3D distributions of VP and VS are characterized by high resolution in the central part of the investigated area and from surface to about 10 km below sea level. The aim of the work is to obtain high-quality tomographic images to correlate with the main lithological units that characterize the study area. The results will be important to enhance the seismic hazard assessment of this complex tectonic region. These images show the ductile Apennine platform (VP = 5.3 km/s) overlaying the brittle Apulian platform (VP = 6.0 km/s) at depth of around 5 km. The central sector of the area shows a clear fold and thrust interface. Along this structure, most of the seismicity occurred, including the strongest event of the sequence (MW 5.0). High VP (>6.8 km/s) and high VP/VS (>1.9) patterns, intersecting the southern edge of this western seismogenic volume, have been interpreted as water saturated rocks, in agreement with similar geological context in the Apennines. These fluids could have played a role in nucleation and development of the seismic sequence. A recent study revealed the occurrence of clusters of earthquakes with similar waveforms along the same seismogenic volume. The hypocenters of these cluster events have been compared with the events re-located in this work. Jointly, they depict a 10 km × 4 km fault plane, NW-SE oriented, deepening towards SW with a dip angle of 40–45°. Instead, the volume of seismicity responsible for the ML 4.3 earthquake developed as a mainshock-aftershock sequence, occurring entirely within the average-to-low VP/VS Apennine platform. Our results agree with other independent geophysical analyses carried out in this area, and they could significantly improve the actual knowledge of the main lithologic units of this complex tectonic area.

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Section: Tomographic Methods and Inversion Strategymentioning

confidence: 99%

Crustal Structure of the Seismogenic Volume of the 2010–2014 Pollino (Italy) Seismic Sequence From 3D P- and S-Wave Tomographic Images

et al. 2021

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“…We initially identified the accurate absolute locations of the events using a nonlinear global approach (NonLinLoc) 25 in a 3-D velocity model of the Campania-Lucania area 26 27 . Subsequently, we refined the locations by applying a double-difference technique (HypoDD) 28 , which solves the double-difference equations using the singular value decomposition, in the equivalent layer-averaged 1-D velocity model 29 .…”

Section: Methodsmentioning

confidence: 99%

Anatomy of a microearthquake sequence on an active normal fault

Stabile

Satriano

Orefice

et al. 2012

Sci Rep

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The analysis of similar earthquakes, such as events in a seismic sequence, is an effective tool with which to monitor and study source processes and to understand the mechanical and dynamic states of active fault systems. We are observing seismicity that is primarily concentrated in very limited regions along the 1980 Irpinia earthquake fault zone in Southern Italy, which is a complex system characterised by extensional stress regime. These zones of weakness produce repeated earthquakes and swarm-like microearthquake sequences, which are concentrated in a few specific zones of the fault system. In this study, we focused on a sequence that occurred along the main fault segment of the 1980 Irpinia earthquake to understand its characteristics and its relation to the loading-unloading mechanisms of the fault system.

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“…Marzano and the neighboring area, which recorded widespread coseismic ruptures and a large number of secondary geological effects, including landslides, ground cracks, liquefaction, and variations in the discharge rate of major carbonate springs [14]. The area, which was also struck by a seismic sequence with a M L = 4.9 mainshock [85] in 1996, is presently affected by subdued background seismicity with M L ranging between 1 and 3.3 (Figure 5) [4,[86][87][88]. In July 2020, the NW termination of the extensional fault system (in the Rocca San Felice area; location in Figure 2a) was affected by a minor seismic sequence (with maximum M L = 3.0 recorded for two shocks), including 43 events distributed over a NW-SE-trending, narrow, ca.…”

Section: Seismicitymentioning

confidence: 99%

The MS 6.9, 1980 Irpinia Earthquake from the Basement to the Surface: A Review of Tectonic Geomorphology and Geophysical Constraints, and New Data on Postseismic Deformation

2020

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The MS 6.9, 1980 Irpinia earthquake occurred in the southern Apennines, a fold and thrust belt that has been undergoing post-orogenic extension since ca. 400 kyr. The strongly anisotropic structure of fold and thrust belts like the Apennines, including late-orogenic low-angle normal faults and inherited Mesozoic extensional features besides gently dipping thrusts, result in a complex, overall layered architecture of the orogenic edifice. Effective decoupling between deep and shallow structural levels of this mountain belt is related to the strong rheological contrast produced by a fluid-saturated, shale-dominated mélange zone interposed between buried autochthonous carbonates—continuous with those exposed in the foreland to the east—and the allochthonous units. The presence of fluid reservoirs below the mélange zone is shown by a high VP/VS ratio—which is a proxy for densely fractured fluid-saturated crustal volumes—recorded by seismic tomography within the buried autochthonous carbonates and the top part of the underlying basement. These crustal volumes, in which background seismicity is remarkably concentrated, are fed by fluids migrating along the major active faults. High pore fluid pressures, decreasing the yield stress, are recorded by low stress-drop values associated with the earthquakes. On the other hand, the mountain belt is characterized by substantial gas flow to the surface, recorded as both distributed soil gas emissions and vigorous gas vents. The accumulation of CO2-brine within a reservoir located at hypocentral depths beneath the Irpinia region is not only interpreted to control a multiyear cyclic behavior of microseismicity, but could also play a role in ground motions detected by space-based geodetic measurements in the postseismic period. The analysis carried out in this study of persistent scatterer interferometry synthetic aperture radar (PS-InSAR) data, covering a timespan ranging from 12 to 30 years after the 1980 mainshock, points out that ground deformation has affected the Irpinia earthquake epicentral area in the last decades. These ground motions could be a result of postseismic afterslip, which is well known to occur over years or even decades after a large mainshock such as the 23 November 1980, MS 6.9 earthquake due to cycles of CO2-brine accumulation at depth and its subsequent release by Mw ≥ 3.5 earthquakes, or most likely by a combination of both. Postseismic afterslip controls geomorphology, topography, and surface deformation in seismically active areas such as that of the present study, characterized by ~M 7 earthquakes. Yet, this process has been largely overlooked in the case of the 1980 Irpinia earthquake, and one of the main aims of this study is to fill such the substantial gap of knowledge for the epicentral area of some of the most destructive earthquakes that have ever occurred in Italy.

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3D tomographic imaging of the southern Apennines (Italy): A statistical approach to estimate the model uncertainty and resolution

Cited by 10 publications

References 51 publications

Crustal Structure of the Seismogenic Volume of the 2010–2014 Pollino (Italy) Seismic Sequence From 3D P- and S-Wave Tomographic Images

Crustal Structure of the Seismogenic Volume of the 2010–2014 Pollino (Italy) Seismic Sequence From 3D P- and S-Wave Tomographic Images

Anatomy of a microearthquake sequence on an active normal fault

The MS 6.9, 1980 Irpinia Earthquake from the Basement to the Surface: A Review of Tectonic Geomorphology and Geophysical Constraints, and New Data on Postseismic Deformation

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