Seismogenic stress field estimation in the Calabrian Arc region (south Italy) from a Bayesian approach

Totaro, Cristina; Orecchio, B.; Presti, Debora; Scolaro, Silvia; Neri, G.

doi:10.1002/2016gl070107

Cited by 33 publications

(26 citation statements)

References 65 publications

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“…CC BY 4.0 License. than elsewhere in the region (see, among others,Totaro et al, 2016). The stress inversion results 269 obtained in the present study are reported inTable 1and Fig.…”

supporting

confidence: 60%

What seismicity offshore Sicily suggests about lithosphere dynamics and microplate fragmentation models in the Central Mediterranean

Neri

Totaro

Orecchio

et al. 2018

Preprint

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Abstract. We analyze an updated dataset of earthquakes of Southern Italy, focusing in particular on hypocenter locations and seismogenic stress distributions in the southern and eastearn offshores of Sicily, the two sectors of the study region where seismic and geodetic information needed for geodynamic modeling is still poor because of poor geometry of monitoring networks. Using Bayesian non-linear methods for hypocentral locations and hypocenter error estimates we improve the earthquake locations performed by more traditional linearized techniques, and this helps us to make significant progress in the interpretation of seismicity and seismogenic stress distributions especially where seismometric network geometry is more critical. Epicenter maps and hypocenter vertical sections, together with (i) best quality focal mechanisms coming from seismic waveform inversion and (ii) orientations of stress principal axes estimated by inversion of focal mechanisms, help us to better recognize geodynamic engines and plate margin deformation in the study area. NW-trending convergence between Africa and Eurasia is recognized as the main source of tectonic stress in the study region, producing clearly detectable signatures in terms of σ1 orientations also in the offshore sectors of the western Ionian and the Sicily Channel. Seismicity and seismogenic stress tensor highlight nearly uniform compressional dynamics related to plate convergence in the Sicily Channel, in contrast to rifting and microplate divergence proposed in that sector by other investigators. In the western Ionian, seismicity and stress inversion results reveal superposition of convergence-related compression and extensional dynamics. The latter, characterized by minimum compressive stress oriented SW-NE, can be related to a rifting process (opening SW-NE) hypothesized by previous investigators on the basis of marine geophysics analyses performed between the Alfeo-Etna and the Ionian Faults. The seismicity and seismogenic stress detected in the Western Ionian show that assumptions of microplate rigidity in this area made by previous workers when modeling poor geodetic data available can be inappropriate. Our findings indicate that more complex rheologic models should be adopted for reconstruction of tectonic deformation and microplate relative motions in the Central Mediterranean region.

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“…CC BY 4.0 License. than elsewhere in the region (see, among others,Totaro et al, 2016). The stress inversion results 269 obtained in the present study are reported inTable 1and Fig.…”

supporting

confidence: 60%

What seismicity offshore Sicily suggests about lithosphere dynamics and microplate fragmentation models in the Central Mediterranean

Neri

Totaro

Orecchio

et al. 2018

Preprint

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“…They also consider the “Pollino fault” inactive, except in the vicinity of the intersection with the Castrovillari fault. The few available focal mechanisms in this area indicate E‐W extension by N‐S striking faults and are inconsistent with NW striking faults (Totaro et al, ).…”

Section: The Youngest Exposed Apenninic Thrust Faultmentioning

confidence: 93%

The Culmination of an Oblique Time‐Transgressive Arc Continent Collision: The Pollino Massif Between Calabria and the Southern Apennines, Italy

Filice

Seeber

2019

Tectonics

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The Pollino Massif is the most southeastern outcrop of the Apennine core. It marks the transition between Apenninic shortening and extension, respectively, SE and NW of the massif and is also the cusp of a southeastward plunge that characterizes the submerged Apennines. The SE limit of NE‐SW extension merges with the east limit of Tyrrhenian extension in Calabria. This strategic position is expected to transition southeastward in the progressive oblique collision of the Calabrian forearc and Apulia. We test this hypothesis using published results and new field data. The time‐transgressive emergence of basins on the Apennine thrust wedge is quantitatively consistent with the ESE rollback of the Calabrian arc. Specifically, a thrust‐normal slip reversal on a SW dipping fault is responsible for the tectonic collapse that lead to the Mercure Basin along strike NW of the Pollino Massif and to an east‐to‐west reversal of drainage. This reversal is timed by an intermediate stage of trapped internal drainage with Mid‐Pleistocene lacustrine sedimentation, but it may young to SE as the normal displacement on the border fault decreases gradually to SE and vanishes near the apex of the massif. On the SE side of the massif, contractional tectonics persists at least into the Mid‐Pleistocene and likely later, while NE‐SW extension is absent. Prominent normal faults in that area accommodate range‐parallel extension and are coupled with the thrust faults. The combination of longitudinal extension with a counterclockwise rotation of hanging‐wall units and thrust directivity can account for the final setting in the Apennines.

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“…Published GPS measurements and deformation models of the forearc D'Agostino et al, 2011;Kreemer et al, 2014) exhibit rather low strain rates (~10-20 nanostrain/yr). The combination of slow trenchward motion with the lack of thrust faulting mechanisms in the instrumental record (Neri et al, 2009;Presti et al, 2013;Totaro et al, 2016) led some researchers to hypothesize that the Calabrian subduction is no longer active (Monaco et al, 1996;Perouse et al, 2012). Yet different clusters of earthquakes above m = 6 are reported for onshore Calabria (Rovida et al, 2016;Tiberti et al, 2017), that is, for the portion of the forearc lying approximately above the subduction megathrust, in open contrast with the low observed geodetic strain rates.…”

Section: 1002/2017gl076554mentioning

confidence: 99%

“…(a) Seismicity and GPS data. Focal mechanisms for earthquakes of magnitude >2.6 (fromTotaro et al, 2016) are shown in the dashed red polygon (southern Calabria). Outside this area we plot earthquakes with m ≥ 4.5.…”

mentioning

confidence: 99%

A “Geodetic Gap” in the Calabrian Arc: Evidence for a Locked Subduction Megathrust?

Carafa

Kastelic

Bird

et al. 2018

Geophysical Research Letters

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Subduction of old Ionian seafloor beneath the Calabrian Arc (southern Italy) is the geological process with the greatest mass flux in the central Mediterranean, yet its seismogenic behavior is largely obscured. No unambiguous evidence of subduction‐related earthquakes exists in historical times, and local GPS velocities indicate very low strain rates. Nevertheless, the region hosted some of the deadliest normal‐faulting earthquakes of the entire Mediterranean basin. We show that the low strain rates recorded in southern Calabria can be reconciled with the regional vigorous seismic moment release by assuming high interseismic coupling but low seismic coupling of the subduction interface. The alternative scenario of steadily creeping subduction cannot be ruled out but requires the historical seismicity record to be dismissed as unrepresentative. We refer to the peculiar spatial pattern of short‐term strain rates in southern Calabria as a “geodetic gap” resulting from destructive interference between upper‐plate extension and temporary compression due to locking along the subduction interface. Seismic hazard modelers must understand that within such gaps, the long‐term seismic hazard is greater than that suggested by the low geodetic strain rates.

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Seismogenic stress field estimation in the Calabrian Arc region (south Italy) from a Bayesian approach

Cited by 33 publications

References 65 publications

What seismicity offshore Sicily suggests about lithosphere dynamics and microplate fragmentation models in the Central Mediterranean

What seismicity offshore Sicily suggests about lithosphere dynamics and microplate fragmentation models in the Central Mediterranean

The Culmination of an Oblique Time‐Transgressive Arc Continent Collision: The Pollino Massif Between Calabria and the Southern Apennines, Italy

A “Geodetic Gap” in the Calabrian Arc: Evidence for a Locked Subduction Megathrust?

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