Geological evidence for strong historical earthquakes in an “aseismic” region: The Pollino case (Southern Italy)

Michetti, Alessandro Maria; Ferreli, Luca; Serva, Leonello; Vittori, E.

doi:10.1016/s0264-3707(97)00018-5

Cited by 66 publications

(59 citation statements)

References 17 publications

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“…The major mapped faults of the region are the Mercure Basin fault in the northern part of the Pollino range, the Pollino fault running WNW-ESE parallel to the mountain chain, the Castrovillari fault which trends NNW-SSE and the approximately N-S trending Civita fault, both branching off the Pollino fault (Cinti et al 1997(Cinti et al , 2002Michetti et al 1997;Papanikolaou & Roberts 2007;Basili et al 2008;Frepoli et al 2011). The Mercure Basin fault in the north and the system of faults in the south are located in two pull-apart basins of the western sector of the Pollino range, the Mercure basin and the Morano-Castrovillari basin, respectively (Martini et al 2001).…”

Section: O N I a N S E A I O N I A N S E A C A La B R Ia C A La B Rmentioning

confidence: 99%

“…On 1998 September 9, a M w = 5.6 normal faulting event 'reactivated' seismically the northern part of the Mercure basin (Arrigo et al 2006;Brozzetti et al 2009). The Pollino and Castrovillari faults have been silent, despite the fact that palaeoseismological investigations on both faults suggest at least four M > 6 events occurred within a few thousand years (Cinti et al 1997;Michetti et al 1997). The lack of large earthquakes rank the region as one of the most prominent seismic gaps in the Italian peninsula (Valensise & Guidoboni 2000).…”

Section: O N I a N S E A I O N I A N S E A C A La B R Ia C A La B Rmentioning

confidence: 99%

“…They also proposed this structure as the fault activated by the September 1998 M w 5.6 event. Given, however, the complicated and scarce surface expression of these faults and the lack of seismic activity associated with them, the rank of the master fault in the southern part of Pollino range is still debated (Michetti et al 1997;Cinti et al 1997Cinti et al , 2002Spina et al 2009;Palano et al 2011).…”

Section: Tectonic Setting Of the Pollino Range Southern Italymentioning

confidence: 99%

“…On the contrary, the Pollino and Castrovillari faults are still silent although palaeoseismological investigations on both faults suggest several M > 6 events occurred within the last 10 000 yr (Cinti et al 1997(Cinti et al , 2002Michetti et al 1997).…”

Section: Historical Seismicitymentioning

confidence: 99%

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Aseismic transient driving the swarm-like seismic sequence in the Pollino range, Southern Italy

Passarelli¹,

Hainzl²,

Cesca³

et al. 2015

Geophysical Journal International

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S U M M A R YTectonic earthquake swarms challenge our understanding of earthquake processes since it is difficult to link observations to the underlying physical mechanisms and to assess the hazard they pose. Transient forcing is thought to initiate and drive the spatio-temporal release of energy during swarms. The nature of the transient forcing may vary across sequences and range from aseismic creeping or transient slip to diffusion of pore pressure pulses to fluid redistribution and migration within the seismogenic crust. Distinguishing between such forcing mechanisms may be critical to reduce epistemic uncertainties in the assessment of hazard due to seismic swarms, because it can provide information on the frequency-magnitude distribution of the earthquakes (often deviating from the assumed Gutenberg-Richter relation) and on the expected source parameters influencing the ground motion (for example the stress drop). Here we study the ongoing Pollino range (Southern Italy) seismic swarm, a long-lasting seismic sequence with more than five thousand events recorded and located since October 2010. The two largest shocks (magnitude M w = 4.2 and M w = 5.1) are among the largest earthquakes ever recorded in an area which represents a seismic gap in the Italian historical earthquake catalogue. We investigate the geometrical, mechanical and statistical characteristics of the largest earthquakes and of the entire swarm. We calculate the focal mechanisms of the M l > 3 events in the sequence and the transfer of Coulomb stress on nearby known faults and analyse the statistics of the earthquake catalogue. We find that only 25 per cent of the earthquakes in the sequence can be explained as aftershocks, and the remaining 75 per cent may be attributed to a transient forcing. The b-values change in time throughout the sequence, with low b-values correlated with the period of highest rate of activity and with the occurrence of the largest shock. In the light of recent studies on the palaeoseismic and historical activity in the Pollino area, we identify two scenarios consistent with the observations and our analysis: This and past seismic swarms may have been 'passive' features, with small fault patches failing on largely locked faults, or may have been accompanied by an 'active', largely aseismic, release of a large portion of the accumulated tectonic strain. Those scenarios have very different implications for the seismic hazard of the area.

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Section: O N I a N S E A I O N I A N S E A C A La B R Ia C A La B Rmentioning

confidence: 99%

Section: O N I a N S E A I O N I A N S E A C A La B R Ia C A La B Rmentioning

confidence: 99%

Section: Tectonic Setting Of the Pollino Range Southern Italymentioning

confidence: 99%

Section: Historical Seismicitymentioning

confidence: 99%

See 2 more Smart Citations

Aseismic transient driving the swarm-like seismic sequence in the Pollino range, Southern Italy

Passarelli¹,

Hainzl²,

Cesca³

et al. 2015

Geophysical Journal International

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“…This area has been struck by two disruptive earthquakes in 1561 and 1857, but it is not characterized by conclusive geological evidence as far as active tectonics is concerned. Actually, the gap in seismogenic fault-recognition interests wide sectors of the southern Apenninic chain, from the carbonate massif of Matese to the N (N-Matese fault: Galli and Galadini 2003) to the carbonate massif of Pollino to the S (Pollino fault: Michetti et al 1997;Cinti et al 2002;Figs. 1, 2a).…”

Section: Introductionmentioning

confidence: 99%

Late Holocene earthquakes in southern Apennine: paleoseismology of the Caggiano fault

Galli

Bosi

Piscitelli

et al. 2006

Int J Earth Sci (Geol Rundsch)

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Although southern Apennines are characterized by the strongest crustal earthquakes of centralwestern Mediterranean region, local active tectonics is still poorly known, at least for seismogenic fault-recognition is concerned. Research carried out in the Maddalena Mts. (southeast of Irpinia, the region struck by the M w =6.9, 1980 earthquake) indicates historical ruptures along a 17-km-long, N120°normal fault system (Caggiano fault). The system is characterized by a bedrock fault scarp carved in carbonate rocks, which continues laterally into a retreating and eroded smoothed scarp, affecting the clayey-siliciclastic units, and by smart scarps and discontinuous free-faces in Holocene cemented slope-debris and in modern alluvial fan deposits. The geometry of the structure in depth has been depicted by means of electrical resistivity tomography, while paleoseismic analysis carried out in three trenches revealed surface-faulting events during the past 7 ky BP ( 14 C age), the latest occurred in the past 2 ky BP ( 14 C age) and, probably, during/after slopedebris deposition related to the little ice age ($1400-1800 A.D.). Preliminary evaluation accounts for minimum slip rates of 0.3-0.4 mm/year, which is the same order of rates estimated for many active faults along the Apennine chain. Associated earthquakes might be in the order of M w =6.6, to be compared to the historical events occurred in the area (e.g., 1561 and 1857 p.p. earthquakes).

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Lithospheric fault and kinematic decoupling of the Apennines system across the Pollino range

Chiarabba

Agostinetti

Bianchi

2016

Geophysical Research Letters

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A persistent seismic gap is hypothesized in the Pollino area (southern Italy), at the boundary between the Apennines and the Calabrian arc. Presently, seismic swarms are active in the gap area, creating concerns for possible future large earthquakes. In this study, we model the deep Earth structure across the Pollino range to give new insights on the kinematics and tectonics of this enigmatic area. Migrated receiver function profiles show a subvertical lithospheric discontinuity, delineated by an abrupt change in Moho depth and mantle fabrics across the range. The lithospheric‐scale discontinuity bounds the area of earthquake swarm activity and likely decouples the delamination‐related extension of the Apennines from the extensional collapse of the Calabrian fore arc. This large‐scale discontinuity implies that the normal faults are segmented across the range, limiting the lateral extent of faults where future earthquakes might occur.

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Geological evidence for strong historical earthquakes in an “aseismic” region: The Pollino case (Southern Italy)

Cited by 66 publications

References 17 publications

Aseismic transient driving the swarm-like seismic sequence in the Pollino range, Southern Italy

Aseismic transient driving the swarm-like seismic sequence in the Pollino range, Southern Italy

Late Holocene earthquakes in southern Apennine: paleoseismology of the Caggiano fault

Lithospheric fault and kinematic decoupling of the Apennines system across the Pollino range

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