Ground Effects during the 9 September 1998, Mw = 5.6 Lauria Earthquake and the Seismic Potential of the "Aseismic" Pollino Region in Southern Italy

Michetti, Alessandro Maria; Ferreli, Luca; Esposito, E.; Porfido, Sabina; Blumetti, Anna Maria; Vittori, E.; Serva, Leonello; Roberts, Gerald

doi:10.1785/gssrl.71.1.31

Cited by 90 publications

(64 citation statements)

References 18 publications

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“…This was first recognized by Omori at the beginning of the last century (Omori 1909) and further detailed through historical investigation by referring to this lack of large events as the 'Pollino seismic gap' (Valensise & Guidoboni 2000). However, on the 1998 September 9, a M w = 5.6 normal fault event 'reactivated' the Mercure Basin fault (Michetti et al 2000;Arrigo et al 2006;Maggi et al 2009) having a geometry compatible with the geologically mapped fault (Basili et al 2008). …”

Section: Historical Seismicitymentioning

confidence: 99%

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: Historical Seismicitymentioning

confidence: 99%

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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“…1), where a seismic gap was previously hypothesized by paleoseismological evidence associated with the lack of major earthquakes in historical catalogs (Michetti et al, 2000;Cinti et al, 2002). Seismic activity is in progress at the time of writing of this paper (December 2012) after quite a disturbing long-term acceleration of earthquake rate and strain release (Fig.…”

Section: Introductionmentioning

confidence: 77%

“…Between Calabria and the southern Apennines, the Pollino area has been affected only by moderate seismicity in the last centuries, as witnessed by historical and recent catalogs reporting earthquakes of maximum magnitude in the range 5.5-6, such as those, which occurred in 1693, 1708, and 1998 (see e.g., Galli et al, 2001;Arrigo et al, 2006;Rovida et al, 2011). On the other hand, paleoseismological investigations have identified in the southern Pollino area at least two surface-faulting events between the sixth and fifteenth centuries A.D. relatable to earthquakes of magnitude 6.5-7 (Michetti et al, 2000;Cinti et al, 2002; trench site locations are indicated in Fig. 2).…”

Section: Geological Settingmentioning

confidence: 99%

“…The structural and seismotectonic setting of the Pollino area is quite intricate and different views have been proposed by different authors (see, among others, Michetti et al, 2000;Catalano et al, 2004;Database of Individual Seismogenic Sources [DISS] Working Group, 2010;Spina et al, 2011). Although normal mechanisms on northwest-trending structures represent the most diffuse faulting style, diversely oriented structures and different mechanisms are also reported, such as left-lateral strike-slip kinematics in the west-northwest-trending Pollino fault zone (PFZ) on the southern side of the Massif (Van Dijk et al, 2000;Catalano et al, 2004;Spina et al, 2011;see Fig.…”

Section: Geological Settingmentioning

confidence: 99%

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The Ongoing Seismic Sequence at the Pollino Mountains, Italy

Totaro

Presti

Billi

et al. 2013

Seismological Research Letters

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“…In the same way, local landslides have been reported to occur from intensities of V-VI, but found to be common for VI-VII (Serva, 1994;Esposito et al, 1997). Finally recent moderate earthquakes (Ms 5-6) in south Italy (Michetti et al, 2000) and Greece (Mariolakos et al, 1998) indicate that similar pop-up like features and discrete landslides can be produced by intensities of VI-VII MSK. However, the level of destruction recorded in the architectural relicts of Baelo Claudia let to infer a peak intensity of IX-X MSK at least in the lower coastal sector of the city.…”

Section: Expected Ground-site Response From Local Seismicitymentioning

confidence: 99%

Archaeoseismic record at the ancient Roman City of Baelo Claudia (Cádiz, south Spain)

et al. 2005

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This study represents the first paleoseismic approach in Spain in which archaeological remains are considered. The ancient Roman city of Baelo Claudia (1st-4th centuries AD), located at the axial zone of the Gibraltar Strait (Cadiz, south Spain), contains abundant disrupted architectural relics and ground collapses (i.e. landsliding, liquefacion) probably related to historic earthquake damage of intensity IX-X MSK. The archaeological stratigraphy of the city evidence two major episodes of abrupt city destruction bracketed in AD 40-60 and AD 350-395 separated by an intervening horizon of demolition for city rebuilding, otherwise characteristic for many earthquake-damaged archaeological sites in the Mediterranean. The second episode led the eventual city abandonment, and it is evidenced by good examples of column collapse, distortion, failure and breakdown of house and city walls, and pavement warping and disruptions documented during different archaeological excavations, which can be catalogued as secondary coseismic effects. Main damaged relicts observable today are the set of pop-up like arrays and warping developed in the ancient Roman pavement. Their analysis indicate an anomalous westwards ground displacement oblique to the main gentle southward slope of the topography, as also evidence failures, collapses and breakdown of walls and columns, suggesting that stress acted in a broad SW-NE/WSW-ENE orientation consistent whit the expectable motion along the largest NE-SW strike-slip faults of the zone, which in turn can be catalogued as seismic sources of moderate events (ca. 5 mb). Major disruptions and city abandonment were hesitantly related to relatively far strong earthquakes occurred during the late 4th century AD in the Mediterranean or western coast of Iberia by Menanteau et al. [Menanteau, L., Vanney, J.R., Zazo, C., 1983. Belo II : Belo et son environment (Detroit de Gibraltar), Etude physique d'un site antique. Pub. Casa de Velazquez, Serie Archeologie 4., Ed. Broccard, París.]. However, this study indicates that the occurrence of close moderate earthquakes jointly with the unstable character of the ground at the zone (site effect) is a more reliable hypothesis to explain the observed deformations. D

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Ground Effects during the 9 September 1998, Mw = 5.6 Lauria Earthquake and the Seismic Potential of the "Aseismic" Pollino Region in Southern Italy

Cited by 90 publications

References 18 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

The Ongoing Seismic Sequence at the Pollino Mountains, Italy

Archaeoseismic record at the ancient Roman City of Baelo Claudia (Cádiz, south Spain)

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