Recent seismicity and crustal stress field in the Lucanian Apennines and surrounding areas (Southern Italy): Seismotectonic implications

A new dataset of first P-wave arrival times is used to derive the 3D tomographic model of the Campania-Lucania region in the southern Apennines (Italy). We address the issue related to the non-uniqueness of the tomographic inversion solution through massive numerical experimentation based on the global exploration of the model parameter space starting from a large variety of physically plausible initial models. The average of all the realizations is adopted as the best-fit solution and the uncertainty of the model parameters is studied using a statistical approach based on a Monte Carlo-type analysis. How the uncertainty in the initial model, earthquake locations, and data influences the inversion result is studied by considering separately the individual effects. Checkerboard tests are performed to estimate the resolving power of the dataset. Re-located seismicity in a reliable new 3D tomographic model allows us to correlate the earthquake distribution with the main seismogenic structures present in the area.

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“…This value is consistent with the results obtained by other authors in the same area (Maggi et al, 2009).…”

Section: 1 1 D S T a R T I N G M O D E L Ssupporting

confidence: 94%

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

et al. 2010

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“…At present, the main northeast-southwest anti-apenninic extensional stress field is the dominant stress field of the central part of the Pollino range. This has been confirmed by geodetic measurements (Serpelloni et al 2005;Ferranti et al 2014) and stress tensor inversion of focal mechanisms solutions (Maggi et al 2009;Frepoli et al 2011;Palano et al 2011;Totaro et al 2013). Therefore, on the local scale the inland ongoing extensional stress field within the Pollino range may be accommodated by basin-forming normal faulting (Martini et al 2001).…”

Section: Tectonic Setting Of the Pollino Range Southern Italymentioning

confidence: 53%

“…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%

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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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“…The analyzed south Apennine area between the Allocton and the foredeep is characterized by an active extensional regime, according to Montone et al [19,28] and Maggi et al [29]. On the basis of the few fault-planes data available in the analyzed region, it was not possible to clearly determine whether the stress field in the foredeep is normal (like in the Apennine belt) or strike slip (like in the foreland).…”

Section: Initialization Processmentioning

confidence: 99%

How to Approach Subsidence Evaluation for Marginal Fields: A Case History

Benetatos¹,

Rocca²,

Sacchi³

et al. 2015

TOPEJ

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This paper presents the evaluation of the subsidence potentially induced by underground storage of natural gas in a marginal depleted field located in Southern Italy. The critical aspect of the study was the lack of data because economic and logistic reasons had restricted data acquisition at the regional scale to perform a geomechanical study. This limitation was overcome by accurately gathering the available data from public sources so that the geometry of a largescale 3D model could be defined and the formations properly characterized for rock deformation analysis. Well logs, seismic data and subsidence surveys at the regional scale, available in open databases and in the technical literature, were integrated with the available geological and fluid-flow information at the reservoir scale. First of all, a 3D geological model, at the regional scale, incorporating the existing model of the reservoir was developed to describe the key features of a large subsurface volume while preserving the detail of the storage reservoir. Then, a regional geomechanical model was set up for coupled mechanic and fluid-flow analyses. The stress and strain evolution and the associated subsidence induced in the reservoir and surrounding formations by historical primary production as well as future gas storage activities were investigated. Eventually, the obtained results were validated against the measurements of ground surface movements available from the technical literature for the area of interest, thus corroborating the choice of the most critical geomechanical parameters and relevant deformation properties of the rocks affecting subsidence.

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Recent seismicity and crustal stress field in the Lucanian Apennines and surrounding areas (Southern Italy): Seismotectonic implications

Cited by 33 publications

References 32 publications

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

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

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

How to Approach Subsidence Evaluation for Marginal Fields: A Case History

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