The 2012 Emilia seismic sequence (Northern Italy): Imaging the thrust fault system by accurate aftershock location

Govoni, Aladino; Marchetti, A.; Gori, Pasquale De; Bona, M. Di; Lucente, Francesco Pio; Improta, Luigi; Chiarabba, C.; Nardi, Anna; Margheriti, Lucia; Agostinetti, Nicola Piana; Giovambattista, Rita Di; Latorre, Diana; Anselmi, Mario; Ciaccio, Maria Grazia; Moretti, Milena; Castellano, Corrado; Piccinini, D.

doi:10.1016/j.tecto.2014.02.013

Cited by 76 publications

(86 citation statements)

References 29 publications

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“…On the other hand, as for other seismic sequence in the Apennines, fluids hosted in the folded sedimentary successions could have been involved in modulating the seismicity during the 2012 Emilia sequence (Calderoni et al 2009;Govoni et al 2014). Overpressure-induced effects have been inferred for the Umbria-Marche 1997 seismic sequence in northern Apennines (Miller et al 2004): the structural and seismic response of this sequence supported a scenario where the coseismic release and propagation of high pressure fluids triggered aftershocks by significantly reducing the effective normal stress.…”

Section: Introductionmentioning

confidence: 78%

“…Geological data for the study area reveal the presence of gas and brines hosted in Cretaceous and Miocene terrains as well as evaporites of the Mesozoic-Triassic sequence which may maintain high fluid pressure at depth due to their low permeability (Ventura and Di Giovambattista 2012). Evidence of deep fluids playing a role in the seismic release was also highlighted by Calderoni et al (2009) in Northern Apennines, while Govoni et al (2014), performing a complete analysis by activities for the exploitation and utilization of reservoirs carried out in recent times in the close neighbourhood of the seismic sequence of 2012'' (ICHESE 2014). The attention was particularly focused on the Cavone reservoir but, from the pressure recordings, water injection is found to entail a pressure perturbation acting only locally around the well, since a rapid dissipation of pore pressure is observed during no flow period (ICHESE 2014).…”

Section: Fluid Pressure Estimatementioning

confidence: 91%

“…Several authors attributed the rupture either to a distinct adjacent thrust fault segment (i.e. the Mirandola thrust), located to the west, with a similar mechanism (Scognamiglio et al 2012;Bignami et al 2012;Govoni et al 2014) or to a different patch on the same blind low-angle thrust fault (Cesca et al 2013). Instead, a different interpretation was provided by Tizzani et al (2013), requiring the activation of three different fault segments and a block roto-translation of the Mirandola anticline.…”

Section: Introductionmentioning

confidence: 99%

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The role of fluid migration and static stress transfer in searching connections between the May 2012 Emilia earthquakes through a fully 3D finite element modeling

Volpe

Piersanti

2016

Model. Earth Syst. Environ.

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On May 20 and 29, 2012, two earthquakes struck the Emilia Romagna region (Northern Italy), with similar mechanisms. The proximity in space and time between the two events required to investigate possible triggering effects in terms of stress transfer or fluid migration. Moreover, the debate concerning fluid extraction-injection activities brought to the appointment of an International Commission (ICHESE), for evaluating relationships between the hydrocarbon exploitation and the seismic activity near the focal zone: the ICHESE conclusive report did not exclude the possibility of a triggering effect associated with explorations, although this appears not supported by robust evidences. On the other hand, there is no agreement between published papers addressing classical triggering mechanisms and in this respect an improved analysis based on 3D numerical modeling is a valuable tool to provide new insights and outcomes. To this aim, we built up a 3D model honoring the complexities of the real Earth, to retrieve the slip patterns on both the rupture planes by implementing finite element computed Green's functions in a linear joint inversion scheme of geodetic data. Then, we inspected possible mechanisms which could have contributed to promote the second event, such as Coulomb stress transfer and natural fluid migration. Our findings suggest that both phenomena are not likely to be responsible for the May 29 earthquake, even if fluid migration was found to have a role in facilitating the rupture but without reaching hydrofracturing condition. Nevertheless a suprahydrostatic pore pressure is inferred which could have promoted the reactivation of the thrust fault.

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Section: Introductionmentioning

confidence: 78%

Section: Fluid Pressure Estimatementioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The role of fluid migration and static stress transfer in searching connections between the May 2012 Emilia earthquakes through a fully 3D finite element modeling

Volpe

Piersanti

2016

Model. Earth Syst. Environ.

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“…The seismic sequence evolved along an about 50 km long, east-west-oriented thrust belt, including 8 events with M L ≥ 5 0 [1]. All the events occurred in the alluvial plain of the Po river, in the foredeep of the northern Apennines chain, where the subsoil is composed of Plio-Quaternary sediment layers placed just above the Emilia-Romagna blind thrust system [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Poroelasticity and Fluid Flow Modeling for the 2012 Emilia-Romagna Earthquakes: Hints from GPS and InSAR Data

et al. 2018

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The Emilia-Romagna seismic sequence in May 2012 was characterized by two mainshocks which were close in time and space. Several authors already modeled the geodetic data in terms of the mechanical interaction of the events in the seismic sequence. Liquefaction has been extensively observed, suggesting an important role of fluids in the sequence. In this work, we focus on the poroelastic effects induced by the two mainshocks. In particular, the target of this work is to model the influence of fluids and pore-pressure changes on surface displacements and on the Coulomb failure function (CFF). The fluid flow and poroelastic modeling was performed in a 3D half-space whose elastic and hydraulic parameters are depth dependent, in accordance with the geology of the Emilia-Romagna subsoil. The model provides both the poroelastic displacements and the pore-pressure changes induced coseismically by the two mainshocks at subsequent periods and their evolution over time. Modeling results are then compared with postseismic InSAR and GPS displacement time series: the InSAR data consist of two SBAS series presented in previous works, while the GPS signal was detected adopting a variational Bayesian independent component analysis (vbICA) method. Thanks to the vbICA, we are able to separate the contribution of afterslip and poroelasticity on the horizontal surface displacements recorded by the GPS stations. The poroelastic GPS component is then compared to the modeled displacements and shown to be mainly due to drainage of the shallowest layers. Our results offer an estimation of the poroelastic effect magnitude that is small but not negligible and mostly confined in the near field of the two mainshocks. We also show that accounting for a 3D fault representation with a nonuniform slip distribution and the elastic-hydraulic layering of the half-space has an important role in the simulation results.

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“…Moreover, for the area affected by the 2012 seismic sequence, some studies provide regional velocity models (for example Malagnini et al 2012;Vuan et al 2011;Govoni et al 2014), while others give evidence of the seismic response at some sites within the epicentral area or compare the ground-motion observation with prediction equations for soft soils (Barnaba et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Site response estimation at Mirandola by virtual reference station

Laurenzano

Priolo

Mucciarelli

et al. 2016

Bull Earthquake Eng

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In this paper, we address the issue of evaluating the seismic site response for sites located on large alluvial plains, for which no reference sites can be identified, but some earthquakes can be simultaneously recorded at both surface and depth. In the proposed method, surface and borehole records are firstly used to assess the local 1D velocity model, then a model representing a virtual reference rock site is defined, and finally the site spectral amplification is calculated through numerical modeling. The effectiveness of the method is demonstrated at the site of Mirandola (Italy). This site is located in an area which suffered heavy damage during the seismic sequence that started in Northern Italy with the Mw = 5.8 event on May 20th, 2012. That time, the site hosted an accelerometer of the National Accelerometric Network, which recorded the whole sequence. A new station, named MIRB (MIRandola Borehole), was installed during 2014; it is equipped with three accelerometric sensors deployed at surface, 31 and 126 m depth, respectively. The results of this study evidence that Mirandola is characterized by an amplification level consistent with that of a class-C soil for up to a period of about 0.45 s, while for higher periods, the amplification lays between class-B and C soils.

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The 2012 Emilia seismic sequence (Northern Italy): Imaging the thrust fault system by accurate aftershock location

Cited by 76 publications

References 29 publications

The role of fluid migration and static stress transfer in searching connections between the May 2012 Emilia earthquakes through a fully 3D finite element modeling

The role of fluid migration and static stress transfer in searching connections between the May 2012 Emilia earthquakes through a fully 3D finite element modeling

Poroelasticity and Fluid Flow Modeling for the 2012 Emilia-Romagna Earthquakes: Hints from GPS and InSAR Data

Site response estimation at Mirandola by virtual reference station

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