Searching for the effects of the May-June 2012 Emilia seismic sequence (northern Italy): medium-depth deformation structures at the periphery of the epicentral area

In 2012, a seismic sequence occurred in the lowlands of the Emilia-Romagna Region (northern Italy), between the borders of the Modena, Ferrara and Bologna Provinces. It consisted of seven mainshocks (5.9 > Ml > 5) that were recorded between May 20 and 29, 2012 [INGV 2012a] and 2,200 minor earthquakes [INGV 2012b]. An interferometric analysis [Bignami et al. 2012, Salvi et al. 2012, this volume] highlighted three main deformation areas, each of which was 12 km wide (from S to N) and 10 km to 20 km long in an ESE-WNW to E-W direction, thus affecting an area of about 600 km2 (Figure 1). Field and aerial geological surveys recorded numerous surficial effects, such as: (i) sediment liquefaction [Crespellani et al. 2012]; (ii) localized ground fissures resembling surficial faulting [Fioravante and Giretti 2012] (Figure 2); (iii) groundwater levels rising up to 400 cm above the local ground level in phreatic wells during the mainshocks (lower values were observed in confined aquifers); and (iv) dormancy of previously known sinkholes [Borgatti et al. 2010, Cremonini 2010a, and references therein]. Some of the observed surface phenomena were previously recorded as coseismic effects during the earthquakes of Ferrara (1570) and Argenta (1624) [Boschi et al. 1995, Galli 2000], together with the early rising of the water level of the Po River in the Stellata section. […]

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Technologies and new approaches used by the INGV EMERGEO Working Group for real-time data sourcing and processing during the Emilia Romagna (northern Italy) 2012 earthquake sequence

Annals of Geophysics ◽

10.4401/ag-6117 ◽

2012 ◽

Vol 55 (4) ◽

Author(s):

Giuliana Alessio ◽

Laura Alfonsi ◽

Carlo Alberto Brunori ◽

Pierfrancesco Burrato ◽

Giuseppe Casula ◽

...

Keyword(s):

Seismic Event ◽

Main Shock ◽

Northern Italy ◽

Earthquake Activity ◽

Seismic Sequence ◽

Time Data ◽

Broad Area ◽

Epicentral Area ◽

Po Plain ◽

Real Time Data

On May 20, 2012, a Ml 5.9 seismic event hit the Emilia Po Plain, triggering intense earthquake activity along a broad area of the Po Plain across the provinces of Modena, Ferrara, Rovigo and Mantova (Figure 1). Nine days later, on May 29, 2012, a Ml 5.8 event occurred roughly 10 km to the SW of the first main shock. These events caused widespread damage and resulted in 26 victims. The aftershock area extended over more than 50 km and was elongated in the WNW-ESE direction, and it included five major aftershocks with 5.1 ≤Ml ≤5.3, and more than 2000 minor events (Figure 1). In general, the seismic sequence was confined to the upper 10 km of the crust. Minor seismicity with depths ranging from 10 km to 30 km extended towards the southern sector of the epicentral area (ISIDe, http://iside.rm.ingv.it/). […]

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Soil-gas survey of liquefaction and collapsed caves during the Emilia seismic sequence

Annals of Geophysics ◽

10.4401/ag-6122 ◽

2012 ◽

Vol 55 (4) ◽

Author(s):

Alessandra Sciarra ◽

Barbara Cantucci ◽

Mauro Buttinelli ◽

Gianfranco Galli ◽

Manuela Nazzari ◽

...

Keyword(s):

Soil Liquefaction ◽

Early Pleistocene ◽

Seismic Sequence ◽

Alluvial Deposits ◽

Epicentral Area ◽

Emilia Romagna Region ◽

External Part ◽

Strength And Stiffness ◽

Soil Measurements ◽

Soil Gas Survey

The epicentral area of the Emilia seismic sequence is located in the Emilia-Romagna Region (northern Italy), 45 km from the city of Modena (Figure 1). This area is sited within thrust-related folds of the Ferrara Arc, which represent the most external part of the northern Apennines. This sector is considered as having been active during late Pliocene to early Pleistocene times [Scrocca et al. 2007] and encompasses also the Mirandola and Ferrara seismogenic sources [e.g., Burrato et al. 2003, Boccaletti et al. 2004, Basili et al. 2008]. The main sedimentary infilling of the Po Plain is represented by Pliocene–Pleistocene alluvial deposits (alternating fluvial sands and clays) that overlie a foredeep clastic sequence, with a total average thickness of 2 km to 4 km [e.g., Carminati et al. 2010]. Soon after the mainshock, several liquefaction phenomena coupled to ground fractures were observed in the epicentral area (e.g., San Carlo, Ferrara). Soil liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. […] Collapsed caves reported in the literature and/or local press [e.g., Febo 1999, Martelli 2002] in the epicentral area were previously investigated by our research group in 2008, with several soil measurements of CO2 and CH4 fluxes. Immediately after the May 20, 2012, mainshock and during the Emilia seismic sequence, the collapsed caves were sampled again to determine any variations in these CO2 and CH4 fluxes. In this survey, newly formed collapsed caves were also found and measured (especially in the northern part of investigated area). […]

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ER3D: a structural and geophysical 3-D model of central Emilia-Romagna (northern Italy) for numerical simulation of earthquake ground motion

Solid Earth ◽

10.5194/se-10-931-2019 ◽

2019 ◽

Vol 10 (3) ◽

pp. 931-949 ◽

Cited By ~ 1

Author(s):

Peter Klin ◽

Giovanna Laurenzano ◽

Maria Adelaide Romano ◽

Enrico Priolo ◽

Luca Martelli

Keyword(s):

Numerical Simulations ◽

Ground Motion ◽

Northern Italy ◽

Peak Ground Velocity ◽

Earthquake Ground Motion ◽

Po River ◽

Epicentral Area ◽

River Bank ◽

Local Seismic Response ◽

D Model

Abstract. During the 2012 seismic sequence of the Emilia region (northern Italy), the earthquake ground motion in the epicentral area featured longer duration and higher velocity than those estimated by empirical-based prediction equations typically adopted in Italy. In order to explain these anomalies, we (1) build up a structural and geophysical 3-D digital model of the crustal sector involved in the sequence, (2) reproduce the earthquake ground motion at some seismological stations through physics-based numerical simulations and (3) compare the observed recordings with the simulated ones. In this way, we investigate how the earthquake ground motion in the epicentral area is influenced by local stratigraphy and geological structure buried under the Po Plain alluvium. Our study area covers approximately 5000 km2 and extends from the right Po River bank to the Northern Apennine morphological margin in the N–S direction, and between the two chief towns of Reggio Emilia and Ferrara in the W–E direction, involving a crustal volume of 20 km thickness. We set up the 3-D model by using already-published geological and geophysical data, with details corresponding to a map at scale of 1:250 000. The model depicts the stratigraphic and tectonic relationships of the main geological formations, the known faults and the spatial pattern of the seismic properties. Being a digital vector structure, the 3-D model can be easily modified or refined locally for future improvements or applications. We exploit high-performance computing to perform numerical simulations of the seismic wave propagation in the frequency range up to 2 Hz. In order to get rid of the finite source effects and validate the model response, we choose to reproduce the ground motion related to two moderate-size aftershocks of the 2012 Emilia sequence that were recorded by a large number of stations. The obtained solutions compare very well to the recordings available at about 30 stations in terms of peak ground velocity and signal duration. Snapshots of the simulated wavefield allow us to attribute the exceptional length of the observed ground motion to surface wave overtones that are excited in the alluvial basin by the buried ridge of the Mirandola anticline. Physics-based simulations using realistic 3-D geomodels show eventually to be effective for assessing the local seismic response and the seismic hazard in geologically complex areas.

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Seismic Performance of Industrial Sheds and Liquefaction Effects During May 2012 Emilia Earthquakes Sequence in Northern Italy

Journal of Earthquake and Tsunami ◽

10.1142/s1793431114500092 ◽

2014 ◽

Vol 08 (02) ◽

pp. 1450009 ◽

Cited By ~ 5

Author(s):

Gian Paolo Cimellaro ◽

Marco Chiriatti ◽

Hwasung Roh ◽

Andrei M. Reinhorn

Keyword(s):

Emergency Response ◽

Working Hours ◽

Northern Italy ◽

Seismic Sequence ◽

Epicentral Area ◽

Existing Structures ◽

Industrial Sites ◽

Emilia Earthquake ◽

Private Homes ◽

Seismic Area

On May 20, 2012 at 2:03 UTC, a Mw 6.1 earthquake occurred in Emilia Region of Northern Italy. The event was preceded by a Ml 4.1 foreshock on May 19, 2012 at 23:13 UTC, and followed by several aftershocks, twenty of them with a magnitude Mw greater than 4. The epicentral area of the seismic sequence covers alluvial lowland that is occupied by both agricultural and urbanized areas. Liquefaction effects were observed in several villages on the west side of Ferrara which were built upon former river beds such as the Reno River. The Emilia seismic sequence resulted in 27 casualties, several of whom were among the workers in the factories that collapsed during working hours, and there was extensive damage to monuments, public buildings, industrial sites and private homes. Almost no municipalities hit by 2012 earthquake were classified as seismic area before 2003; therefore, most of the existing structures had been designed without taking in account the seismic actions. The main aims of MCEER field mission was to document the emergency response and the most common damage mechanisms of industrial sheds during Emilia earthquake sequence which are shown and discussed in detail.

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ER3D: a structural and geophysical 3D model of central Emilia-Romagna (Northern Italy) for numerical simulation of earthquake ground motion

10.5194/se-2019-1 ◽

2019 ◽

Author(s):

Peter Klin ◽

Giovanna Laurenzano ◽

M. Adelaide Romano ◽

Enrico Priolo ◽

Luca Martelli

Keyword(s):

Numerical Simulations ◽

Ground Motion ◽

High Performance ◽

3D Model ◽

Northern Italy ◽

Peak Ground Velocity ◽

Earthquake Ground Motion ◽

Po River ◽

Epicentral Area ◽

Local Seismic Response

Abstract. During the 2012 seismic sequence of Emilia region (Northern Italy), the earthquake ground motion in the epicentral area featured longer duration and higher velocity than those estimated by empirical-based prediction equations typically adopted in Italy. In order to explain these anomalies, we (1) build up a structural and geophysical 3D digital model of the crustal sector involved in the sequence, (2) reproduce the earthquake ground motion at some seismological stations through physics-based numerical simulations and (3) compare the observed recordings with the simulated ones. In this way we investigate how the earthquake ground motion in the epicentral area is influenced by local stratigraphy and geological structure buried under the Po Plain alluvium. Our study area covers approximately 5000 km2 and extends from the Po river right bank to the Northern Apennines morphological margin in N-S direction, and between the two chief towns of Reggio Emilia and Ferrara in W-E direction, involving a crustal volume with 20 km of thickness. We set up the 3D model by using already published geological and geophysical data, with a detail corresponding to a map at scale 1:250 000. The model depicts the stratigraphic and tectonic relationships of the main geological formations, the known faults and the spatial pattern of the seismic properties. Being a digital vector structure, the 3D model can be easily modified or refined locally for future improvements or applications. We exploited high performance computing to perform numerical simulations of the seismic wave propagation in the frequency range up to 2 Hz. In order to get rid of the finite source effects and validate the model response, we choose to reproduce the ground motion related to two moderate-size aftershocks of the 2012 Emilia sequence that were recorded by a large number of stations. The obtained solutions compare very well to the recordings available at about 30 stations, in terms of peak ground velocity and signal duration. Snapshots of the simulated wavefield allow us to explain the exceptional length of the observed ground motion as due to surface waves overtones that are excited in the alluvial basin by the buried ridge of the Mirandola anticline. Physics-based simulations using realistic 3D geo-models show eventually to be effective for assessing the local seismic response and the seismic hazard in geologically complex areas.

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The May 2012 Emilia (Italy) earthquakes: preliminary interpretations on the seismogenic source and the origin of the coseismic ground effects

Annals of Geophysics ◽

10.4401/ag-6171 ◽

2012 ◽

Vol 55 (4) ◽

Author(s):

Alberto Pizzi ◽

Vittorio Scisciani

Keyword(s):

Seismic Reflection ◽

Field Survey ◽

Epicentral Distance ◽

Northern Italy ◽

Seismic Reflection Profile ◽

Epicentral Area ◽

Preliminary Model ◽

Seismogenic Source ◽

Emilia Romagna Region ◽

Ground Effects

On May 20, 2012, a Ml 5.9 earthquake (T1) occurred in the Emilia-Romagna Region of northern Italy. This was preceded by a Ml 4.1 foreshock on May 19, 2012, and followed by several aftershocks, including two Ml 5.1 events, both on the same day. On May 29, 2012, a second strong event of Ml 5.8 (T2) hit the same region, with its epicenter ca. 12 km to the WSW of the first mainshock, T1. The epicentral area of the seismic sequence covers an alluvial lowland that is occupied by both agricultural and urbanized areas, and there were 17 casualties and about 14,000 people left homeless. […] In the present study, we provide a preliminary model of the seismogenic source(s) responsible for the two mainshocks, by comparing the seismic reflection profile interpretation with the available seismological and interferometric data. Furthermore, we show the coseismic ground effects that were observed in the epicentral area during two field survey campaigns: the first conducted after the May 20, 2012, event and the second soon after the May 29, 2012, earthquake, when several sites were revisited to observe the occurrence of newly formed or 're-activated' liquefaction features. Hence, we discuss the origin and location of the coseismic features observed in the context of the local geological–geomorphological setting and with respect to the epicentral distance. Finally, we provide our interpretation for the question: "Why did the mainshock ruptures not break the surface?" […]

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Liquefaction phenomena along the paleo-Reno River caused by the May 20, 2012, Emilia (northern Italy) earthquake

Annals of Geophysics ◽

10.4401/ag-6147 ◽

2012 ◽

Vol 55 (4) ◽

Author(s):

Giorgos Papathanassiou ◽

Riccardo Caputo ◽

Dimitra Rapti-Caputo

Keyword(s):

Structural Damage ◽

Northern Italy ◽

Seismic Profiles ◽

Ground Acceleration ◽

Po River ◽

Maximum Acceleration ◽

Epicentral Area ◽

Industrial Buildings ◽

Moderate Earthquake ◽

Dense Grid

On the May 20, 2012 (04:03:52 local time; 02:03:52 UTC), a moderate earthquake (Ml 5.9) [Scognamiglio et al. 2012, this volume] with a focal mechanism showing E-W-trending, S-dipping, reverse-faulting occurred in the eastern sector of the alluvial plain of the Po River, close to the border between the Regions of Emilia-Romagna and Lombardia (northern Italy). The tectonic structure is completely blind, but it was well known from a dense grid of seismic profiles for hydrocarbon explorations [e.g., Pieri and Groppi 1981, Toscani et al. 2009]. The earthquake triggered extensive liquefaction-induced ground effects at the surface, and caused severe structural damage to nonreinforced masonry and precast industrial buildings within the broader epicentral area. The hypocenter was at 44.89 ˚N, 11.23 ˚E, at a depth of 6.3 km [Scognamiglio et al. 2012], while the maximum acceleration was recorded in Mirandola, with peak ground acceleration 310 cm/s2 and 264 cm/s2 along the vertical and horizontal components, respectively [Bozzoni et al. 2012, this volume]. In this report, we focus on a zone including the Sant'A-gostino, San Carlo and Mirabello villages (west Ferrara Province), which were built along an abandoned reach of the Reno River and where liquefaction phenomena were particularly diffuse, with very intense local effects. […]

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Preliminary results from EMERSITO, a rapid response network for site-effect studies

Annals of Geophysics ◽

10.4401/ag-6153 ◽

2012 ◽

Vol 55 (4) ◽

Author(s):

Paola Bordoni ◽

Riccardo M. Azzara ◽

Fabrizio Cara ◽

Rocco Cogliano ◽

Giovanna Cultrera ◽

...

Keyword(s):

Working Hours ◽

Site Effect ◽

Reverse Fault ◽

Seismic Sequence ◽

Po River ◽

Response Network ◽

Emilia Romagna Region ◽

The Many ◽

Private Homes ◽

The Village

On May 20, 2012, at 02:03 UTC, a Ml 5.9 reverse-fault earthquake occurred in the Emilia-Romagna region, northern Italy, at a hypocentral depth of 6.3 km (http://iside.rm.ingv.it/), close to the cities of Modena and Ferrara in the plain of the Po River. The epicenter was near the village of Finale Emilia where macroseismic intensity was assessed at 7 EMS98 [Tertulliani et al. 2012, this issue], while the closest accelerometric station, MRN, located less than 20 km west-ward at Mirandola (Figure 1) recorded peaks of ground accelerations of about 300 cm/s2 (www.protezionecivile.gov.it/resources/cms/documents/Report_DPC_1_Emilia_EQSd.pdf). The mainshock triggered liquefaction phenomena a few kilometers eastwards of the epicenter, around the village of San Carlo. On the same day, two other shocks of Ml 5.1 followed (02:07, 13:18 GMT; http://iside.rm.ingv.it/). On May 29, 2012, at 07:00 UTC another Ml 5.8 earthquake hit the region (http://iside.rm.ingv.it/), with the epicenter close to the village of Mirandola (Figure 1). Three other strong aftershocks occurred afterwards, of Ml 5.3 (May 29, at 10:55), Ml 5.2 (May 29, at 11:00) and Ml 5.1 (June 3, at 19:20). For a detailed description of the seismic sequence, see Moretti et al. [2012], Scognamiglio et al. [2012], and Massa et al. [2012], in this issue. The Emilia seismic sequence resulted in 25 casualties, several of whom were among the workers in the many factories that collapsed during working hours, and there was extensive damage to monuments, public buildings, industrial sites, and private homes. […]

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Effects on the groundwater levels of the May-June 2012 Emilia seismic sequence

Annals of Geophysics ◽

10.4401/ag-6139 ◽

2012 ◽

Vol 55 (4) ◽

Author(s):

Marco Marcaccio ◽

Giovanni Martinelli

Keyword(s):

Monitoring Network ◽

Automatic Monitoring ◽

Water Levels ◽

Sudden Increase ◽

Seismic Sequence ◽

Epicentral Area ◽

Groundwater Levels ◽

The Past ◽

Set Up ◽

Romagna Area

A variety of phenomena were observed in the groundwaters in concomitance with the May-June 2012 seismic sequence that occurred in the Emilia Romagna area. In particular, phreatic wells close to the epicentral area were affected by a sudden increase in water level of up to 4 m. In some cases, the sands of aquifers were ejected outside wells, and >700 liquefaction phenomena were recorded [Bertolini and Fioroni 2012, this volume]. Some automatic stations of the regional well network recorded variations in well levels. These data can be considered useful to understand the relationships between seismic events and the local groundwaters [see also Italiano et al. 2012, this volume]. […] In 1976, a regional network composed of 330 wells was set up with the purpose of monitoring the groundwater levels using manual techniques. These data have been used for environmental purposes and for water management. In recent years, the monitoring network managed by Agenzia Regionale Prevenzione e Ambiente (ARPA) has increased the number of wells (to about 600), and chemical analyses are also periodically carried out for environmental monitoring activities. In the past three years, an automatic monitoring network composed of 40 stations was set up and this has allowed the monitoring of the water levels and the temperatures, at a rate of one measure per hour, and to broadcast the data to the host center located in Bologna. […]

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