Quick regional centroid moment tensor solutions for the Emilia 2012 (northern Italy) seismic sequence

In May-July 2012, a seismic sequence struck a broad area of the Po Plain Region in northern Italy. The sequence included two Ml >5.5 mainshocks. The first one (Ml 5.9) occurred near the city of Finale Emilia (ca. 30 km west of Ferrara) on May 20 at 02:03:53 (UTC), and the second (Ml 5.8) occurred on May 29 at 7:00:03 (UTC), about 12 km southwest of the May 20 mainshock (Figure 1), near the city of Mirandola. The seismic sequence involved an area that extended in an E-W direction for more than 50 km, and included seven Ml ≥5.0 events and more than 2,300 Ml >1.5 events (http://iside.rm.ingv.it). The focal mechanisms of the main events [Pondrelli et al. 2012, Scognamiglio et al. 2012, this volume] consistently showed compressional kinematics with E-W oriented reverse nodal planes. This sector of the Po Plain is known as a region characterized by slow deformation rates due to the northwards motion of the northern Apennines fold-and-thrust belt, which is buried beneath the sedimentary cover of the Po Plain [Picotti and Pazzaglia 2008, Toscani et al. 2009]. Early global positioning system (GPS) measurements [Serpelloni et al. 2006] and the most recent updates [Devoti et al. 2011, Bennett et al. 2012] recognized that less than 2 mm/yr of SW-NE shortening are accommodated across this sector of the Po Plain, in agreement with other present-day stress indicators [Montone et al. 2012] and known active faults [Basili et al. 2008]. In the present study, we describe the GPS data used to study the coseismic deformation related to the May 20 and 29 mainshocks, and provide preliminary models of the two seismic sources, as inverted from consensus GPS coseismic deformation fields. […]

Section: Introductionmentioning

confidence: 88%

Section: Coseismic Displacement and Fault Modelsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

GPS observations of coseismic deformation following the May 20 and 29, 2012, Emilia seismic events (northern Italy): data, analysis and preliminary models

Serpelloni

Anderlini

Avallone

et al. 2012

“…In May 2012, several medium-large earthquakes impacted on a wide portion of the alluvial plain of northern Italy (Figure 1), belonging to the Lombardy, Veneto and Emilia-Romagna regions. The strongest earth-quake (M L 5.9) occurred close to Finale Emilia, while the second largest one (M L 5.8) took place near Mirandola [Pondrelli et al 2012]. The causative faults belong to the Ferrara Arc thrust system [Bonini et al 2014, DISS Working Group 2015, forming the external portion of the Apennines Chain (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Down-hole geophysical characterization of middle-upper Quaternary sequences in the Apennine Foredeep, Mirabello, Italy

Minarelli

Amoroso

Tarabusi

et al. 2016

The 2012 earthquakes sequence stroke a wide area of the alluvial plain in the Emilia-Romagna Region and triggered a new research interest on the role of the subsurface stratigraphic architecture and petrophysical property distribution in the modulation of the local seismic effects. Few direct shear wave velocity V_S data were however available below the depth of 50m. The only available V_S measurements were obtained from an anticline area, characterized by a reduced stratigraphic thickness and peculiar sedimentary facies, hardly representative of the majority of the alluvial plain subsurface. The study provides the first V_S profile available from middle-upper Quaternary successions deposited into a fast subsiding syncline area of the Apennine Foredeep Basin. The P-wave velocity V_P and the S-wave velocity V_S logs fill in the previous data gap on the geophysical parameters needed for the estimation of the local seismic response. Both V_P and V_S logs were continuously acquired to the depth of 265 m. The log records a velocity increase with depth, punctuated by sharp increases at some stratigraphic discordance surfaces. The value of 800 m/s that characterizes the “seismic bedrock”, as defined by the Italian building code [NTC 2008] was never reached at any depth. The investigated succession records a depositional evolution from deltaic-marine to alluvial plain conditions, punctuated by six glacio-eustatic depositional cycles, developed in Middle-Upper Quaternary times. The stratigraphic units described in the syncline log were correlated at a regional scale, with the thinner anticline succession of Mirandola. Correlatable units deposited into syncline and anticline areas reveal similar shear wave velocity values, supporting the regional extrapolation of the measured values.

“…The thrust faulting focal mechanisms of the main shocks and the strongest aftershocks show fault planes with E-W, ENE-WSW, and WNW-ESE orientations [Pondrelli et al 2012, Scognamiglio et al 2012, compatible with the approximately N-S direction of the compression in the area [Montone et al 2012].…”

Section: Introductionmentioning

confidence: 87%

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

Alessio

Alfonsi

Brunori

et al. 2012

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/). […]