In the months of May and June 2012, the central part of the Po Valley was the scene of a seismic sequence that caused victims and extensive damage. In addition to the effects on buildings and infrastructures, the events caused very significant geological effects on the natural environment. We talked about it with Maurizio Pignone, an INGV geologist who told us what happened and what the organization has done a decade later.
Maurizio, what characteristics did the main shocks of the 2012 seismic sequence have?
The main shock, with a local magnitude of 5.9, occurred on 20 May at 04:03 about 30 kilometers west of Ferrara, but in the following minutes and hour 11 events with a magnitude greater than 4 were recorded. day there was a total of 16 earthquakes of magnitude between 4 and 5, with epicenters in the municipalities of Mirandola, San Felice sul Panaro and Finale Emilia. A few days later, on May 29, a second strong earthquake occurred with a local magnitude of 5.8 and an epicenter about 20 km west of the first main shock.
The collapses caused dozens of victims and hundreds of injured. Furthermore, the damage to the artistic heritage and to civil, industrial and rural buildings was very serious.
What kind of seismic sequence was it?
It was a seismic sequence with different phases of activity. The first, characterized by a high number of earthquakes per day, had peaks of over 20 events on 29 and 300 May and ended at the end of June 2012. A second phase followed from July to October, then a third with an ever decreasing number of seismic events. This trend is clearly evident in the recently published among.
Let's talk about the affected area. What are its features?
It is a geologically active and well known area. In the past it had already been affected by some important earthquakes, as in the case of the long and complex sequence of 1570 which had strongly affected the city of Ferrara and the surrounding areas, with shocks that followed one another for many months. Although the epicentral area is characterized by a predominantly flat morphology with altitude variations of a few metres, the subsoil is characterized by a few hundred meters of alluvial deposits which cover the active tectonic structures which form the most advanced offshoots of the northern Apennines. The external sector of the latter is characterized by a compressive tectonics and the structures show evidence of deformation in progress whose characteristics are confirmed by the data of the seismic monitoring networks, by the focal mechanisms of recent earthquakes, by the measurements of the stations belonging to the GPS network , from the stress field data.
Already in the early hours of Sunday 20 May 2012, the teams of technicians and researchers of the INGV Seismic Emergency Response had reached the epicentral area hit by the strong earthquake that occurred during the night. What type of interventions were carried out?
On the same day, the INGV teams proceeded to install the first temporary seismic stations, in order to improve the quality of seismic monitoring and surveillance of the area. The first eight stations were immediately made operational; following the strong quake of 29 May, another four stations were installed in the western and southern part of the area, spatially covering the entire area affected by the sequence.
At the end of these operations, the temporary emergency seismic network consisted of , ten of which transmitted the data in real time to the acquisition center in Rome, immediately contributing to the elaborations that were produced by the seismologists on duty at the Seismic Surveillance Room in Rome. These stations in real-time, together with the other twelve that acquired data only locally, contributed to the dataset which was the subject of numerous subsequent seismological studies.
What were the most relevant surface geological effects observed during the seismic sequence?
The most relevant superficial cosismic geological effects observed during the sequence were fracturing and liquefaction events. The EMERGEO operational group of INGV (https://www.ingv.it/emergeo/ ) immediately went to the site to survey the effects on the natural environment and investigated an area of approximately 1200 square kilometres. Three main types of surface geological effects have been recognised: liquefaction due to overpressure of the aquifers housed within sandy bodies present in the subsoil, liquefaction associated with fracturing (fractures even tens of meters long and finally extensional fracturing with prevalent horizontal separation , without liquefaction effects.Liquefaction, a cosismic effect common in alluvial plains where there are superficial layers of loose sediments that host aquifers confined by impermeable soils, affected the Municipalities of the epicentral area in a widespread way during the two main shocks of 20 and 29.
Recently, the research activities carried out in the Alto Ferrarese area were presented in the Council Chamber of the Municipality of Terre del Reno in Sant'Agostino (FE). What topics were covered?
The meeting, organized by the Civil Protection of the Upper Ferrarese and with the patronage of the INGV, represented an opportunity for sharing and discussion where various issues were addressed, starting from the state of reconstruction of the affected Municipalities, to the description of the salient features of the seismic sequence of 2012 and of the emergency interventions carried out by INGV Operational Groups. We then moved on to the description of the characteristics of the epicentral area and the geophysical characterization of the sedimentary successions. Finally, we discussed how the research carried out can contribute to territorial planning by following the criteria of seismic microzoning.
Finally, in the days following the earthquake of 20 May 2012, INGV decided to open the blog INGVterremoti.com. Where did this decision come from? What kind of contributions can citizens who want to learn more about the 2012 seismic sequence find there?
During this seismic emergency, in addition to the classic information on websites, many people also sought information and updates on social networks which began to develop considerably in those years. Through il we have published quick updates and scientific insights aimed at the population affected by the ongoing seismic emergency. Providing direct and timely information to people affected by a significant seismic sequence both in terms of duration (months/years) and energy released (magnitude) is very important and useful for being able to deal with it correctly. At the same time, this information activity has proved extremely useful for countering fake news and rumorsoften spread during crisis situations. Of the 132 articles published on the INGVterremoti blog in 2012,, all available in the section “EARTHQUAKE IN ITALY” where it is possible to navigate among numerous posts relating to seismic activity and it is possible to find information on the activities carried out by INGV in the epicentral area and further information.
More information and insights on the seismic sequence in the Po Valley in 2012 are available on the INGVterremoti.com blog at the following links:
: