Introduction

Paolo Clemente, Massimo Forni, Alessandro Martelli

(download pdf)

On May 22nd, 2012, at 04:03 local time, an earthquake of L = 5.9, according to the INGV (Italian National Institute of Geophisics and Vulcanology) estimation, struck the Pianura Padana Emiliana, Italy. The hypocenter was only 6 km deep, resulting in the consequent strong effects observed on the surface. The epicenter was located at Latitude 44.89° N and Longitude 11.12° E, in a sparsely inhabited area between the towns of Mirandola, Finale Emilia, Poggio Rusco and Bondeno (Fig. 1).

 

FIGURE  1

IntroductionFig1.jpg


Source: ENEA from INGV data

 

The main event was preceded by a shock at 01:13 (ML = 4.1) and followed by a number of events of magnitude > 4.0. In particular, an earthquake of ML = 4.9 occurred just one hour after the main event, at 05:02, and another of ML = 5.1 occurred at 15:18. The most significant events until 15:21 (Italian time) on 20/05 are listed in Table 1.

TABLE 1

Date

Time (UTC)

Lat

Lon

Depth (km)

ML

2012/05/19

23:13:27

44.898

11.258

6.2

4.1

2012/05/20

02:03:52

44.89

11.23

6.3

5.9

2012/05/20

02:11:46

44.84

11.37

7.8

4.3

2012/05/20

02:12:42

44.82

11.22

20.4

4.3

2012/05/20

02:35:37

44.88

11.55

10

4.0

2012/05/20

02:39:10

44.89

11.26

5.2

4.0

2012/05/20

03:02:50

44.86

11.1

10

4.9

2012/05/20

09:13:21

44.879

11.241

3.1

4.2

2012/05/20

13:18:02

44.831

11.49

4.7

5.1

2012/05/20

13:21:06

44.882

11.383

2.4

4.1

2012/05/20

17:37:14

44.88

11.38

3.2

4.5


Source: INGV

 

The epicenters of the various shocks stretched over an area of about 40 km in W-E direction. The strongest earthquake of the sequence was due to a phenomenon of active compression in North-South direction, related to the thrust of the northern Apennines to the North, above the Adriatic / African plate. It is a complex system of faults (Fig. 2).

FIGURE 2

IntroductionFig2.jpg


Source: Courtesy by Faccenna et al.

 

In the following days, many events occurred, some of magnitude greater than 4.0 (Table 2), while an important new sequence was recorded on May 29th, when at 09:00 (Italian time) an event of ML = 5.8 was recorded with epicenter between the towns of Medolla, Mirandola and Cavezzo. It was followed by numerous other events with a magnitude > 4.0, two of which > 5.0 (Table 3).

TABLE 2

Date

Time (UTC)

Lat

Lon

Depth (km)

L

2012/05/21

17:37:14

44.851

11.348

10.4

4.1

2012/05/23

21:41:18

44.868

11.251

4.8

4.3

2012/05/25

13:14:05

44.883

11.108

10

4.0

2012/05/27

18:18:45

44.882

11.158

4.7

4.0

st and 27th, 2012
Source: INGV


TABLE 3

Date

Time (UTC)

Lat

Lon

Depth (km)

L

2012/05/29

07:00:03

44.851

11.086

10.2

5.8

2012/05/29

07:07:21

44.854

10.992

10

4.0

2012/05/29

07:09:54

44.926

11.036

10.4

4.1

2012/05/29

08:25:51

44.901

10.943

3.2

4.5

2012/05/29

08:27:23

44.854

11.106

10

4.7

2012/05/29

08:40:58

44.892

10.962

5.3

4.2

2012/05/29

09:30:21

44.892

11.053

1.2

4.2

2012/05/29

10:55:57

44.888

11.008

6.8

5.3

2012/05/29

11:00:02

44.873

10.95

11

5.1

2012/05/29

11:07:05

44.876

11.076

15

4.0

th, 2012
Source: INGV

 

Further events  were recorded in the followings days (Table 4). It is worth reminding that another event was recorded on June 9th, with epicenter on the Venetian Prealps (Table 5).

TABLE 4

Date

Time (UTC)

Lat

Lon

Depth (km)

L

2012/05/31

14:58:21

44.88

10.867

5.8

4.0

2012/06/03

19:20:43

44.9

10.940

9.2

5.1

2012/06/06

04:08:31

44.434

12.354

25.6

4.5

2012/06/12

01:48:36

44.88

10.888

10.8

4.3

th, 2012
Source: INGV

 


TABLE 5

Date

Time (UTC)

Lat

Lon

Depth (km)

L

2012/06/09

02:04:56

46.209

12.444

7.1

4.5

th, 2012
Source: INGV

 

After the main event of May 20th, the number of displaced persons – initially 3000 – rose gradually. The victims were 7, 4 of which were workers: one in the collapse of a factory at Bondeno, two in the collapse of three industrial buildings at Sant'Agostino, and one in the collapse of an aluminum foundry.

The final estimation of damage, after the shock of May 29th, was much heavier. In total there were 26 victims, most of them workers, and 20,000 homeless.

Immediately after the first shock, ENEA gave the national Civil Protection Service its support to perform macroseismic observations and to assess the damage to houses and industrial buildings. Moreover, ENEA also provided the Emilia-Romagna’s General Directorate for the Promotion of Cultural Heritage with the assessment of the damage to churches and other historical buildings. The Civil Protection responded positively and assigned ENEA the task of performing safety controls on civil buildings, which was, of course, most urgent. Three teams of ENEA technicians began the on-site surveys in Cento, Bondeno, Finale Emilia on May 25th and, after the second shock of May 29th, in Novi di Modena, Carpi, Rovereto and Molinella. The activities, carried out on over 100 structures, were concluded at the beginning of July. In most cases, the activities were not limited to safety controls only: as a matter of fact, ENEA technicians participated actively in the design of the most urgent interventions to secure crumbling buildings. They also performed geological campaigns in the area affected by soil liquefaction. Finally, interventions on the cultural heritage started at the beginning of September and are still in progress; they include important structures like the very famous Ghirlandina Tower and the Cathedral in Modena.

The Pianura Padana Emiliana earthquake was characterized by the phenomenon of soil liquefaction and the heavy damage to cultural heritage structures (churches, castles, historical buildings) and to industrial buildings,  pointing out the importance of seismic preservation of such structures. All these issues are discussed in the papers of this Focus, in which the main results of the activities carried out immediately after the quakes are reported. The analysis of the data are still in progress and will be presented in the next future. We thank all the authors, ENEA's researchers and others, that contributed to realize this volume in a short time.

 

 

Per informazioni e contatti: infoEAI@enea.it


Paolo Clemente - ENEA, Technical Unit for Environmental Characterization, Prevention, and Recovery
Massimo Forni
- ENEA, Technical Unit for Seismic Engineering
Alessandro Martelli