Conference on the great 1117 Veronese earthquake (Venice, 20th January 2017)

On Friday the 20th of January 2017, a conference hosted by the Istituto Veneto di Scienze, Lettere ed Arti at the Palazzo Franchetti in Venice commemorated the 900th anniversary of ‘the most severe north Italian earthquake’, as the 1117 ‘Veronese’ earthquake has been labeled. (http://www.istitutoveneto.it/flex/cm/pages/ServeBLOB.php/L/IT/IDPagina/1086; videos of the presentations are on line: https://www.youtube.com/watch?v=4LArtXCWyS8&list=PLfcFPNXyAOqYA9ie8eeoPU2ziSQFhHtQi)

The conference organisers – Carlo Doglioni, Emanuela Guidoboni and Gianluca Valensise – intended to discuss new discoveries relating to this seismic event and explore further research opportunities. The workshop had a strong multidisciplinary approach, including papers from historians, architects, archaeologists and seismologists. Since broad interest in the 1117 earthquake exists well beyond the Italian borders, I would like to briefly summarise the contents of this conference.

1117-mdp
The 1117 earthquake MDPs in northern Italy. Source: AHEAD, http://www.emidius.eu/ahead/main/

Carlo Doglioni (INGV, president, and University of Rome – La Sapienza) opened the proceedings by illustrating the geotectonic characteristics of northern Italy. He mostly focused on the seismic hazard caused by the compressive stress which distinguishes the eastern Alpine arc and the extensional mechanism of the earthquakes which is characteristic of the northern Apennines. Addressing the difficulty in locating the epicenter of the 1117 earthquake, he remarked that the fault responsible for this seismic event should be identified with one of those characteristic of the compressive regime of the eastern Alps.

Emanuela Guidoboni (EEDIS) presented research on the 1117 earthquake that she has coordinated since 1982. The last phase of her research was conducted between 2004 and 2005, when an impressive number of sources were combined together, leading to the identification of three distinct events: (i) the first occurred during the early morning of the 3rd December with an epicenter in southern Germany; the most severe event took place in the afternoon of the same day, with an epicenter located south of Verona; (iii) while a third, smaller event, possibly occurred in the same year but not on the same day, with an epicenter in northern Tuscany. Guidoboni also discussed the diverse sources of information used in order to refine the macroseismic evidence for the event, which included annals, chronicles, private documents, inscriptions, and architectural evidence.

Mauro Librenti (archaeologist from the University of Venice) focused on the latter source of information, presenting an updated overview of the architectural evidence from ecclesiastical buildings. Again, Librenti discussed what was done between 2004-2005, when a catalogue of buildings which existed in 1117 was created in order to research, in greater detail, the impact of this earthquake. The selection of buildings which were possibly damaged by the earthquake was therefore based on this survey. Librenti admitted that the identification of damaged buildings was at that time heavily dependent on old-fashioned studies of low reliability which, as a result, exaggerated the impact of the earthquake on the built environment. He gave the example of the recent work of Fabio Coden (University of Verona) who, through careful architectural analysis, dramatically reduced the number of affected sites which had previously been catalogued in Verona and its surrounding area. Stressing the need to adopt stratigraphical analysis of medieval buildings on a larger scale, he presented the noteworthy results obtained through such an approach at the abbey of Nonantola, where seismic damage and later repairs were identified, confirming the information provided by an inscription preserved above the doorway of the church of San Silvestro.

The paper by Eva Coisson and Carlo Balsi reported on a single case study – the Romanesque cathedral of Parma – Emilia Romagna. They first discussed the importance of approaching the study of historic buildings by characterising the seismic damage through comparison with damage caused by contemporary earthquakes. This is the case with the “Manuale per la compilazione della scheda per il rilievo del danno ai beni culturali, Chiese” (Handbook for the compilation of data for the survey of damage to cultural heritage: churches, developed and distributed by Protezione Civile) which provides many examples of the mechanisms of damage in ecclesiastical buildings. The speakers therefore presented seismic damage caused by the 1117 earthquake in the Cathedral of Parma, which, by the way, is attested by contemporary written sources. In particular, the collapse of the façade, as a result of the overturning of the tympanum, and the damage to the upper part of the nave walls were discussed. The paper also focused on the restorations works, which repaired the collapsed walls and introduced a new type of truss that reduced the building’s vulnerability to seismic loads. To my knowledge, this is one of the earliest examples of a physical mitigation solution adopted in a medieval European context.

Gianluca Valensise centred his paper on the tectonically-driven surface deformations in the Po Plain, showing how the seismicity of this area has influenced the hydrological network of the north Italian main rivers. Burrato also attempted to investigate the identification of the fault responsible for the 1117 earthquake. He first emphasised that the epicenter calculated based on the distribution of the known macroseismic data points lies in the lower plain of Verona, south of the north Italian city. Thereafter, alternative hypotheses for its location were discussed, notably those by Galadini et al (2001 and later 2005: north of Vicenza) and Galli (2005: Piadena, between Cremona and Mantua). A more recent study by Scardia et al 2014, regarded two inherited Mesozoic faults in the area of Nogara (south of Verona) and San Ambrogio (south-east of Verona) as the possible seismic source for the 1117 earthquake. This latter hypothesis was considered by Burrato as the most convincing one, as it matches with the macroseismic evidence suggesting that the most severe damaged area centred around and south of Verona.

Fabio Romanelli presented a paper about the seismic hazard in northern Italy, analysed through a physics-based model. Renata Codello and Alberto Lionello discussed the seismic risk threatening the cultural heritage in Veneto. They reflected on an alarming aspect: many restorations undertaken in the past with anti-seismic purposes paradoxically increased the seismic vulnerability of these structures. This is a result of the deliberate use of concrete which, in many cases, diminishes the building’s elasticity.

Francesco Doglioni (IUAV Venice) offered an overview on the seismic damage one can find in historic architecture, notably in medieval churches, and stressed the need to contextualize these features within the stratigraphic evolution of the analysed building. He presented fresh data from the monastery of San Vittore e Corona di Feltre (Belluno), where damage has been identified which may relate to the 1348 Carinthian earthquake. He also focused on the Arena of Verona, the Roman amphitheater which, according to some written records, was badly damaged by the 1117 event. Here, Doglioni evaluated some possible seismic damage, but he was very cautious in correlating this evidence with the 12th century north Italian earthquake. The conclusion of his paper was, therefore, that this monument requires further research.

Francesca Da Porto (University of Padua) presented a paper on the recent central Italian earthquake, centering her attention on the lack of seismic protection or basic mitigation solutions (such as iron chains, for instance), in the historic (mainly medieval) buildings affected by this seismic disaster. This is a frustrating aspect, given the seismic risk which characterises the central Apennines.

Stefano Grimaz (University of Udine) closed the conference with a contribution on the contemporary seismic risk in northern Italy and Friuli. He underlined that northern Italy, due to the population distribution and the presence of strategic economic activities is the area with the highest seismic risk in Italy. On the other hand, he remarked how seismic risk can change with time. In Friuli, the region which is currently least risky from a seismic point of view corresponds with the epicentral area of the 1976 earthquake. By virtue of the introduction of earthquake resistant buildings on a larger scale, the most seismically hazardous area of Friuli is now the least risky for earthquakes. Needless to say, we need to learn this lesson from Friuli!

The conference ended with a discussion which unfortunately I was unable to attend.

In conclusion, the conference was very interesting and well organized, as it brought together scholars from a variety of disciplines. A remarkable result of the conference is that, in some cases, the focus was not only limited to the identification of damage. Reactions to seismic destruction, too, was explored.  Another positive aspect is that it was able to attract media attention to one of the most destructive earthquakes in Europe in the last 1000 years, an element of fundamental importance to the perception of risk (Il Corriere della Sera, the most widely-read Italian newspaper, dedicated an article to the conference).

piazza-duomo-c-provincia-di-padova_ph-f-e-m-danesin
Piazza Duomo, Padua (click for source). Here, an up to 2.5m thick  layer of collapse associated with the 1117 earthquake is archaeologically documented (Brogiolo 2011).

At the same time, the conference also highlighted the fact that there is plenty of room for new research, as the information presented was almost the same as those published more than 10 years ago in Guidoboni and Comastri’s catalogue (2005). I am strongly convinced that further archival research and archaeological investigations might reveal new information. Archaeology, in particular, still seems to play a marginal role in the study of past seismic events. That was actually indirectly underlined by the surprising absence of any reference to the data presented by Paolo Galli (2005) concerning the Cathedral of Piacenza and – even more so – the extraordinary archaeological and architectural evidence from Padua published by Gian Pietro Brogiolo (2011), where a combined analysis of the medieval urban stratigraphy and standing buildings led to a new, impressively detailed overview of the effects of, and reactions to, the 1117 earthquake. From our side, Armedea has begun research on a number of medieval sites in Vicenza, which we hope will shed new light on this crucial seismic event. I hope this consideration will highlight the need to integrate archaeology (and archaeologists!) in the study of past seismicity in a more systematic and multidisciplinary way.

Some references cited in the text

Brogiolo G P (2011) Architetture religiose a Padova alla fine dell’XI secolo. In: Chavarria Arnau A (ed) Padova architetture medievali (progetto Armep 2007-2010). SAP, Mantua

Coden, F, (2010) “Terremotus maximus fuit”: il sisma del 1117 e l’architettura medioevale dell’area veronese. Arte veneta. Rivista di storia dell’arte, 67. pp. 7-24

Galadini F, Galli P, Molin D, Ciurletti G, 2001. Searching for the source of the 1117 earthquake in northern Italy: a multidisciplinary approach. In: Glade, T., Albini, P., Frances, F. (Eds.), The Use of Historical Data in Natural Hazard Assessments. Kluwer, Dordrecht, pp. 3-27.

Galli P (2005), I terremoti del gennaio 1117. Ipotesi di un epicentro nel Cremonese, Il Quaternario, Italian Journal of Quaternary Sciences, 18 (2), 87-100

Guidoboni E, Comastri A (2005) Catalogue of earthquakes and tsunamis in the Mediterranean area from the 11th century to the 15th century. Bologna

Guidoboni, E., Comastri, A., Boschi, E., 2005. The “exceptional” earthquake of 3 January 1117 in the Verona area (northern Italy): a critical time review and detection of two lost earthquakes (lower Germany and Tuscany). J. Geophys. Res. 110 (B12309), 20.

Scardia G, Festa A, Monegato G, et al (2015) Evidence for late Alpine tectonics in the Lake Garda area (northern Italy) and seismogenic implications. Bull Geol Soc Am 127:113–130. doi: 10.1130/B30990.1

Acknowledgements

I would like to thank Peter Brown and Christoph Gruetzner for revising the text.

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