2017 Ischia Earthquake: Macroscale Typological and Damage Assessment of Masonry Churches
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Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2019) 1482-1500 COMPDYN 2019 7th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.) Crete, Greece, 24–26 June 2019 2017 ISCHIA EARTHQUAKE: MACROSCALE TYPOLOGICAL AND DAMAGE ASSESSMENT OF MASONRY CHURCHES Claudia Casapulla1, Francesca Ceroni2, Antonio Formisano3, Piera Salzano2*, Andrea Prota4 1 Department of Structures for Engineering and Architecture, University of Napoli Federico II Via Forno vecchio, 36, 80134 - Napoli, Italy [email protected] 2 Engineering Department, University of Napoli ‘Parthenope’ Centro Direzionale is. C4, 80143, Napoli, Italy {francesca.ceroni, piera.salzano}@uniparthenope.it 3Department of Structures for Engineering and Architecture, University of Napoli Federico II Piazzale Tecchio, 80, 80125, Napoli, Italy [email protected] 4Department of Structures for Engineering and Architecture, University of Napoli Federico II Via Claudio, 21, 80125, Napoli, Italy [email protected] Abstract st On August 21 2017 an earthquake of magnitude Mw = 3.9 (Md = 4) occurred in Ischia Is- land (Napoli, Italy), causing numerous damages to ordinary and monumental buildings. In September 2017 teams from the University of Napoli Federico II carried out usability checks on churches. The damage evaluation of churches was performed by filling the II level survey form (A-DC). The surveys allowed constructing a significant database of 27 churches. A de- tailed analysis of the inspected churches was performed in order to identify: i) the percentage of usability; ii) the most recurrent structural typologies; iii) the most recurrent damages and failure mechanisms. Based on the collected information, statistical inquires were carried out for the inspected churches as a prodromal step for subsequent vulnerability analysis. Keywords: Churches, Seismic Vulnerability, Risk Mitigation, Cultural Heritage, Structural Damage. ISSN:2623-3347 © 2019 The Authors. Published by Eccomas Proceedia. Peer-review under responsibility of the organizing committee of COMPDYN 2019. doi: 10.7712/120119.7013.19536 1482 Claudia Casapulla, Francesca Ceroni, Antonio Formisano, Piera Salzano and Andrea Prota 1 INTRODUCTION st On August 21 2017, an earthquake of magnitude Md = 4.0 struck the Ischia Island with epicenter in Casamicciola Terme. This event caused two fatalities and many injured people. Despite the low magnitude, the earthquake produced significant damages to masonry and re- inforced concrete (RC) buildings. The event in fact showed many deficiencies of the building stock in Casamicciola Terme and Lacco Ameno municipalities[1][2]. Above all, the churches of the island have shown numerous damages. Past studies [3]-[12], indeed, highlighted that monumental buildings, in particular churches, are considerably vulnerable to dynamic actions due to their intrinsic vulnerabilities (open plan, greater height-to-width ratio, projecting parts, large openings, slender bell towers, absence of proper transversal connections). Ischia Island is located in the Gulf of Napoli, about 30 kilometres far from the city of Na- poli (Italy). It is a volcanic island with a surface area of 46.3 square kilometres. The island is very densely populated, with around 60,000 residents. There are six municipalities on the is- land: Ischia, Barano d’Ischia, Casamicciola Terme, Forio, Lacco Ameno, and Serrara Fontana. The island has always been historically characterized by a significant seismicity, especially in Casamicciola Terme area. The intrinsic seismicity is linked to the nature of the island. Is- chia is, indeed, a volcanic island that has been frequently characterized by low-magnitude earthquakes (located in the northern part of the island, mostly beneath the town of Casamicci- ola Terme at very shallow depths). In 1881 and 1883, Casamicciola Terme was hit by two of the most devastating earthquakes of the seismic history of the Ischia Island. Table 1 summarizes the main events that shocked the island since the XIII century, with the corresponding moment magnitude and maximum macro-seismic intensity recorded ac- cording to MCS scale [15]. Figure 1 shows a map of the epicentres of the historical seismic events that hit Ischia Island since the XIII century. Year Municipality Lat Lon Mw IMCS,max 1275 Ischia 40.743 13.942 4.01 VIII-IX Ischia Not 1557 40.721 13.953 3.5 Available Casamicciola 1762 40.746 13.909 3.5 VI-VII Terme Barano d’Ischia Not 1767 40.735 13.919 3.5 Available Casamicciola 1796 40.746 13.909 3.88 VIII Terme Casamicciola 1828 40.745 13.899 4.01 IX Terme Casamicciola 1841 40.749 13.899 3.25 VI Terme Casamicciola 1863 40.746 13.909 2.87 V Terme Casamicciola 1867 40.746 13.909 2.99 V-VI Terme Casamicciola 1881 40.747 13.895 4.14 IX Terme Casamicciola 1883 40.744 13.885 4.26 X Terme 1980 Serrara Fontana 40.718 13.89 4.37 V Table 1: Historical seismic events in Ischia (http://comunicazione.ingv.it/). 1483 Claudia Casapulla, Francesca Ceroni, Antonio Formisano, Piera Salzano and Andrea Prota 1841 1881 1863-1867-1762 1275 1883 1828 2017 1767 1557 1980 Figure 1: Historical seismic events in Ischia Island. 2 SEISMIC EVENT On August 21st, 2017 at 18:57:51 UTC (20:57:51 local), an earthquake of a duration mag- nitude Md = 4 struck the Ischia Island with the epicentre in Casamicciola Terme (40.74° lati- tude and 13.90° longitude). The earthquake produced significant damages, especially to churches and masonry buildings [1]. 2.1 Macro-seismic intensity surveys Immediately after the earthquake, macro-seismic surveys [16], [17] were performed by the emergency group QUEST (QUICK Earthquake Survey Team) of INGV, in collaboration with ENEA, aimed at assessing damages to buildings and estimating the macro-seismic intensities according to the European EMS scale [18]. According to the surveys, a “red zone” was outlined in the district of Casamicciola Terme, close to the epicentre. In this area, most of the buildings were made of masonry, with absence of reinforcing elements (i.e. tie rods). The most commonly used material was tuff, a soft vol- canic stone typical of Ischia subsoil and, more in general, of the whole Campania region. Moreover, an overall high vulnerability was found for old masonry buildings. This was at- tributable not only to the poor quality of masonry used, but also to significant structural changes performed in the buildings over the time. Figure 2 reports some examples of the damage observed on ordinary masonry buildings in the red zone of Casamicciola Terme [19]. Table 2 shows the list of investigated locations by the QUEST group and the assigned macro-seismic intensities according to the European EMS scale [18]. The macro-seismic characteristics of the 21st August 2017 earthquake show a concentra- tion of damages in the epicentre area with a very strong intensity attenuation, even at very small distances. This is a typical result of shallow earthquakes in volcanic areas (generally associated to low magnitude earthquakes). Furthermore, the localized distribution of damage within the red zone highlights a possible 1484 Claudia Casapulla, Francesca Ceroni, Antonio Formisano, Piera Salzano and Andrea Prota site effect in the hilly area of Casamicciola Terme, in agreement with what was observed after the 1883 destructive earthquake [16]. a) b) c) d) Figure 2: Damages recorded in the red zone of Casamicciola Terme (Ischia, Napoli) immediately after the Au- gust 21st 2017 event [19]: a) façade overturning in Via Ottringolo, Piazza Maio; b) partial collapse of a masonry building in Via Montecito, Piazza Maio; c) corner overturning in Via Montecito, Piazza Maio; d) shear cracks on masonry external walls in Via Montecito, Piazza Maio. Location IEMS Location IEMS Casamicciola Terme (red zone) VIII Forio IV-V Bagni VII Perrone IV-V Fango VII Piedimonte IV-V Marina di Casamicciola VI Buonopane IV Fontana V-VI Ischia IV Cretaio V Panza IV Lacco Ameno V Sant'Antuono IV Ciglio V Campagnano III-IV Fiaiano V Cuotto III-IV Monterone V San Domenico III Serrara V Sant’Angelo III Barano IV-V Succhivo III Table 2: EMS intensity for different areas of Ischia Island [16], [17]. 1485 Claudia Casapulla, Francesca Ceroni, Antonio Formisano, Piera Salzano and Andrea Prota 3 INSPECTIONS Immediately after the earthquake, several teams from University of Napoli Federico II car- ried out, under the coordination of the Ministry of Cultural Heritage (MiBACT), the usability checks on churches and monumental buildings, whose aim was to define provisional safety measures for the safeguard of buildings and their artistic content. A total of 27 surveys were performed on churches in the most affected areas of the island. The most damaged municipalities were: Casamicciola (6 inspected churches), Forio (17 in- spected churches) and Lacco Ameno (4 inspected churches). Figure 3 shows the map of the island with the epicentre of the earthquake and all the in- spected churches. In order to perform the inspections, the A-DC survey form [20] was adopted. The main aim of this form is to directly provide during the emergency phase usability checks for herit- age buildings hit by an earthquake. The application of this form is described in Section 4. 001 SMBC Santa Maria del Buon Consiglio 015 SFA San Francesco d'Assisi 002 SMP Santa Maria della Pietà 016 SMS Santa Maria del Soccorso 003 MSI Santuario Maria SS Immacolata 017 SMAP San Michele Arcangelo (del Purgatorio) 004 SAP Sant'Antonio di Padova 018 SSFP Santuario San Francesco di Paola 005 SPB San Pasquale Baylon 019 SV San Vito 006 SMMP Santa Maria Maddalena Penitente 020 CSSA Congrega SS Annunziata 007 SG San Gennaro 021 SRPM San Rocco Pio Monte S. Anna 008 SCB San Carlo Borromeo 022 SSA Santissima Annunziata 009 SLE San Leonardo 023 CDA Congrega dell'Assunta 010 SFS San Francesco Saverio 024 BSR Basilica Santa Restituta 011 SML Santa Maria di Loreto 025 SMA San Michele Arcangelo 012 SMLO Santa Maria di Loreto - Oratorio 026 SLU Santa Lucia 013 SS San Sebastiano 027 SD San Domenico 014 SGT San Gaetano Figure 3: Inspections performed in churches of Ischia Island after the August 21st 2017 event.