THE EFFECTS OF THE LORCA EARTHQUAKE ON HISTORICAL HERITAGE

Transcription

1 WCCE-ECCE-TCCE Joint Conference 2 Seismic Protec on of Cultural Heritage October 31-November 1, 2011, Antalya, Turkey THE EFFECTS OF THE LORCA EARTHQUAKE ON HISTORICAL HERITAGE Juan Jódar Mar nez *, Manuel Jódar Casanova * LORCA, MONUMENTAL CITY The town of Lorca, belongs to the Region of Murcia in Spain and is located southeast of the Iberian Peninsula, a geographical neighbor of the Be c Cordilleras, which form the edge of the Eurasian plate. * Civil Engineer, CETEC - Lorca. Engineering Consultants, Spain 141

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3 Juan Jódar Mar nez, Manuel Jódar Casanova It has a popula on of over 90,000 inhabitants, its privileged posi on as natural pass between Levante and Andalusia, has marked its history since numerous civiliza ons have se led in the Valley of Guadalen n, making Lorca its capital. These se lements have le many traces over the centuries, that has made Lorca in a monumental city of great, extent, and impressive cultural heritage. Its period of peak came in the Middle Ages when the Muslim Lurqa became the capital of Taif and one of the most important ci es of Al Andalus. With the Reconquista became a fron er of the Kingdom of Granada and was a key bas on of Chris anity un l The importance of the City throughout the history is viewed on the large number of historical monuments that it contains. The principal of them are the Castle, symbol of his fron er posi on in the late Middle Ages, and the Collegiate Church of St. Patrick, built between the sixteenth and eighteenth centuries. 143

4 The Effects of the Lorca Earthquake on Historical Heritage The town developed on the southeastern slope of the Sierra de Caño, a first walled military surrounding the summit, where stands the castle and a second wall with several medieval entrances to campus. 144

5 Juan Jódar Mar nez, Manuel Jódar Casanova From the sixteenth century, is forming a large urban center, declared a Historic- Ar s c Site in 1964, with buildings such as the Palace of Guevara, the Monumental de Santo Domingo, City Hall, the Casino or the Church of San Francisco. 145

6 The Effects of the Lorca Earthquake on Historical Heritage ALHAMA DE MURCIA FAULT The Guadalen n Valley, within the Region of Murcia, has a notable seismic ac vity, known throughout the centuries. 146

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8 The Effects of the Lorca Earthquake on Historical Heritage Many of the movements occurred associated with the called Alhama de Murcia Fault (AMF), which runs in the direc on of the Valley (NE-SO), over 85 km. From Huercal Overa (Almería) to Alcantarilla (Murcia). The fault runs through the town of Lorca, with a complex structure with two branches: the northern branch, dipping to the north and the south, south-dipping. This failure has been studied extensively by Bousquet (1979) and others, more recently, they consider their ac ve status and high sismicity poten al. According to the Preliminary Report of the IGME is a Thurst Reverse Fault. THE EARTHQUAKE OF 11 MAY 2011 On May 11, 2011, there were two major movements in Lorca, in a seismic series, whose characteris cs are given in the following tables; The two main movements occur very close to each other about on the trace of the northern branch of the Alhama Fault (AMF), according to the Preliminary Report of the Geological Survey of Spain (IGME) and the observa ons and data obtained by the Na onal Geographic Ins tute (IGN), which show, however, that most of the replicas are located southeast of the Fault. 148

9 Juan Jódar Mar nez, Manuel Jódar Casanova In any case the a ershocks are produced discon nuously in groups with a remarkable series on the night of 14 to 15 May, with more than 30 a ershocks. The accelera ons recorded in the IGN network sta ons are shown in the table below: The accelerometer of the Na onal Seismic Network, located in Lorca, recorded accelerograms that can be seen in the accompanying figures. 149

10 The Effects of the Lorca Earthquake on Historical Heritage As can be seen the maximum horizontal accelera on recorded during the main movement, cm/seg 2 was 369, well above forecasts of Earthquake Resistant Regula ons, which governs in Spain (NCSE-02). However, the short dura on of the shock (<2 sec), has prevented a more serious damage of the registered yet. The immediate consequences of the earthquake have been 9 deaths and 324 wounded, 49 of which require hospital treatment. In addi on, almost all of the 150

11 Juan Jódar Mar nez, Manuel Jódar Casanova people of Lorca, spent the night of 11 to 12 May, outside their homes, according to informa on provided by the Government Delega on in the Region of Murcia. As for the material damage is es mated that 80% of buildings have been damaged Lorca varying degrees, with an ini al damage assessment in total housing M., According to the Government Delega on in Murcia. All the damage as the Hon. Ayuntamiento de Lorca reach a higher figure of 1,000 M. 151

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13 Juan Jódar Mar nez, Manuel Jódar Casanova DAMAGE TO THE HERITAGE Importance of Damage The earthquake in Lorca (Murcia-Spain), has affected an area with huge historical heritage accumulated over the centuries and cultures, from the Neolithic, Bronze and Late Argar (Murviedro archaeological sites, Carraclaca, Cerro del Cas llo, etc.). un l today The town of Lorca, is a key geographical loca on in the domain of the route between the east and south of the Iberian Peninsula, established along the great valley of Segura - Guadalen n, we add the presence of water springs and the river, and the fer lity of the lands of the Valley. This has made important place of se lement of all cultures that have dominated this area of the Iberian Peninsula at all mes and, consequently, on its soil has accumulated enormous wealth in the form of archaeological sites, churches, convents, palaces and cultural values of all kinds. The ra o of Cultural Interest (BIC s), established by the Ministry of Culture of the Autonomous Community of Murcia, includes 75 historic buildings affected by the earthquake. Most of these buildings have been damaged in varying degrees. The preliminary report prepared by the IGME, contains a methodical analysis of the damage in a large number of buildings, made by geological structural analysis techniques, which can be seen in In general there have been collapses in the Historical Center buildings, but if largescale breaks for an earthquake of magnitude 5.1. However, the proximity of the hypocenter to the surface, the propaga on of rupture to the SW in the direc on of downtown, and prac cally, below this, together with the soil structure, formed by colluvial deposits of the streams tributary to Guadalen n which has amplified over the airwaves, have been the cause of a much higher damage than expected in an event the magnitude of which occurred on May 11, In essence, according to the report, the Lorca earthquake is an ideal example for the study of deforma on associated with near field during a seismic event and to correlate the damage with seismic intensity and parameters of the earthquake magnitude, depth and geometry of the seismogenic fault. Overall, the ini al assessment of damage to the historical heritage of Lorca, has been es mated by the Ministry of Culture, within the Recovery Plan for Cultural Heritage, 50 M. This plan will run for 5 years and will be financed by the Central Government, the Autonomous Community, Town Hall, Church and private equity, and is considered to require more resources. 153

14 The Effects of the Lorca Earthquake on Historical Heritage Types of Failures The effects produced by the earthquake in the historic buildings of Lorca all respond to certain types of failures common in similar situa ons. Thus, there have been falling cornices and decora ve elements, such as the Collegiate Church of San Patricio, Santuario Virgen de las Huertas and other buildings. 154

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17 Juan Jódar Mar nez, Manuel Jódar Casanova The breakage of the towers, steeples, and their rota ons were very illustra ve of the direc on of movement. Examples can be seen the towers of the churches of San Mateo, San Francisco, San ago, Santo Domingo, Santuario Virgen de Las Huertas, Convent of Las Clarisas. 157

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19 Juan Jódar Mar nez, Manuel Jódar Casanova 159

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21 Juan Jódar Mar nez, Manuel Jódar Casanova 161

22 The Effects of the Lorca Earthquake on Historical Heritage There have been falls of walls and disloca on with drop of covers by loosing their support, as in the churches of Carmen, San ago and Convent of Las Clarisas. 162

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24 The Effects of the Lorca Earthquake on Historical Heritage The domes of Santo Domingo, San Francisco, San ago, and other churches have either suffered the disloca on of his supporters, or total loss of these, with falling of the covers. 164

25 Juan Jódar Mar nez, Manuel Jódar Casanova CONCLUSIONS The main movement of the recent Lorca seismic series, was registered on May 11, 2011, at 16:47 GMT, and had, according to data provided by IGN, a magnitude of 5.1. It was preceded by another of magnitude 4.5, recorded at the 15:05 GMT, followed by an a ershock, among others, of magnitude 3.9 at 20:37 GMT. The first two movements caused horizontal accelera ons with very important peaks (PCA), of 270.7cm/seg 2 and 360 cm/seg 2, respec vely in the NS component and of and cm/seg 2 cm/seg 2 in EW component, much higher than could be expected in the Lorca area, according to Spanish Building Earthquake Regula ons (NCSE-02). The ver cal component was cm/seg 2 in the main movement. The maximum intensi es were, according to IGN records, VI and VII in the EMS scale. The distance from the epicenters to the town of Lorca, 3.5 and 2.9 km., respec vely, and depth between 2 and 3 km. These characteris cs, together with propaga on of the earthquake towards the SW where is the city center, and the geomorphological condi ons of the ground may be the cause that the severity of the damage was much higher than would be expected from a movement of magnitude 5.1. Lorca has a very important very important concentra on of monuments, with a wide range of buildings and assets cataloged as BIC (Interes ng Cultural Assets). This has meant that the damage to the Heritage has been great and varied in their type. This wide variety of damage and how they have produced will enable major advances in the understanding of the effects of earthquakes on the Historical, the behavior of buildings and methods of reconstruc on or rehabilita on. 165

26 The Effects of the Lorca Earthquake on Historical Heritage In this sense, Lorca Earthquake has le a mark and a stage that must be visited by researchers of this knowledge area. Early es mata ons for the reconstruc on of about 75 BIC s are over 50 M (June 2011), although this es ma ons may be much higher as the analysis would be deeper into the knowledge of structural damage. The reconstruc on of the historical heritage of Lorca requires a financial investment, administra ve and poli cal, so big it will take years or a decade of work. The reac on of some public and private, in the first moments a er the catastrophe has been exemplary, and as hope in the future, the three following pictures, taken just days a er May 11. The Lorca people hope that this great solidarity from the very beginning, stay un l the city can look back the rich heritage accumulated along its intense history. Reference Lorca earthquake 11/05/2011.Ins tuto NE Series Na onal Geographic. Ministry of Development. Preliminary Geological Survey Earthquake Lorca&#39;s May 11, 2011, 5.1 Mw IGME, Ac ve Tectonics Group, Paleoseismicity and associated risk of UCM, UAM and URJC. Seismic Sequence Lorca. So a López González. Day of Earthquake Engineering. Earthquake in Lorca. Colegio de Ingenieros de Caminos, Canales y Puertos. 11crm@ciccp.es Digital Murcia. D. Photos Michael S. Puchol and Diario La Verdad 166