Seismic microzonation as a preventive measure for the conservation of historical heritage

Resumen

Several earthquakes have been taking place around the world, e.g. 2009 in L’Aquila (Italy), 2011 in Lorca (Spain), and 2017 in Axochiapan (Mexico). They verified the vulnerability of monumental buildings as well as the urgent action to protect them. Murcia Region is located in southeast Spain. This Region is classified as a seismically active zone with small to moderate magnitude earthquakes. Different seismic events recently occurred in the region: 1999 (Mula), 2002 (Bullas), 2005 (La Paca) and2011 (Lorca), with magnitudes (Mw) of 4.7, 5.0, 4.8 and 5.2 respectively and macroseismic intensity (I0) ranging from VI to VIII(EMS-98 scale). The Lorca earthquake generated catastrophic damages to historical buildings.Recent studies of seismic microzonation conducted in the southeast of Spain have highlighted the importance of soil conditions in the observed damage distribution. From the geological point of view, the city of Murcia is composed mainly of alluvial fans of different generations, constituted by sands and gravels, with silts and clays. The urban area of Murcia is located at Vega Media of the Segura River on the sediments of its ood plain (current river streambed). Owing to its features and the geographical situation,Murcia is a suitable zone to characterise the local site eect through the Vs30 values. This study is divided into two phases. Firstly, the metropolitan area of Murcia was characterised in terms of shallow Vs structure byusing Multichannel Analysis of Surface Waves (MASW). Five long proles were carried out following the different geological structures present in the study area. They have been performed by using the active and passive modes simultaneously. Secondly, the subsurface of the Tower of the Cathedral of Santa María will be characterised in the same terms. The Tower of the Cathedral of Santa María de Murcia belongs to the historical heritage of the Region, and is protected as a Cultural Interest Property in the country. The primary goal of this paper is comparing the Vs30 values obtained at large scale (metropolitan area) with the one obtained at small scale (under The Cathedral) by using MASW method. The comparison of results will reveal the inuence of the scale factor on the seismic microzonation studies to approach the preventive analysis of historical buildings, with application beyond the Murcia Region.