Seismic Microzonation: A Preventive Measure for the Conservation of the Built Heritage

Several earthquakes around the world verified the vulnerability of monumental buildings and the urgent action needed to protect them. This chapter assesses the necessity of performing detailed seismic studies in historical buildings (small-scale), due to the importance of this types of structures that deserve to be protected and conserved or, on the contrary, if the seismic microzonation in the city (large-scale) is enough. The case study is Murcia city and one of its most important historical buildings, the Cathedral of Santa Maria. The Murcia Region, located in southeast Spain, is classified as a seismically active zone. Multichannel Analysis of Surface Waves (MASW) method was used providing a characterisation of the materials in terms of shear-wave velocity (Vs), to obtain characterisation of the subsoil structure in historical buildings. The Vs investigations were carried out at the scale of a historic building and at the seismic microzonation scale in the city. Results evidenced a clear difference in Vs values obtained under the Cathedral and in the city. The study makes the case that the analysis of the local effect due to the shallow soil conditions in historic buildings, is a fundamental point to address the preventive analysis of the building seismic response, beyond studies of seismic microzonation carried out at city scale.