Integrated Geophysical Survey Applied to the Mallorca Cathedral

摘要

In the development of the studies "diagnosis and expert works about structural behaviour of the Santa Maria Cathedral in Palma de Mallorca", several geophysical prospecting techniques have been applied. For column characterization, three seismic tomographies have been performed simultaneously with 40 GPR profiles, using the 1.5 GHZ antenna, in three columns for 3-D reconstruction. Also, one GPR profile, with a 900 MHz antenna, has been applied in each of the 14 columns. Finally, 19 GPR profiles have been carried out for walls and buttresses characteritzation. The main objectives of seismic tomography and GPR profiles applied to the columns has been to study the inner materials and identify zones of cracks and fractures. For seismic tomography, 120 ray traces in each column have been performed to assure high coverage. A high frequency waves have been generated by an instrumented hammer, and waves have been recorded by a piezoelectric accelerometer at more than 65000 counts per second (cps) to assure high quality arrival times. The tomographic algorithm used is the Simultaneous Iterative Reconstruction Technique (SIRT) with 2 centimeters pixels, less than p-waves resolution. Main objectives of GPR survey in walls and buttresses have been to study the material of the inner part of each constructive element and identify zones of cracks and fractures. Two profiles in six walls, two profiles in three buttresses and one profile in the extern wall crossing perpendicular buttresses have been carried out.