Scale experimental testing of the resolution capabilities of seismic tomography techniques

It is well known that tomographic seismic transmission techniques are being utilized more and more in applied geology and in non destructive tests owing to several advantages they offer over traditional surveys. The main tools described in this paper to carry out the scale experimental tests, were ultrasonic techniques. In order to perform the elaboration step, a software (DOGSTOMO) available on the market, utilizing the ART method (Algebraic Reconstruction Technique - regular grid) was considered. Also a tomography program based on the SIRT method to compare the results carried out by different processing approaches was utilized. Three different kinds of samples were chosen. In our opinion, their mechanical-physical characteristics make them representative of some natural systems. In more detail, samples were made up of different materials with a different homogeneity: plexiglas, concrete and brick. Furthermore, tests were performed in both non “perturbed“ conditions and with voids and artificial inclusions inside a brick structure. Experimental results show that discontinuities could be more or less highlighted by a tomographic technique, depending on which kind of material the sample is made up of. In spite of the good results obtained for homogeneous material (plexiglas) and for uniform porous material (concrete), the resolution carried out with both tomographic techniques applied to heterogeneous and fractured porous systems (brick), in which voids are localized in the regions where the sample is distinguished by a low propagation velocity, is very poor.