High-resolution 3-D GPR applied in the diagnostic of the detachment and cracks in pre-Hispanic mural paintings at “Templo Rojo”, Cacaxtla, Tlaxcala, Mexico

Abstract

• Use of GPR in the detection of subsurface features in damaged mural paintings. • GPR allows estimating the state of adhesion of the mortar layers. • fractures or fissures can be identified by means of the polarity of the wavelets. • images in 3-D at different depths to identify size and geometry of detachment zones. Non-invasive methods are increasingly used in conservation projects which deal with cultural heritage. Among these, GPR has proved particularly effective to assess subsurface features in historic buildings, thus contributing to make the best decision in terms of efficiency when faced with restoration problems. The present survey deals with pre-Hispanic mural paintings from the so-called Red Temple in the archeological site of Cacaxtla-Xochitécatl (Mexico) which presented a very poor state of conservation, with apparent diffuse discoloration, losses and damages, fissures, cracks, and deformations. The aim of this paper is to verify whether GPR surveys allow estimating the state of adhesion of the mortar layers and identify the size and geometry of the detachment zones by means of 3-D analysis at different depths of the vertical surfaces investigated. Four surfaces of varying dimensions were selected from two murals. The results obtained are helpful to determine the degree of alteration of the support in order to plan its restoration in situ or, if need be, its removal and placement on a more stable support.