A Case Study of Deformation Measurements of Istanbul Land Walls via Terrestrial Laser Scanning

Historical structures, buildings, bridges, and walls are very sensitive to deformations which can be caused by many factors, such as winds, heavy rains, extreme temperature variations, ground and soil settlements, tectonic loadings, and others. The mapping of 3-D deformation maps of building provides an opportunity not only to understand the structural changes, but also to detect zones with a potential risk of damage. The high spatial resolution of terrestrial laser scanning (TLS) technology allows monitoring historical buildings with millimeter accuracy. Two towers of Istanbul Land Walls were surveyed three times with the 5-month time interval. The accurate deviation maps were obtained from TLS's data by comparing epochs. Between first two campaigns, there happened an earthquake with the magnitude of Mw 5.7 with the epicenter of approximately 60 km from the study area. The findings and outputs of this article indicate that earthquake had a great impact on the monitored structures and deformations were found up to 15 mm for the tower I and up to 20 mm for the tower II.