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International Journal of Geophysics
Volume 2012, Article ID 128465, 7 pages
http://dx.doi.org/10.1155/2012/128465
Research Article

Reverse Time Migration: A Seismic Imaging Technique Applied to Synthetic Ultrasonic Data

1Division 8.2 of Non-destructive Damage Assessment and Environmental Measurement Methods, BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany
2Geophysical Institute, KIT Karlsruhe Institute of Technology, Hertzstr. 16, 76187 Karlsruhe, Germany

Received 6 February 2012; Revised 24 May 2012; Accepted 25 May 2012

Academic Editor: Joerg Schleicher

Copyright © 2012 Sabine Müller et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Ultrasonic echo testing is a more and more frequently used technique in civil engineering to investigate concrete building elements, to measure thickness as well as to locate and characterise built-in components or inhomogeneities. Currently the Synthetic Aperture Focusing Technique (SAFT), which is closely related to Kirchhoff migration, is used in most cases for imaging. However, this method is known to have difficulties to image steeply dipping interfaces as well as lower boundaries of tubes, voids or similar objects. We have transferred a processing technique from geophysics, the Reverse Time Migration (RTM) method, to improve the imaging of complicated geometries. By using the information from wide angle reflections as well as from multiple events there are fewer limitations compared to SAFT. As a drawback the required computing power is significantly higher compared to the techniques currently used. Synthetic experiments have been performed on polyamide and concrete specimens to show the improvements compared to SAFT. We have been able to image vertical interfaces of step-like structures as well as the lower boundaries of circular objects. It has been shown that RTM is a step forward for ultrasonic testing in civil engineering.