Application of a moment tensor inversion code developed for mining-induced seismicity to fracture monitoring of civil engineering materials

• We present a novel application of a moment tensor inversion code (MTI_Toolbox).
• The MTI_Toolbox was designed for mining-induced seismicity for uniaxial measurements.
• We explore and explain the novel hybrid MTI option available in the MTI_Toolbox in detail.
• We propose to use the so-called condition number as a measure of accuracy for a result.
• We apply and evaluate the MTI_Toolbox to a concrete beam fracture experiment.

A moment tensor inversion (MTI) code originally developed to compute source mechanisms from mining-induced seismicity data is now being used in the laboratory in a civil engineering research environment. Quantitative seismology methods designed for geological environments are being tested with the aim of developing techniques to assess and monitor fracture processes in structural concrete members such as bridge girders. In this paper, we highlight aspects of the MTI_Toolbox programme that make it applicable to performing inversions on acoustic emission (AE) data recorded by networks of uniaxial sensors. The influence of the configuration of a seismic network on the conditioning of the least-squares system and subsequent moment tensor results for a real, 3-D network are compared to a hypothetical 2-D version of the same network. This comparative analysis is undertaken for different cases: for networks consisting entirely of triaxial or uniaxial sensors; for both P and S-waves, and for P-waves only. The aim is to guide the optimal design of sensor configurations where only uniaxial sensors can be installed. Finally, the findings of recent laboratory experiments where the MTI_Toolbox has been applied to a concrete beam test are presented and discussed.