Assessment of Risks Induced by Countermining Unexploded Large-Charge Historical Ordnance in a Shallow Water Environment—Part II: Modeling of Seismo-Acoustic Wave Propagation

Abstract

The goal of this work presented in a two-companion paper is to pave the way for reliably assessing the risks of damage to buildings on the shore, induced by the detonation of large-charge historical ordnance (i.e., countermining) in variable shallow water environments. Here, we focus on the impact of the marine environment, more specifically the unconsolidated sedimentary layer, on detonation-induced seismo-acoustic wave propagation. We rely on a multidisciplinary cross-study including real data obtained within the framework of a countermining campaign, and numerical simulations of the seismo-acoustic propagation using a spectral-element method. We first develop a strategy relying on physical insights into the different kind of waves that can propagate in a coastal environment, to provide clues for a computational cost reduction. The geological surveys and the hydroacoustic measurements provide input data for the 3-D axisymmetric modeling of wave propagation. The numerical simulations, obtained for one specific source-receiver path with a variable sedimentary facies, are compared with the real seismic data induced by the detonation of a charge either on the seabed, or in the water column, and recorded on the coast. Numerical analysis sheds light on the strong interaction between surface waves and the sedimentary facies. The short-scale and deep Manuscript

Assessment of Risks Induced by Countermining Unexploded Large-Charge Historical Ordnance in a Shallow Water Environment—Part I: Real Case Study

“…These relationships enable to draw preliminary conclusions on the risk assessment with respect to inland infrastructures. Finally, the article ends with still open questions that are addressed subsequently in [3], thanks to the additional numerical modeling and analysis reported there.…”

“…The impact of the location of the source, namely on the seabed or in the water column, is also investigated. Some of these results will provide the input data for the numerical modeling developed in [3].…”

“…In other words, we have to understand how the seabed and the water layer influence the propagation of the seismo-acoustic waves that are generated by the UXO detonation and that reach the coast. In this article (Part I), we investigate this influence experimentally, whereas in Part II [3], we will rely on numerical simulations.…”

“…This feedback is very useful for future development of a decision support tool for the assessment of seismic risks, induced by underwater explosions, for inland infrastructures. Part II of the paper [3] describes the numerical modeling of the explosion-induced seismo-acoustic wave propagation in the Rade d'Hyères (France) and the results of the cross-validation between the numerical simulations and the real seismic data.…”

“…Part I, of interest here, is focused on the real case study of the risks induced by countermining unexploded large-charge ordnances in a very shallow water environment, namely the Rade d'Hyères (France), in the Mediterranean Sea. The goal of this article is twofold: 1) analyze the acoustic and seismic data recorded during the countermining of different large explosive charges (from 80-up to 680-kg TNT-equivalent weights), and draw preliminary conclusions regarding the risk assessment with respect to inland infrastructures; and 2) provide the input data (i.e., geologic and acoustic data) and the output data (i.e., seismic data) for the numerical modeling and the cross-validation tasks developed in [3].…”