Explosive devices of the Second World War are found every week on French coasts (sometimes in dozens of meters of the bank) by divers, fishermen and by the mine warfare office of the ministry of Defense. These explosive charges range from some kilograms to some hundred kilograms. In a very short time after their discovery, they must be destroyed by the French Navy mine warfare Office. If the risks are well known by the mine warfare experts, the consequences of an explosion on the environment are much more complex to estimate and expertise of SHOM are then asked. During the last two years, SHOM realized 50 expert appraisals for 192 explosive devices discovered on the Mediterranean Coast. According to the geology, the explosive charges and their localization, the earthquake generated by the explosion can cause some nuisance for the watersides (e.g. vibrations in houses), even damages of infrastructures as done by natural earthquakes. At sea, they could activate, in such circumstances, submarine landslides: the energy produced by the explosion could be transformed into currents of turbidity and causing possibly breaks of submarine cables and\or local tsunami, in particular if the explosive device, of strong charge, is situated at the edge of the continental slope. Even if the probability of its case is low, this risk should not be underestimated, especially when continental shelf is narrow, as it is the case at the coasts of Provence and of Corsica. Thus POSA project focuses on Mediterranean coasts and proposes to address risk management, ahead of blasting operations in the marine field. The intended goal is to achieve a mapping of these risks for specific configurations and specifications and to develop a decision support tool for their control. For this, the relationship between: explosive charge - seabed and wave propagation, should be characterized and the environmental models and the seismo-acoustic simulation tools, adapted to the context. The originality of this project is based on the coupling of measurements during demining actions in the natural environment and associated modeling. So we will rely on geological measures at sea taken during clearance operations, explosive devices of the Second World War, of various powers, in various environments. Coupled with the analysis of sedimentary measurements, analysis of acoustic data measured on the seabed and coastal zone, with seismic data recorded on land by the seismic stations, will firstly established the characteristics of propagation in the different configurations, and on the other hand, calibration after a validation phase of the numerical simulations of wave propagation. This should enable the completion of a tool for quantifying risks from nuisances for habitants up to submarine landslides. Besides the aspect of defense-related risk management ahead of demining operations, the POSA project will also contribute greatly to civil research. Indeed, it will lead firstly to improve natural seismicity catalogs, allowing the distinction between man-against-related share of mining explosives and natural part of regional seismicity recorded. It will allow a better understanding of the propagation of seismic waves in the Earth's crust in the coastal zone, and thus a better location of natural seismicity, significant for the recognition of active tectonic faults and seismic hazard. POSA has a strong component modeling, interesting both civil and military aspects, which aims to move from observation to the forecast.