Acoustic modeling for the characterization of polymetallic crusts from chirp type high-resolution seismic sources

The increasing knowledge of marine mineral resources, such as: recognition methods for remote location and exploitation is a strategic point. This fact can be justified by the growing demand for mineral resources and reserves and by the expected shortage of the land resources. In this context, this study aims to evaluate the acoustic behavior of artificially simulated signal for three distinct geological models indicating the more appropriate frequency spectrum (0.5 - 2.7 kHz, 0.4 - 4.0 kHz, 0.5 - 4.5 kHz e 1.0 - 6.0 kHz) for identification of marine polymetallic crusts. The attribute considered in the analysis was the maximum amplitude. To create the models, samples of polymetallic crusts collected in Vitoria-Trindade chain were used. The samples were profiled in the Multi-Sensor Core-Logger (MSCL) for determining Pwave velocity and density of gamma crusts. From the data analyzes it was concluded that: the application of acoustic methods with high resolution seismic source presents qualitative information that can be used in the localization of marine polymetallic crusts. The length of the echo showed lower values in the models where we had no crust and an increase with the crust thickness. This result may be related to the sum of the source characteristics of the interaction with the response to the way of propagation. Other relevants characteristics were the differences observed between the substrates. This may be related to the lower density and lower propagation velocity of the waves in sands and muds compared to basalts which showed an inverse trends as the crust becomes thicker. Regarding frequency, the moldel that presented the best result was 1.0 - 6.0 kHz, since the difference between the models with and without crust crust of 20 cm was more evident.