Análise da propagação das ondas compressionais (P) em sedimentos marinhos e sua aplicação na caracterização das propriedades acústicas do ambiente

The physical properties of marine sediments have been systematically acquired and studied in various parts of the world. However, several theories have proved that sedimentological parameters such as grain size, bulk density, porosity and water content cause relevant dispersion in models of measuring wave propagation. The aim of this study is the investigation of the relationship between a relative broad spectrum of these physical properties and geoacustic parameters. Two different physical properties have been investigated: velocity and the attenuation of compressional waves. An apparatus was constructed to measure these physical properties using ultrasonic waves (2,25 MHz). Some experiments have demonstrated good results with this approach in terms of resolution and penetration rate. The first laboratory results were performed in cores collected on the continental shelf offshore the city of Arraial do Cabo, in Rio de Janeiro state. The preliminary experiments indicate that fine-grain sediments display distinguishable properties in terms of acoustic wave speed. More measures are being done in those cores. The propagation and dispersion will be also compared with extensive data sets taken from literature. The results obtained are encouraging and indicate a feasible method to analyze the relationships between compressional wave propagation and sedimentological parameters.