Seasonal Variation of Relaxation Time and Attenuation in Sediment at the Sea Bottom Interface

摘要

Monthly temperature profiles at a stationary location off Cochin (water depth of 76 meters) indicated fluctuations of sea bottom water temperature of the order of 11 °C in the annual cycle, with the maximum temperature occuring in March and the minimum in August. The influence of the variability of the temperature on the relaxation time and compressional wave attenuation in the sediment is investigated. The relaxation time-attenuation models of Lester R. LeBlanc et al. and Markus von Haumeder are used. An annual variation of 16^s in the relaxation time at 20 kHz and 46 /is at 2 kHz is observed. A variation of about 0.6 dB/m and 0.02 dB/m in the attenuation is seen at 20 kHz and 2 kHz respectively. It is shown that the relaxation time and attenuation are linearly dependent on the pore water temperature.