In-situ shear-wave sound speed and attenuation in sandy seabed sediment: frequency dependence from 500 Hz to 3 kHz

The acoustic behavior of seafloor sediments is a key topic in marine geoscience and engineering, and the shear-wave response provides essential information on sediment mechanical properties and wave propagation mechanisms. Furthermore, shear-wave properties have important practical applications in engineering geology, including the assessment of soil bearing capacity and the inversion of soil physical properties. Reliable in situ characterization of shear-wave sound speed and attenuation at low frequencies remains challenging. In this study, in situ shear-wave measurements were conducted in sandy tidal-flat sediments off Qingdao, China, using a self-developed differential-distance transducer system, over 500 Hz–3 kHz. The results show that shear-wave sound speed increases approximately linearly with frequency (positive dispersion), while the attenuation coefficient increases markedly with frequency. The measured data were compared with the Biot–Stoll (BS) model, the BS model including grain-contact squirt flow and shear drag (BICSQS model), and the modified, corrected, Revil, extended Biot (mCREB) model. The mCREB model provided the best in-sample fit, although its performance partly reflects parameter calibration. This study provides new in situ evidence for shear-wave frequency dependence in sandy sediments and supports the development of sediment acoustic models.