Inverse analysis for determination of the complex shear modulus of bottom sediments from surface water wave-induced bottom motion

Abstract

An inverse procedure for complex shear modulus profile was developed based on the Yamamoto theory of poro-elastic bed response to surface water waves. Laboratory wave tank experiments were conducted to measure the wave-induced bed motion of sand beds and clay beds. Seismometers were used to measure the small motion of sand beds while movies were used to measure the large motion of clay beds. The complex shear modulus (rigidity and frame loss) profiles of beds were determined from the bed motion data using the inverse theory. Good agreements were observed between the inverted complex shear moduli and the complex shear moduli determined directly from the torsional resonance column tests. It is concluded that the proposed inverse method is powerful and useful for determining the bottom sediment properties in relation to geoacoustic modeling. [Work supported by ONR.]