RESONANCE PREDICTION OF DEEP SEDIMENT VALLEYS THROUGH AN EIGENVALUE METHOD

2-D resonance of different orders for a sediment valley embedded in a half-space is studied for anti-plane and plane-strain models. It is fo und that the resonant frequencies are properties of the valley while t he incident wavefield only affects the excitation of different modes. The dimensionless resonant frequencies are found to be independent of impedance contrast between the half-space and the valley. Based on thi s property, an eigenvalue method is proposed to determine resonant fre quencies of the valley. Resonant frequencies and mode shapes are obtai ned by solving an eigenvalue problem. The method is valid for valleys of arbitrary shape. The eigenvalue problem is solved numerically based on an indirect boundary integral method. The corresponding eigenfrequ encies are identified as the resonant frequencies of the valley for al l incident waves. The eigenvalue method results are verified by a spec tral-search method. The method is found to be numerically much more ef ficient than the spectral-search method.