The scattering of seismic waves by a circular cavity with a partially debonded liner is studied by using the wave function expansion method and singular integral equation technique. The debonding region is modeled as an arc-shaped interface crack. For simplicity, the interaction between the crack edges is neglected. By expanding the wave fields in both liner and matrix as Fourier-Bessel series, the mixed boundary conditions lead to a set of simultaneous dual series equations, which may be further converted to Hilbert singular integral equations. Dynamic stress intensity factors describing the strength of dynamic interface traction at the ends of the bonding region and the scattering cross section are calculated by solving the singular integral equations numerically. The results show a distinguishing feature, the low frequency resonance, of such a problem.