We consider an infinite space which contains one penny-shaped crack having the radius of a0 and the unit normal vector of . We compute the crack opening displacement when the crack is subject to a plane longitudinal wave of normal incidence from -x3 direction. The stress magnitude of the incident wave is p0. Also, Poisson's ratio is 0.25. This problem is solved with the conventional BIEM and FM-BIEM. Fig.3.52, Fig.3.54 and Fig.3.56 plot the total CPU time (sec) vs the number of unknowns when kTa0=1.4,3.2,4.4. In these figures lines marked ``Tdir'' and ``Tfmm'' indicate the CPU time required with the conventional BIEM and FM-BIEM, respectively. This figure shows that the FM-BIEM is faster than the conventional BIEM when the number of unknowns is larger than several thousands. Fig.3.53, Fig.3.55 and Fig.3.57 show the crack opening displacement where is the static opening displacement at the centre of the crack and . In these figures lines marked ``conv'' and ``fmm'' indicate the crack opening displacements obtained with the conventional BIEM and FM-BIEM, respectively. In Fig.3.58 ``numer'' indicates the crack opening displacement obtained with FM-BIEM numerically, and ``analytic'' stands for analytical solutions (Mal ). In Fig.3.59 the lines marked ``Elastostatics'' and ``Elastodynamics'' show the computational times required with FM-BIEM for elastostatics and elastodynamics ( kTa0=1.4), respectively. As in the case of Helmholtz's equation the computational time required by an elastodynamic analysis is longer than that required with an elastostatic one.