To acquire impulse response with sufficient accuracy where even when dynamic rigidity expressing a relation between the external force vibrating the objects and behavior of the objects in a frequency domain is characteristics with difference between values of real part in frequency corresponding to the upper and lower limits in the frequency domain for arithmetic operation object, the above relation can be represented in the time domain from dynamic rigidity.

Operation condition data for calculating dynamic rigidity of the ground representing a relation between earthquake motion and behavior of the ground by a frequency domain are acquired (100), dynamic rigidity of the ground is calculated (102) on the basis of the acquired operation data, the N complex data, S(ω1),---S(ωN), representing the values of dynamic rigidity at N kinds of frequency in the frequency domain for operation object are extracted (104) from the data of dynamic rigidity, respectively, the extracted complex data are substituted to formula (1) containing simultaneous components m(t0) of the impulse response depending on acceleration of the ground in addition to rigidity and damping terms and specifying the impulse response of the ground and also the simultaneous equations derived from formula specifying the dynamic rigidity of the ground determined on the basis of formula (1) concerned, and thus the impulse response of the ground can be operated (106), in which a relation between earthquake motion and behavior of the ground is represented in a time domain.