Abstract
　An analytical methodology for predicting seismic ground strain is proposed by empIoying fault dislocation theory and surface-wave excitation theory, which wi1l be used for the mitigation of seismic damages of buried lifelines. Through discussions on influence of subsurface elastic parameters on phase volocity using the inverse surface-wave problem, it is found that shear-wave velocity is particularly an important parameter for ground strain estimation. With application of modal superposition, it is shown that the effect of higher modes becomes significantly non-negligible for simulating relative ground motions in the frequency range of engineering interest. Surface waves are calculated with given fault parameters of the l971 San Fernando earthquake. They are compared with the longitudinally and transversely polarized ground motions observed at Vanowen Street, California. The synthetic normal strain provides good agreement with the inferred results. Moreover, the relationship between relative ground motions and separation distance is quantitatively discussed.

*京都大学工学部
Faculty of Engineering, Kyoto University