Abstract
　Displacement records of strong motion seismographs(period=6 sec and magnification＝1) at 40 observatories of JMA duringt he 1983 Nihonkai-chubu earthquake (M=7.7) are investigated. The results obtained indicate the fact that seismic response of long-period structures during a great earthquake is considerably enhanced at large cities in Japan such as Yokohama and Niigata etc. Next, several important formulas are presented to calculate the partial derivatives of phase velocity, group velocity, medium response function, eigenfunctions, and amplitude spectra of Love wave with respect to medium and source parameters. At El Centro, the displacement ground motion generated by the 1968 Borrego Mountain earthquake can be synthesized. Calculations are carried out for disclosing effects of soil condition and source mechanism on wave-form of Love wave. The crustal structure has very significant effects on wave-form and duration, especially near-surface shear velocity is more significant than density. However, source parameters are not so sensitive to the amplitude compared with soil condition.

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