Strong motion earthquakes exhibit high frequency components in acceleration records near epicentre. Recently, near epicentre motions have been recorded in Koyna valley, India and San Fernando valley, US A. There is a school of thought that some reservoirs of river valley projects cause earthquakes. If so, the structures in the river valleys would be subjected to earthquakes having high frequency components. This paper deals with elastic as well as inelastic spectral characteristics of three of the strong recent earthquakes in Koyna valley. For each earthquake, all the three components, namely, longitudinal, transverse and vertical are taken up for analysis. Thus, in all nine components are analysed. The inelastic behaviour considered is of elasto-plastic type. Seismic coefficients have been obtained considering elastic behaviour of structures and these can be used for design purposes. However, under strong ground motions, the structures could undergo deformations which extend in the post-elastic range. To cater for the inelastic action, a reduction factor technique has been used which can be used to obtain the seismic coefficients under inelastic conditions. Single degree of freedom systems have been considered which form the basic element for the analysis of more complex systems. The study indicates that special care has to be exercised in the design of short period structures located near epicentres of earthquakes.