In the major ports in Japan the strong-motion eathquake and the erthquake response of structures have been observed for these ten years; and as of December 1970, about 580 accelerograms were accumulated. The observation network consists of 57 strong-motion accelerogra61phs.
　The present report is the sixth publication in the series, reporting accelerograms obtained in major ports in 1970. Reproduced accelerograms of the ground acceleration records exceeding 20gals are included. Digitized records, response spectra and Fourier spectra are provided on the records exceeding 50 gals. Response spectra are also given of earthquakes of May 16, 1968 in Aomori, May 18, 1940 in EI Centro and July 21, 1952 in Taft.