抄録
In the preceding paper, the characteristic frequency, power spectra, distribution of amplitudes and other characteristic features of waves in microtremors or short period microseisms at Hongo in Tokyo were discussed. In this paper, the results are described of the tripartite observations which were conducted at Hongo and Kokubunji in Tokyo, Kakioka in Ibaraki Prefecture and Matsushiro in Nagano Prefecture in order to investigate further in detail the character of propagation of microtremor waves.
The results obtained are:
1. Tripartite observations revealed phase velocities of 300m/s at Kakioka for vertical motion and 600m/s at Kokubunji for horizontal motion. The wave lengths 100m, and 250m were found respectively.
2. Short period microtremors with frequencies of more than 10c/s decrease notably during the night in amplitude.
3. Microtremors appear to be composed of waves which are generated from a number of surface sources and which have the character of surface waves.
