ИСТИНА

For the analysis, the catalogs of earthquakes in Japan, Turkey, and the Azores were used. The spectra of the streams of such events are calculated. For weak earthquakes, the presence of a significant period of about 30 days was established. By the method of epochs, monthly daily numbers of earthquakes were constructed for the environment. The estimate of the possible influence of the lunar tide was checked using the Harvey formula. In the general case, the amplitudes of the monthly mean curves were comparable with those similar to those according to the Harvey formula. However, in some cases, the Harvey amplitude exceeded the amplitudes of the monthly mean curves. Thus, the observed effect can be interpreted as the influence of certain monthly industrial cycles on seismicity or noise at stations, as well as the influence of the lunar tide components with periods of about 30 days. The impossibility of distinguishing between industrial impact and tide is probably due to the width of the extremum of the period of about 30 days on the spectrum and insufficient resolution. IAGA-IASPEI 2021 | 490 However, the very existence of the spectrum extremum about 30 days is beyond doubt. Its identification is the more reliable, the weaker the earthquakes used for the calculations were. For Turkey, it turned out to be possible to show the great significance of the indicated spectrum peak for events from maritime territories