Abstract

Positions of earthquakes over 5 th magnitude were investigate in Taiwan region and adjacent Philippine Sea Plate. Purpose of this paper was to establish earthquakes tidal periods in range of Moon sidereal rotation cycle. Because sidereal Moon cycle reflects variation in length of day of Earth, positions of earthquakes on this graph stated positions on Moon's orbit and from it followed the tidal frequences knowing time. 849 earthquakes after declusterization were investigated in three time periods 1962-1982, 1983-2002 and 2003-2024. Histograms of earthquakes compiled for Moon crossing equator from south, reaching maximum Moon declination, reaching Moon equator from north and reaching maximum negative declination, presented tidal frequence 6.83 days, 13.66 days and their multiples. By this way stated earthquake occurrence periods are only 31.8 %, but remaining earthquakes have also tidal origin given tectonic position on Taiwan and cumulative action of northsouth and westward directing forces.