Study Of The Correlation Between The Earthquakes And Tidal Stresses

In this paper,we selected Japan and its sea area,Indonesia,Southern California and Taiwan and its sea area as the study areas,using the earthquake catalogue from January 1990 to May 2018,and divided respectively these regions into some sub-regions.Firstly,we calculated the distribution of p-values by using Schuster’s test.The p-value represents the significance level of the null hypothesis that rejects the tidal phase angles randomly distributed in time and p<5%indicates that there was a correlation partly between earthquakes and tidal triggers in the region.We picked some sub-regions with p<5%to calculate tidal Coulomb failure stress values of earthquakes with M≥4.0 in these sub-regions,and we combied p-values with tidal Coulomb failure stress for analyzing the correlation between seismic activity and tidal stress in these sub-regions.On this basis,Schuster spectrum was built to further analyze the sub-regions were mentioned above,to study the tidal modulation of which periodic components were mainly affected by seismic activity in these regions.We drew the following conclusions:1.Japan and its sea area was divided into 81 sub-regions,and there were 22 sub-regions with p<5%by using Schuster’s test.We selected therein four sub-regions,and calculated values of tidal Coulomb failure stress were positive,which showed seismicity were affected by a certain degree of tidal triggering.The Schuster spectrums were established and showed seismicity of the four sub-regions were mainly modulated by semi-diurnal tides(T = 0.5),others were affected by other factors(T = 1.6～2.0).These results indicated there was a possibility that tidal stress affect seismicity in Japan and its sea area,and were mainly modulated by semi-diurnal tides.2.Indonesia was divided into 255 sub-regions,and there were 27 sub-regions with p<5%by using Schuster’s test.We selected therein two sub-regions,and calculated values of tidal Coulomb failure stress were positive,which showed seismicity were affected by a certain degree of tidal triggering.The Schuster spectrums were established and showed seismicity of the two sub-regions were mainly modulated by diurnal tides(T = 1.0),others were affected by other factors(T = 1.2～2.0).These results indicated there was a possibility that tidal stress affect seismicity in Indonesia,and were mainly modulated by diurnal tides.3.Southern California was divided into 33 sub-regions,and there were 10 sub-regions with p<5%by using Schuster’s test.We selected therein two sub-regions,and calculated values of tidal Coulomb failure stress were positive,which showed seismicity were affected by a certain degree of tidal triggering.The Schuster spectrums were established and showed seismicity of the two sub-regions were mainly modulated by diurnal tides(T = 1.0),others were affected by other factors(T = 0.1～0.40 and T=1.2～2.0).These results indicated there was a possibility that tidal stress affect seismicity in Southern California,and were mainly modulated by diurnal tides.4.Taiwan and its sea area was divided into 18 sub-regions,and there were 3 sub-regions with p<5%by using Schuster’s test.We selected therein two sub-regions,and calculated values of tidal Coulomb failure stress were positive,which showed seismicity were affected by a certain degree of tidal triggering.The Schuster spectrums were established and showed we weren’t find modulation of short-period tides or any other periods.These results indicated there was a possibility that tidal stress affect seismicity in Taiwan and its sea area,but weren’t modulated by short-period tides.