|Title||No clear evidence for localized tidal periodicities in earthquakes in the central Japan region|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Wang W., Shearer PM|
|Journal||Journal of Geophysical Research-Solid Earth|
|Type of Article||Article|
|Keywords||phase bin declustering method; stress; tidal triggering of earthquake; tides; tohoku-oki earthquake|
We search for possible localized tidal triggering in earthquake occurrence near Japan by testing for tidal periodicities in seismicity within a variety of space/time bins. We examine 74,610 earthquakes of M3 in the Japan Meteorological Agency catalog from January 2000 to April 2013. Because we use many earthquakes for which accurate focal mechanisms are not available, we do not compute tidal stresses on individual fault planes but instead assume that the mechanisms are likely to be similar enough among nearby events that tidal triggering will promote earthquake occurrence at specific tidal phases. After dividing the data into cells at a range of spatial (0.2 degrees, 0.5 degrees, and 1.0 degrees) and temporal dimensions (100, 200, and 400days), we apply Schuster's test for nonrandom event occurrence with respect to both the semidiurnal and semimonthly tidal phases. Because the resulting p values will be biased by temporal clustering caused by aftershocks, we apply a declustering method that retains only one event per tidal cycle per phase increment. Our results show a wide range of p values for the localized earthquake bins, but the number of bins with very small p values (e.g., p < 0.05) is no more than might be expected due to random chance, and there is no correlation of low p value bins with the time of the 2010 M 9.0 Tohoku-Oki earthquake.