Evidence of Earthquake Triggering by the Solid Earth Tides
article i nfo Clearevidence forearthquake triggeringbythe earth tides hasremained elusive for morethan a century.Using the largest global earthquake catalog available (the NEIC catalog with 442412 events) we observe a clear correlation (with ~99% confidence) between the phase of the solid Earth tide and the timing of seismic events: earthquakes occur slightly more often at the time of ground uplift by the Earth tide, i.e. when normal stresses are reduced within the lithosphere. We observe that this phase distribution anomaly is larger for smaller and shallowerearthquakes.Although earthquakes inregionswithdominantlynormalandstrike slip faulting seem to exhibit more tidal triggering than regions dominated by thrust faulting, there is no statistically significant evidence for a focal mechanism dependence on earthquake triggering. Finally, we show here that it is highly probablethat the observedtriggeringiscaused bythe solid Earth tide, ratherthan byloading fromthe oceanor atmospheric tides. Although an additional impact due to loading from ocean tides is possible and probable, we cannot detect it here because the earthquake database is not sufficiently complete and homogeneous (more smallmagnitudeearthquakesinoceanicareasareneeded).Ourresultsareconsistentwiththeideaofadamped