Tidal Triggering of Earthquakes

Analysis of the tidal stress tensor at the time of moderate to large earthquakes strongly suggests that shallow (< 30 km) larger magnitude obliqueslip and dip-slip earthquakes are triggered by tidal stresses. No corresponding triggering effect is seen for shallow strike-slip earthquakes or for any type of intermediate or deep focus earthquakes which have been studied. Tidal triggering is also discussed from the viewpoint of the ' dilatancy-diffusion ' model. Specifically, the model as usually stated, excludes the possibility of small earthquakes being tidally triggered.