Tides, earthquakes, and volcanoes

Kasahara, Junzo

'Large earthquakes and volcanic eruptions occur at subduction zones, major faults, volcanoes, and oceanic ridges. They are driven mainly by plate motion, but other factors can also trigger earthquakes and volcanism. For example, tides have long been implicated in their generation, although evidence has been sparse. A recent paper in Geology (1) makes the strongest case yet for tidal forcing of earthquakes and volcanism at mid-ocean ridges.' .... 'The above observations on submarine and terrestrial volcanoes show that earthquakes in volcanic regions near the shore and on mid-oceanic ridges display strong correlations with tidal forces. Fault movements that generate earthquakes may be accelerated by tidal stresses with directions suitable for creating shear movements. The direction of stress at the critical stage of fault failure and the presence of seawater penetrating into opening cracks at shallow crustal depth may explain why diurnal or semidiurnal changes in earthquake activity have been observed only for short periods during seismic events. By themselves the tidal forces are too small to generate earthquakes, but in the critical stage of faulting they can trigger volcanic earthquakes.'

Tides, earthquakes, and volcanoes

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