Title: Seasonal modulation of seismicity: the competing/collaborative effect of the snow and ice load on the lithosphere,
Abstract: Seasonal patterns associated with stress modulation, as evidenced by
earthquake occurrence, have been detected in regions characterized by present
day mountain building and glacial retreat in the Northern Hemisphere. In the
Himalaya and the Alps, seismicity is peaking in spring and summer; opposite
behaviour is observed in the Apennines. This diametrical behaviour, confirmed
by recent strong earthquakes, well correlates with the dominant tectonic
regime: peak in spring and summer in shortening areas, peak in fall and winter
in extensional areas. The analysis of the seasonal effect is extended to
several shortening (e.g. Zagros and Caucasus) and extensional regions, and
counter-examples from regions where no seasonal modulation is expected (e.g.
Tropical Atlantic Ridge). This study generalizes to different seismotectonic
settings the early observations made about short-term (seasonal) and long-term
(secular) modulation of seismicity and confirms, with some statistical
significance, that snow and ice thaw may cause crustal deformations that
modulate the occurrence of major earthquakes.