Extending Earthquakes' Reach Through Cascading
David Marsan* and
Olivier Lengliné
Earthquakes, whatever their size, can trigger other earthquakes. Mainshocks cause aftershocks to occur, which in turn activate their own local aftershock sequences, resulting in a cascade of triggering that extends the reach of the initial mainshock. A long-lasting difficulty is to determine which earthquakes are connected, either directly or indirectly. Here we show that this causal structure can be found probabilistically, with no a priori model nor parameterization. Large regional earthquakes are found to have a short direct influence in comparison to the overall aftershock sequence duration. Relative to these large mainshocks, small earthquakes collectively have a greater effect on triggering. Hence, cascade triggering is a key component in earthquake interactions.
Laboratoire de Géophysique Interne et Tectonophysique, CNRS, Université de Savoie, 73376 Le Bourget du Lac, France.
* To whom correspondence should be addressed. E-mail: david.marsan{at}univ-savoie.fr
