Extending Earthquakes' Reach Through Cascading

Abstract

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.

A new estimation of the decay of aftershock density with distance to the mainshock

“…This thorough description of the algorithm develops on the initial results discussed in the study of Marsan and Lengliné [2008].…”

“…[3] In order to avoid these shortcomings, we have developed a different method for isolating mainshockaftershock pairs, building on Marsan and Lengliné [2008]. With this method, like previous ones also based on stochastic modeling [Kagan and Knopoff, 1976;Zhuang et al, 2002Zhuang et al, , 2004, the relationship between any two earthquakes A and B is measured by the estimated probability w AB that B is an aftershock of A.…”

Multidimensional earthquake frequency distributions consistent with Non-Extensive statistical physics: The interdependence of magnitude, interevent time and interevent distance in North California

“…It is worth noting, however, that the moderate -good temporal correlation of the mixed process persists at M c  4 Although these results cannot be light-heartedly extrapolated to larger magnitude scales, the observation may suggest that at intermediate magnitude scales, aftershocks and background events are entangled and interact, thus producing SOC phenomenology in the temporal expression of regional seismicity. According to this view, aftershocks may be an integral part of the regional seismicity process and not just localized peculiarities (also see Marsan and Lengliné, 2008). The analysis of the raw NCEDC catalogue (Figure 5a) shows that q M is consistently determined as a function of interevent distance.…”

“…A formal explanation of such an effect is pending, but may nevertheless involve delayed remote triggering of seismic activity by (transient or static) stress transfer from the main shocks and large aftershocks and/or cascading effects already discussed by Marsan and Lengliné (2008). In this view, the effect weakens when aftershocks are removed because aftershocks are the link between the main shocks and their remote offshoot.…”

Drilling Into Faults Quickly After Earthquakes

“…Current data suggest that up to 80% of all earthquakes are triggered by another earthquake, and therefore earthquake triggering provides a general window into earthquake initiation [Marsan and Lengliné, 2008]. A quickly drilled borehole can record the stresses and interactions of aftershocks.…”