Space/time coupling in brittle deformation at geophysical scales
Résumé
Strong intermittency as well as spatial heterogeneity characterize the brittle deformation of geophysical objects such as the Earth's crust or the Arctic sea-ice cover. They can be expressed through specific scaling laws, that relate, for a space-time domain, (a) the number of earthquakes or (b) the strain rate, vs. the size of the domain, for the Earth's crust or the Arctic sea ice, respectively. However, in both cases, spatial (respectively temporal) scaling depends on the time (respectively spatial) scale considered, i.e., the space and time scaling dependences are coupled. Here, we show that this space-time coupling of brittle deformation at geophysical scales can be summarized through a unique scaling law characterizing the discrete fracturing events (earthquakes or displacement events along sea-ice leads). As suggested by an analysis of southern Californian seismicity, we argue that this space-time coupling is likely to emerge from the complex correlation patterns related to chain triggering of earth- or ice-quakes.