Time-dependent Aftershock Seismicity Patterns and Their Propagation - The Van Earthquake (7.2), 23 Oct. 2011, E-Anatolia

Abstract

The Van earthquake (ML 7.2, 23 October 2011) occurred in E-Turkey, typically “intraplate” earthquake. Aftershock seismicity pattern of the Van earthquake indicates the most prominent type of compound-complex earthquakes due to its multifractal dynamic complexity and uneven compressional nature, ever seen all over Turkey. Aftershock seismicity of the Van earthquake can’t be explained with linearly uniform, elastic fracture mechanics, because the time delays between the observed individual clusters are too long to result from elastic processes. The Van earthquake dynamically loads the surrounding volcanic region, such a compound earthquake can result from viscoelastic relaxation in the immediate postseismic period, resulting in nonlinear and heterogeneous redistribution of loads. Van earthquake as a composite system has input parameters more than one and strongly characterized by composite sequences of event instabilities. This brings an idea that is intraplate seismicity of accretions, giving a possibility of the extensive investigation of post-collisional rheology of accretionary complexes. We conclude that, in Lake Van, the deep-reaching zones of weakness allow magmatic intrusions into upper crustal layers, where magma-fluids or unstable fluctuations of the magma chambers themselves may cause the generation of unstable evolution and propagation of earthquake sequences.