In this study, we analyzed the seismic radiation and deformation characteristics of the 2011 Van earthquake during aftershock events with the support of estimated dynamic parameters (seismic b‐value and radiation efficiency, ηR), 3D crustal cross sections of aftershock hypocenters, and deformation styles of Lake Van basin. The resulted variation in the b‐value exhibits two dramatic changes in the b‐value: one (b > 1) during the first 100 days of the mainshock and the other (b < 1) in the last 70 days of the mainshock. The constant b (b = 1) indicates a seismically active time interval and transitional variation in the b‐value from high to low. The estimated b‐value (b >1) reveals that the aftershock sequence comprised a large number of the small and same‐sized events of the Van mainshock due to the extreme material heterogeneity within the rupture zone. This indicates a general decrease in shear stress and increasing complexity in the focal area. The small value (ηR < < 1) of ηR implies that the amount of energy mechanically dissipated during the Van rupture process is large. This reveals that the microscopic breakdown process dominates the rupture dynamics and the whole Lake Van basin. The 3D crustal images of hypocenters suggest that the Van event originated in a strongly heterogeneous fractured setting with the aseismic sedimentary section of Lake Van. The high b‐value combined with the low radiation efficiency (ηR) shows a strongly faulted‐fractured sediment‐rock formation filled with gas‐fluid. This suggests that the seismic energy is intermittently released in the discrete form of aftershock events which is controlled by nonuniform and highly heterogeneous stresses, associated with the deformation style of Lake Van. The frequent redistribution of flickering stresses and nonlinear deformations in the rupture area increase the b‐value and decrease the radiation efficiency.
Part of the book: Earthquakes