Discrete characteristics of the aftershock sequence of the 2011 Van earthquake

Abstract

An intraplate earthquake of magnitude Mw 7.2 occurred on a NE–SW trending blind oblique thrust fault in accretionary orogen, the Van region of Eastern Anatolia on October 23, 2011. The aftershock seismicity in the Van earthquake was not continuous but, rather, highly discrete. This shed light on the chaotic nonuniformity of the event distribution and played key roles in determining the seismic coupling between the rupturing process and seismogeneity.I analyzed the discrete statistical mechanics of the 2011 Van mainshock–aftershock sequence with an estimation of the non-dimensional tuning parameters consisting of; temporal clusters (C) and the random (RN) distribution of aftershocks, range of size scales (ROSS), strength change (εD), temperature (T), P-value of temporal decay, material parameter R-value, seismic coupling χ, and Q-value of aftershock distribution. I also investigated the frequency–size (FS), temporal (T) statistics and the sequential characteristics of aftershock dynamics using discrete approach and examined the discrete evolutionary periods of the Van earthquake Gutenberg–Richter (GR) distribution. My study revealed that the FS and T statistical properties of aftershock sequence represent the Gutenberg–Richter (GR) distribution, clustered (C) in time and random (RN) Poisson distribution, respectively.The overall statistical behavior of the aftershock sequence shows that the Van earthquake originated in a discrete structural framework with high seismic coupling under highly variable faulting conditions. My analyses relate this larger dip–slip event to a discrete seismogenesis with two main components of complex fracturing and branching framework of the ruptured fault and dynamic strengthening and hardening behavior of the earthquake. The results indicate two dynamic cases. The first is associated with aperiodic nature of aftershock distribution, indicating a time-independent Poissonian event. The second is associated with variable slip model, varying loading rates and high seismic coupling along the ruptured area. This study concludes that the aperiodic statistical behavior of the Van aftershock sequence is one of the results of the time-independent Poissonian seismic deformation in the 2011 Van earthquake.