Dynamical evolution of the community structure of complex earthquake network

¹ Department of Physical Engineering, Mie University - Mie 514-8507, Japan
² College of Science and Technology, Nihon University - Chiba 274-8501, Japan

^(a) suabe@sf6.so-net.ne.jp

Received: 29 February 2012
Accepted: 8 July 2012

Abstract

Earthquake network is known to be complex in the sense that it is scale free, small world, hierarchically organized and assortatively mixed. Here, the time evolution of earthquake network is analyzed around main shocks in the context of the community structure. It is found that the maximum of the modularity measure quantifying the existence of communities exhibits a peculiar behavior: its maximum value stays at a large value before a main shock, suddenly drops to a small value at the main shock, and then increases to relax to a large value again relatively slowly. Thus, a main shock absorbs and merges communities to create a larger community, showing how a main shock can be characterized in the complex-network representation of seismicity.