Complex networks in astrophysical and geophysical systems
Jan 26, 2005
3:30PM to 4:30PM
Date(s) - 26/01/2005
3:30 pm - 4:30 pm
Title: Complex networks in astrophysical and geophysical systems
Speaker: Dr. Maya Paczuski
Institute: Imperial College, London, UK.
Location: ABB 102
Complex networks have attracted a great deal of attention recently as descriptions of biological, social, and technological systems. In this talk I demonstrate that they also arise in ordinary physical systems, and lead to new insights. Complex networks arise as (1) physical descriptions of astrophysical plasmas as well as (2) in capturing spatio-temporal correlations of earthquakes. Our recent analysis of observational data of the solar corona reveals that the flux tubes (links) and footpoints (nodes), where they attach on the photosphere, embody a scale free network. The statistics of solar flares and of the magnetic network structure are unified through a self-organized critical model where the avalanches and network co-generate each other into a complex, critical state. By invoking a metric to quantify correlations between earthquakes, networks of earthquakes are made by linking highly correlated events. This metric provides a simple and straightforward alternative to the usual method of analyzing earthquake correlations using space-time windows set by the observer. It also introduces the possibility of using recently developed ideas in complex network theory to reveal new correlation structures of seismicity. We find, for instance, that the earthquake network is both scale free and highly clustered. New scaling laws are found for the distances between earthquakes and their aftershocks. The original Omori law with $p=1$ emerges as a robust feature of seismicity, holding up to years even for aftershock sequences initiated by intermediate magnitude events.