Exploring the evolution of a volcanic seismic swarm: the case of the 2000 Izu Islands swarm

摘要

The goal of this paper is to yield physical constrains onthe nature and evolution of a seismic swarm by means of aquantitative stochastic modeling of earthquakes occurrence.With this purpose, we fit different stationary andnonstationary stochastic ETAS models to the Izu Islandsseismic swarm occurred in 2000. We find that anonstationary model with background activity and p-valuevarying through time describes the observations better thanother simpler ETAS models. The coherent fluctuations ofthese parameters and of the spatio-temporal earthquakedistribution are interpreted in terms of a magma/fluidssource process that evolves through outbursts of activitysuperimposed to low frequency variations. The resultsobtained suggest that suitable nonstationary ETASmodeling can be very useful to characterize the nature ofthe swarm source, and it may provide the basis to build aquantitative tool for tracking in almost real-time theevolution of a magma/fluids source.