Self-sustained oscillations at Volcan de Colima (Mexico) inferred by Independent Component Analysis

Abstract

We have analyzed Long-Period (LP) seismic events of Volcan de Colima (Mexico) recorded by four three-component broad-band seismometers during January 2006. Frequency-domain analysis shows broad-band spectra mainly in the range 0.3-2 Hz characterized by a monotonic decreasing envelope, as those observed in a cylindrically-symmetric self-oscillating cavity interacting with a confined jet. Independent Component Analysis, a time decomposition method extracts two or three nonlinear oscillation modes depending on the station, with the fundamental one peaked at [0.4-0.5]Hz. These decomposed waves are self-sustained oscillations with low dimensionality and a well defined spectral content. Moreover, they show radial polarization in near field and transverse polarization in far field in North-West South-East direction. Finally, we depict a branched plumbing system with two principal conduits directed along orthogonal directions.