Self-sustained oscillations at Volcán de Colima (México) 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 spectra mainly peaked in the range 0.3-2 Hz and characterized by a monotonic decreasing envelope, as those produced in a cylindrically-symmetric self-oscillating cavity interacting with a confined jet. Independent Component Analysis, a time-series 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 have a well defined spectral content and are self-sustained oscillations with low dimensionality, as shown by dynamic system reconstruction methods. Moreover, they show radial polarization in near field and transverse polarization in far field in North-West South-East direction. Finally, we hypothesize a branched plumbing system with two principal conduits having alignments orthogonal to one another

Monitoring methane emission of mud volcanoes by seismic tremor measurements: a pilot study

“…Seismic emissions relative to strombolian activity of hot volcanoes are characterized by remarkable complexity concerning both the spectral features of the intense background tremor and the waveforms of the typical energy bursts. This reflects complex dynamics processes occurring in the active structures, involving high energy gas-rock-magma coupling phenomena (Chouet, 1988;Julian, 1994;Fujita et al, 1995;Garcés et al, 1998;Konstantinuou and Schlindwein, 2003;Balmforth et al, 2005;Palo et al, 2009;Matoza et al, 2010;De Lauro et al, 2011), vibrations of magma-filled cavities, such as volcanic conduits, magma chambers or cracks (Crosson and Bame, 1985;Chouet, 2003;De Lauro et al, 2012), etc. None of these phenomena is expected to occur in mud volcanoes where low energy processes only take place (at least during the quiescent phase) as the effect of a slow gas seepage from depth through a mud-filled conduit.…”

Wavefield decomposition and phase space dynamics of the seismic noise at Volcàn de Colima, Mexico: evidence of a two-state source process

“…For each station, the panel on the left contains the distribution of RL fraction; the central panel displays the azimuth distribution; the right graphic shows the dip distribution. near field as well (Petrosino et al, 2011;De Lauro et al, 2012a). In addition, volcanic tremor with frequency content matching that of FB2 has been already observed in other areas (De Lauro et al, 2005;Haney, 2010) and a competition between volcanic and non-volcanic sources has been already detected at Stromboli, with the evidence of volcanic tremor during a phase of low-energy microseismic noise (De Lauro et al, 2005.…”

“…Consistently, decompositions in time-domain by high-order statistical methods of volcanic signals at high frequencies (> 0.5 Hz) have led to the extraction of few basic signals, modelled as the vibration modes of hydrothermal structures or magma-filled cavities (Acernese et al, 2004;De Lauro et al, 2009, 2012aDe Martino et al, 2011), whereas at low frequencies the superposition of volcanic tremor and microseismic noise has been detected (De Lauro et al, 2005Cabras et al, 2008).…”

“…Most vulcanian-style explosions are preceded by a high-energy transient seismic event with principal frequency peak at about 0.4 Hz and over-modes. This transient event is generated in the crater area and is induced by strong and rapid degassing flux interacting with the volcanic conduit and leading to the eruption (Zobin et al, 2006(Zobin et al, , 2010Petrosino et al, 2011;De Lauro et al, 2012a). Such pressurization (or long-period) events dominate the seismicity of active volcanic areas and share with the volcanic tremor very similar spectral content and wavefield properties, as the effect of a common source mechanism (e.g., Chouet, 1996;De Lauro et al, 2008).…”

“…Specifically, degassing permanently can put in vibration the main conduit of the plumbing system, exciting its fundamental vibration mode. During vulcanian-style explosions, the degassing flux is strongly enhanced due to the coherent rapid movement of aggregated magma-gas mixtures nucleated at a depth of 1-3 km, producing very energetic conduit oscillations with the appearance of higher vibration modes along the entire event and a broad spectrum just during the nucleation Petrosino et al, 2011;De Lauro et al, 2012a). Our scheme follows the behaviour of many volcanoes worldwide for which explosion-related seismic events and background signals are both manifestations of a common source, i.e.…”