Analysis of the seismic wavefield properties of volcanic explosions at Volcán de Colima, México: insights into the source mechanism

Abstract

S U M M A R YWe have investigated the wavefield properties of the seismic signals generated by the explosions of Volcán de Colima (México). We have analysed these properties to understand the initial mechanism that triggered the explosive events. Our study is focused on the direct waves coming from the crater area. Thus, we have analysed a set of moderate volcanic explosions at Volcán de Colima that was recorded by a small aperture seismic array over two periods: October 2005 and April 2006. We can distinguish two types of explosions, Vulcanian and ash-free events. Both types of explosions share the same characteristics, that is a long-period signal (not related to any type of emission) before the arrival of high frequency phases, and a later high frequency signal directly related to ash or gas emission. We have applied the Zero Lag Cross Correlation technique to obtain backazimuth and apparent slowness of the incoming waves. We have also applied polarization analysis to the record of every detected volcanic explosion. By comparing the results of both of these analyses, we have been able to identify the dominant wave types that comprise the seismic wavefield and infer in time and space a possible primary source mechanism that would trigger the volcanic explosions. We have observed an apparent slowness variation of the first onset of the long-period (LP) signal with a possible upward migration of the source; the depth of the source has been identified at a range between 2.6 and 3.3 km below the crater, associated with the range of measured apparent velocities relative to the first onset of the LP signal.

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.…”

Blowing Off Steam: Tuffisite Formation As a Regulator for Lava Dome Eruptions

“…Hence, it may be viewed that fragmentation increases degassing efficiency in silicic systems (Watts et al, 2002;Castro et al, 2014;Lavallée et al, 2015), and furthermore, relic fragmentation structures have been proposed as pathways that also allow passive bleeding of gases (Gonnermann and Manga, 2003;Castro et al, 2012;Burgisser and Degruyter, 2015) that may lower the explosive potential of an ongoing eruption. In addition, fragmentation has been linked to characteristic seismicity which occurs at shallow depth during magma migration (Neuberg, 2000;Green and Neuberg, 2006;Neuberg et al, 2006;SahetapyEngel et al, 2008;Palo et al, 2009;Varley et al, 2010;Arámbula-Mendoza et al, 2011;Thomas and Neuberg, 2012;Chouet and Matoza, 2013;Lamb et al, 2014;Webb et al, 2014;Arciniega−Ceballos et al, 2015). This seismicity can inform us of the timing of fragmentation events (e.g., Chouet, 1996), but when used in combination with field observations, can also provide information regarding subsurface processes and mechanisms that lead to fragmentation (e.g., Neuberg et al, 2006;Kendrick et al, 2014).…”

Self-sustained vibrations in volcanic areas extracted by Independent Component Analysis: a review and new results

“…9). This event has been associated with pressurization phenomena occurring within the volcanic plumbing system and has been labeled as a Long-Period (LP) event (Zobin et al, 2006;Palo et al, 2009;De Lauro et al, 2011).…”

“…10). Early works on LP events (recorded by short-period seismometers) indicated a predominance of frequencies in the range [1-2] Hz (Zobin et al, 2006;Palo et al, 2009). Recently, Fourier analysis of LP events recorded by broad-band instruments showed spectra with a decreasing envelope and sharp peaks, with the highest one at [0.4-0.5] Hz at all the stations (Fig.…”