Long-period seismicity during magma movement at Volcán de Colima

Abstract

During the period from February to September 2005, Volcán de Colima produced 30 Vulcanian explosions of sufficient magnitude to produce pyroclastic flows of variable size, with a total volume of at least 2.5×10 6 m 3 . Swarms of long-period events were associated with each event, their duration ranging from about 6 h to 3 days and each swarm containing up to 886 events. The characteristics of the swarms have been studied to understand the source mechanism and their relationship with the Vulcanian explosions. In total, 12,548 long-period events were analysed using various comparative and statistical methods. Patterns were not apparent in the data with no correlation between different properties of the swarms (duration, magnitude or frequency of occurrence of LP events) and the magnitude of the associated Vulcanian explosion, whether recorded by seismicity, volume of pyroclastics or altitude of the eruption column. This, along with other characteristics of the swarms, such as the continuation of the swarm after the explosion, with an increase in longperiod event amplitude in some cases, suggests that the mechanism is not merely associated with the pressurization under an impermeable cap and resulting pressure differentials between adjacent volumes within the system. It is more likely that the production of long-period events is dominated by brittle fracturing on the margins of an ascending magma body. A model is proposed whereby the unloading above the ascending magma column produced by a Vulcanian explosion resulted in an increase in ascent rate, reflected in the increasing amplitude of long-period events. The results reflect the complexity of non-linear processes involved during magma ascent, degassing, crystallization and rupture of the impermeable plug during the Vulcanian process. At Volcán de Colima, as at many volcanoes, long-period events represent a useful precursor for eruptive activity. For monitoring, this paper highlights some useful analyses that can be carried out, which could illustrate certain characteristics of an eruptive episode. A preliminary model is presented of the conduit processes at work during the cyclic extrusive and explosive activity during 2005.

Multiparametric Approach in Investigating Volcano-Hydrothermal Systems: the Case Study of Vulcano (Aeolian Islands, Italy)

“…All these data suggest an ongoing unrest process. Indeed, a high rate of LP seismicity has often been associated with pre-eruptive behaviour at many volcanoes, including Redoubt, Alaska (CHOUET et al, 1994); Galeras, Colombia (GIL CRUZ and CHOUET, 1997); and Colima, Mexico (VARLEY et al, 2010). Similarly, eruptive activities at many volcanoes have sometimes been preceded by thermal anomalies within or near to craters, such as at Soufrière (St. Vincent) in 1971, where increases in lake temperature and evaporation rate took place (SHEPHERD and SIGURDSSON, 1978), and at Tokachidake, where the 1962 and 1988-1989 eruptions were preceded by increases of geothermal activity (OKADA et al, 1990).…”

Magmatic architecture of dome-building eruptions at Volcán de Colima, Mexico

“…Papale 1999); yet, volcanologists and modellers beg for a better description of the material involved during eruptions. Recent technological advances enable experimentation on synthetic Hess and Dingwell 1996;Holtz et al 1999;Caricchi et al 2007;Caricchi et al 2008a;Champallier et al 2008;Vetere et al 2010) and natural materials (Vigneresse and Tikoff 1999;Quane and Russell 2003;Spieler et al 2004a, b;Kennedy et al 2005;Kueppers 2005;Quane and Russell 2005;Sato 2005;Gardner et al 2006;Kueppers et al 2006a, b;Szramek et al 2006;Benson et al 2007Benson et al , 2008Smith et al 2007Smith et al , 2009Caricchi et al 2008b;Hess et al 2008;Koyaguchi et al 2008;Mueller et al 2008;Robert et al 2008;Tuffen et al 2008;Castro and Dingwell 2009;Cordonnier et al 2009;Del Gaudio et al 2009;Heap et al 2009;Ishibashi 2009;AlatorreIbargüengoitia et al 2010) under realistic P-T conditions, and such experimental contributions are significantly enhancing attempts to simulate volcanic eruptive phenomena (Mader et al 2004). Here, we assess the magmatic architecture of the dome-building eruptions at Volcán de Colima, in Mexico.…”

Distinguishing high surf from volcanic long‐period earthquakes

“…A sudden increase in either the number or amplitude of LP events is often a sign of volcanic unrest, and LP signals are frequently seen as swarms or groups of repeating events concentrated in time. Identification of LP swarms is important in volcano monitoring because they often precede significant eruptions [Pinatubo Volcano Observatory, 1991;Chouet et al, 1994;Neuberg et al, 2000;Varley et al, 2010].…”