Source constraints of Tungurahua volcano explosion events

Abstract

The most recent eruptive cycle of Tungurahua volcano began in May 2004, and reached its highest level of activity in July 2004. This activity cycle is the last one of a series of four cycles that followed the reawakening and major eruption of Tungurahua in 1999. Between June 30 and August 12, 2004, three temporary seismic and infrasonic stations were installed on the flanks of the volcano and recorded over 2,000 degassing events. The events are classified by waveform character and include: explosion events (the vast majority, spanning three orders of pressure amplitudes at 3.5 km from the vent, 0.1-180 Pa), jetting events, and sequences of repetitive infrasonic pulses, called chugging events. Travel-time analysis of seismic first arrivals and infrasonic waves indicates that explosions start with a seismic event at a shallow depth (<200 m), followed ∼1 s later by an out-flux of gas, ash and solid material through the vent. Cluster analysis of infrasonic signals from explosion events was used to isolate four groups of similar waveforms without apparent correlation to event size, location, or time. The clustering is thus associated with source mechanism and probably spatial distribution. Explosion clusters do not exhibit temporal dependence.

Rapid hazard assessment of volcanic ballistic projectiles using long-exposure photographs: insights from the 2010 eruptions at Tungurahua volcano, Ecuador

“…It is possible to observe a narrow mode that account for ∼30% of all trajectories and could correspond to a ∼20-m-diameter upper conduit. This estimation is coherent with the 10 m radius observed by Ruiz et al [2005] and slightly larger than the 3.7-6.7-m-radius calculated by Arellano et al [2008]. There is also a much wider and flatter mode that accounts for ∼60% of all trajectories and could correspond to a ∼70-m-diameter source area.…”

Stratovolcano growth by co‐eruptive intrusion: The 2008 eruption of Tungurahua Ecuador

“…[6] The current period of unrest began in Oct-Dec 1999 and consisted of intermittent mild strombolian eruptions [Ruiz et al, 2006]. Three eruptions on 14th July 2006, 16-17th August 2006 and 6-7th February 2008 produced widespread pyroclastic flows and ash falls, resulting in the loss of lives, repeated evacuation and damage to infrastructure [Global Volcanism Program, 2006].…”

“…Peaks in seismic and gas parameters preceded both 2006 eruptions and tiltmeter measurements have been interpreted as due to the formation of a bulge on the northern flank between 11-16th August Global Volcanism Program, 2006;Carn et al, 2008]. Ruiz et al [2006]: explosion events have shortduration pressure transients with an impulsive onset, while jetting tremors have emergent onsets with long-duration pressure codas. Of the 12,000 events of volcanic origin, most (59%) were identified as explosive due to the presence of infrasonic pulses arriving at the station a few seconds after the seismic signal.…”

Quantifying unsteadiness and dynamics of pulsatory volcanic activity

“…Data acquisition uncertainty considered as the absolute error. References: (1) Hill et al (1998), (2) INGV (2012), (3) Ripepe et al (2013), (4) Sahetapy-Engel et al (2008), (5) Iguchi (2013), (6) Druitt et al (2002), (7) Ruiz et al (2005), (8) Varley et al (2006), (9) Webb et al (2014), (10) Watt et al (2007), (11) Dirksen et al (2006), (12) Valade et al (2012), (13) Ripepe et al (2008 Unfortunately, this complexity is not encompassed by current classification schemes as they are mostly based on deposit properties, e.g. tephra dispersal, grainsize and/or erupted volume, with the assumption of steady-state conditions (e.g.…”