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Masato Iguchi

Publications and source records attributed to Masato Iguchi.

3 recordsLinked to original sources
USGS2022

Discriminating types of volcanic electrical activity: Toward an eruption detection algorithm

We present a method for classification of the two distinct types of electrical activity that occur during an explosive volcanic eruption: vent discharges and lightning. Vent discharges occur at the onset of an explosion and create a distinctive radio frequency signature called continual radio frequency. Seconds to minutes after the onset of the eruption, lightning begins to occur throughout the eruption column. We use logistic regression to classify a radio frequency impulse as being part of either a lightning flash or a period of continual radio frequency. The classifier uses the number of peaks in the amplitude envelope from 1 ms windows before and after the impulsive very high frequency waveform, with an average accuracy of 97.9%. We propose that this method could be used in an algorithm to determine when explosive eruptions occurred by identification of the distinctive signatures of vent discharges and lightning.

Geophysical Research Letters↗
USGS2019

Overview of the eruptions of Sinabung Volcano, 2010 and 2013-present, and details of the 2013 phreatomagmatic phase

A small phreatic eruption of Sinabung Volcano, North Sumatra on August 28, 2010, at 18:30 local time marked the first eruption in the past ~1200 years. The eruption took place from two small vents in the south crater area. Explosions and ash emissions from these vents generated multiple ash plumes that reached altitudes of up to 5 km during early- to mid-September. By the end of September, only low level steam plumes were visible and the alert level was reduced from Level 4 (highest) to Level 3. The 2010 eruption effectively ended at this time. Beginning two days after the initial 2010 eruption, activity of the eruption has been monitoring continuously by a telemetered seismic network surrounding the volcano and by remotely sensed observations. This monitoring system was supplemented with a near-field continuous GPS network, beginning in February 2011. Persistent fumarolic emissions continued for almost 3 years following the 2010 eruption, before a new eruption began on 15 September 2013. This eruption continues to the present. The ongoing eruption is divided into 5 major phases: 1) phreatomagmatic phase (July 2013 - 18 December 2013); 2) first dome and collapse phase with pyroclastic density currents (PDCs; block-and-ash flows and related surges) to south (18 December 2013 - 10 January 2014); 3) lava-flow and collapse phase (10 January 2014 - mid-September 2014); 4) second lava dome and collapse phase with PDCs to south (mid-September 2014 - July 2015); 5) lava dome collapse and ash explosion phase with PDCs to southeast and east (August 2015 - present). The volcano erupted intermittently during the early phreatomagmatic phase with small vertical ash explosions. Then the eruption became increasingly vigorous with more repetitive and intense vertical ash explosions during late October through November. The first small pyroclastic density currents (PDCs) began on November 1. These pyroclastic flows descended the southeastern flank to a distance of 2 km.

Journal of Volcanology and Geothermal Research↗