Evaluation of Volcanic Activity at Sinabung Volcano, After More Than 400 Years of Quiet
Muhamad HendrastoSurono SuronoAgus BudiantoKristiantoHetty TriastutyNia HaeraniAhmad BasukiYasa SuparmanSofyan PrimulyanaOktory PrambadaAgoes LoeqmanNovianti IndrastutiAditya Sebastian AndreasUmar RosadiSucahyo AdiMasato IguchiTakahiro OhkuraSetsuya NakadaMitsuhiro Yoshimoto
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Before its 2010 eruption, Sinabung Volcano was a Btype volcano, in its Indonesian classification. A series of explosions featuring 1-5 km high phreatic-ash columns occurred from August 27, 2010 untill September 7, 2010. SO2 flux measured during the eruptions showed sizeable gas emission and the youngest volcanic product has age of 1200 years BP obtained from 14C dating. At the end of August 2010, four continuous seismic stations were established around the volcano, and 6 additional stations were deployed in October 2010. Deformation monitoring was conducted temporarily till in February 2011, four continuous GPS stations were installed. All were set up through collaboration between Indonesian and Japanese academic and government institutions. Hypocenter calculations using data of 4 seismic stations fromSeptember to October 2010 showed two concentrations for shallow volcanic earthquakes (VTB) 0.5-2 km beneath the crater and for deep volcanic earthquakes (VTA) 2.5-14 km beneath the crater. These epicenters defined a northeast-southwest lineament, near an elongated sinistral fault zone between Sinabung and Sibayak volcanoes. Earthquake sources went deeper northeastward. Results using the data of 10 stations from November 2010 to February 2011 showed that earthquakes were concentrated at depths of 4-6 km beneath Lake Lau Kawar. Tilt and Electro-optic Distance Measurement (EDM) measurements from August to September 2010 showed no significant changes We inferred that since the last explosion in 7 September 2010, stabilization process both in pressure and energy were low.Keywords:
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Abstract The Iwo-yama volcano of the Kirishima Volcanic Complex in Japan had a small phreatic eruption in April 2018, which newly formed multiple vents. The activity was recorded by two infrasound sensors and two monitoring cameras, which had been installed within 1 km of the vents. This study identified infrasonic signals from the multiple vents by a cross-correlation analysis between the two infrasound sensors. The analysis successfully revealed the signals from two main eruption craters and constrained the infrasound onsets at the individual vents in the two craters. We combined the infrasound results with the images from the cameras and reconstructed the sequence of the small phreatic eruption of Iwo-yama. At each of the two craters, the intense eruption, which was depicted by the evident infrasound signals, occurred several hours after the eruption onset. This study provides a sequence of the activities of the multiple vents in a phreatic eruption, which will be useful for understanding the phreatic eruption and hazard assessments.
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