Spatial and temporal distributions of b-value in and around Shinmoe-dake, Kirishima volcano, Japan

Keita Chiba, Hiroshi Shimizu

Research output: Contribution to journalLetter

Abstract

Kirishima Shinmoe-dake, located in southern Kyushu, Japan, erupted in October 2017 after 6 years of quiescence. Analysis of volcanic gas indicates that magma upwelling from depth affected this eruption. Shinmoe-dake’s recent eruptive history also includes phreatic eruptions in 2008 and 2010 and a magmatic eruption in 2011. We examined spatial and temporal variations in b-values to investigate the magma plumbing system in and around Shinmoe-dake and its possible effects on unrest. A region with relatively high b-values (b = 1.5) is located at depths of − 1.0 to 2.0 km below sea level beneath the summit. It is likely that this anomalous region was generated by crustal heterogeneity, as it colocates to pressure sources. We investigated temporal variations in b-values from January 2007 to October 2017 in two regions: beneath the summit and 7.0–8.0 km northwest of the summit; the latter corresponds to the region above the locations of pressure sources related to the 2011 and 2017 eruptions. An increase in the b-value (b = 1.4) beneath the summit was observed beginning in early 2009, followed by a subsequent decrease (b = 0.9) immediately before and during the 2011 eruption. Similar temporal changes in the b-value were also observed beneath the summit before the 2017 eruption. From these results, we can infer that the increase and subsequent decrease in b-value express the activation of small cracks, due to the generation of hydrothermal fluids, and the development of cracks, which produces higher magnitude earthquakes, respectively. Meanwhile, a decrease in b-value (b = 0.6) was observed in the region northwest of the summit during the 2011 and 2017 eruptions. Thus, it is possible that the decreases in b-value in this region result from the activation of small cracks and the development of these crack systems and/or a change in the stress field near the magma chamber, which produce higher magnitude earthquakes.[Figure not available: see fulltext.].

Original languageEnglish
Article number122
Journalearth, planets and space
Volume70
Issue number1
DOIs
Publication statusPublished - Dec 1 2018

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temporal distribution
volcanoes
volcanic eruptions
Japan
spatial distribution
volcano
volcanic eruption
crack
cracks
magma
earthquake magnitude
temporal variation
earthquakes
activation
volcanic gas
upwelling water
sea level
hydrothermal fluid
magma chamber
stress field

All Science Journal Classification (ASJC) codes

  • Geology
  • Space and Planetary Science

Cite this

Spatial and temporal distributions of b-value in and around Shinmoe-dake, Kirishima volcano, Japan. / Chiba, Keita; Shimizu, Hiroshi.

In: earth, planets and space, Vol. 70, No. 1, 122, 01.12.2018.

Research output: Contribution to journalLetter

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abstract = "Kirishima Shinmoe-dake, located in southern Kyushu, Japan, erupted in October 2017 after 6 years of quiescence. Analysis of volcanic gas indicates that magma upwelling from depth affected this eruption. Shinmoe-dake’s recent eruptive history also includes phreatic eruptions in 2008 and 2010 and a magmatic eruption in 2011. We examined spatial and temporal variations in b-values to investigate the magma plumbing system in and around Shinmoe-dake and its possible effects on unrest. A region with relatively high b-values (b = 1.5) is located at depths of − 1.0 to 2.0 km below sea level beneath the summit. It is likely that this anomalous region was generated by crustal heterogeneity, as it colocates to pressure sources. We investigated temporal variations in b-values from January 2007 to October 2017 in two regions: beneath the summit and 7.0–8.0 km northwest of the summit; the latter corresponds to the region above the locations of pressure sources related to the 2011 and 2017 eruptions. An increase in the b-value (b = 1.4) beneath the summit was observed beginning in early 2009, followed by a subsequent decrease (b = 0.9) immediately before and during the 2011 eruption. Similar temporal changes in the b-value were also observed beneath the summit before the 2017 eruption. From these results, we can infer that the increase and subsequent decrease in b-value express the activation of small cracks, due to the generation of hydrothermal fluids, and the development of cracks, which produces higher magnitude earthquakes, respectively. Meanwhile, a decrease in b-value (b = 0.6) was observed in the region northwest of the summit during the 2011 and 2017 eruptions. Thus, it is possible that the decreases in b-value in this region result from the activation of small cracks and the development of these crack systems and/or a change in the stress field near the magma chamber, which produce higher magnitude earthquakes.[Figure not available: see fulltext.].",
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N2 - Kirishima Shinmoe-dake, located in southern Kyushu, Japan, erupted in October 2017 after 6 years of quiescence. Analysis of volcanic gas indicates that magma upwelling from depth affected this eruption. Shinmoe-dake’s recent eruptive history also includes phreatic eruptions in 2008 and 2010 and a magmatic eruption in 2011. We examined spatial and temporal variations in b-values to investigate the magma plumbing system in and around Shinmoe-dake and its possible effects on unrest. A region with relatively high b-values (b = 1.5) is located at depths of − 1.0 to 2.0 km below sea level beneath the summit. It is likely that this anomalous region was generated by crustal heterogeneity, as it colocates to pressure sources. We investigated temporal variations in b-values from January 2007 to October 2017 in two regions: beneath the summit and 7.0–8.0 km northwest of the summit; the latter corresponds to the region above the locations of pressure sources related to the 2011 and 2017 eruptions. An increase in the b-value (b = 1.4) beneath the summit was observed beginning in early 2009, followed by a subsequent decrease (b = 0.9) immediately before and during the 2011 eruption. Similar temporal changes in the b-value were also observed beneath the summit before the 2017 eruption. From these results, we can infer that the increase and subsequent decrease in b-value express the activation of small cracks, due to the generation of hydrothermal fluids, and the development of cracks, which produces higher magnitude earthquakes, respectively. Meanwhile, a decrease in b-value (b = 0.6) was observed in the region northwest of the summit during the 2011 and 2017 eruptions. Thus, it is possible that the decreases in b-value in this region result from the activation of small cracks and the development of these crack systems and/or a change in the stress field near the magma chamber, which produce higher magnitude earthquakes.[Figure not available: see fulltext.].

AB - Kirishima Shinmoe-dake, located in southern Kyushu, Japan, erupted in October 2017 after 6 years of quiescence. Analysis of volcanic gas indicates that magma upwelling from depth affected this eruption. Shinmoe-dake’s recent eruptive history also includes phreatic eruptions in 2008 and 2010 and a magmatic eruption in 2011. We examined spatial and temporal variations in b-values to investigate the magma plumbing system in and around Shinmoe-dake and its possible effects on unrest. A region with relatively high b-values (b = 1.5) is located at depths of − 1.0 to 2.0 km below sea level beneath the summit. It is likely that this anomalous region was generated by crustal heterogeneity, as it colocates to pressure sources. We investigated temporal variations in b-values from January 2007 to October 2017 in two regions: beneath the summit and 7.0–8.0 km northwest of the summit; the latter corresponds to the region above the locations of pressure sources related to the 2011 and 2017 eruptions. An increase in the b-value (b = 1.4) beneath the summit was observed beginning in early 2009, followed by a subsequent decrease (b = 0.9) immediately before and during the 2011 eruption. Similar temporal changes in the b-value were also observed beneath the summit before the 2017 eruption. From these results, we can infer that the increase and subsequent decrease in b-value express the activation of small cracks, due to the generation of hydrothermal fluids, and the development of cracks, which produces higher magnitude earthquakes, respectively. Meanwhile, a decrease in b-value (b = 0.6) was observed in the region northwest of the summit during the 2011 and 2017 eruptions. Thus, it is possible that the decreases in b-value in this region result from the activation of small cracks and the development of these crack systems and/or a change in the stress field near the magma chamber, which produce higher magnitude earthquakes.[Figure not available: see fulltext.].

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