2012/5/18

Volcanic activity of Sakurajima volcano, South Kyushu, Japan

Masato Iguchi Sakurajima Volcano Research Center, DPRI, Kyoto Univ. 132E Volcanoes in Kyushu Aso 130E

110 volcanoes in Japan Unzen

Kirishima Volcano Complex 32N

Sakurajima

Russia Kaimondake

Satsuma-Iwojima Japan Sea

Korea Kuchinoerabujima

Japan 30N Pacific Ocean Nakanoshima

Suwanosejima 2011 Eruption at Shin-moedake of Kirishima Volcano Complex

Sub-plinian eruption on January 26, 2011 Lava dome

Mr. Shimousuki, Kagoshima International Aviation Deflation due to sub-plinian eruption on January 26, 2011 Slope distance change

inflation Quick turn to inflation Historical eruption of Sakurajima AD 0 Submarine eruption in 1780 1779 Kitadake 500

1471-76 764

1914 1000 1946

764 1471- 1500 1476 1471-76 1779 1914 Minamidake 1779 1914 Showa crater 2000 Historical eruptions

Bunmei An’ei Taisho Showa eruption eruption eruption eruption 1471-76 1779-80 1914 1946 Vent location NE-SW N-S E-W E Volume of 0.5 1.7 1.34 0.18 lava (km3) Volume of 0.7 0.4 0.52 0.02 tephra (km3) Plume height unknown 12,000m 8,000m 2,000m Casualties many 163 58 1 VEI 5

Eruption in 1779 Eruption in 1914 Eruptive activity of Sakurajima

Minamidake crater Showa crater

1000 南岳爆発回数 年間爆発回数 昭和火口爆発回数 Annual number of explosion 800 2012年 3月まで 600

400

200

0 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 3000 30 火山灰量（万トン）Annual weight of volcanic ash (million ton)

200020

100010

No measurement1977年以前は測定なし before 1977 0 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Increase in eruptive activity Lava dome in crater The first explosion on February300 3, 2008

250

200

150 JMA

100 空気振動振幅 (Pa) 空気振動振幅 50 Explosion at Minamidake Increase in October 3, 2009 0 eruptivity 1/1 4/1 7/1 10/1 1/1 4/1 7/1 10/1 1/1 4/1 7/1 10/1 1/1 4/1 7/1 10/1 1/1 4/1 200 3500 積算回数 Increase in 180 eruptivity 3000 160 140 April 9, 2009 2500 120 Pyroclastic flow 2000 100

80 1500 積算回数 月別爆発回数 60 1000 40 500 20

0 0 number Cumulative

Monthly explosion of number Monthly 1/1 4/1 7/1 10/1 1/1 4/1 7/1 10/1 1/1 4/1 7/1 10/1 1/1 4/1 7/1 10/1 1/1 4/1 2008 2009 2010 2011 2012 Enlargement of Showa crater

Jan 2006 Sep 2011 Minamidake Minamidake

Showa 350m

Before eruptive activity Showa

May 2007 Minamidake

Showa Magma supply system of Sakurajima

1974-1992 (Vulcanian eruption) Since 1993 (Less eruptivity)

霧島 霧島 Magma discharge Magma accumulation

Aira caldera Aira caldera Sakurajima 姶良カルデラ 姶良カルデラ 鹿児島市 鹿児島市 Sakurajima 桜島 桜島

Magma reservoir Magma reservoir 5 5 マグマ溜り マグマ溜り 1× 107m3/ 年 1× 107m3/ 年 10 10

15 Supply rate 15 Supply rate 1x107m3/year 1x107m3/year 20 20 km km

Eruptive activity at Showa crater has not decreased magma in the reservoir yet. Location of VT earthquakes

1997-2010 (N=548) N

Magma reservoir

Aseismic zone

2012/2/21

W

Jan 12, 1914 M7.1 M 0 1 2 2010/7 2010/7 M 5km

M 0 5 10 W 2012/2/21 Depth (km) 0

2010/7 5

10 Depth (km) Long-term vertical displacement Volcanic ash (200 million tons) ejected from1974 to 1992 1914 eruption Violent explosivity of Minamidake

1946 eruption 30 years?

Inflation since 1993 28 years Aira caldera

31 years

FUTG SVOG

Recent inflation of Sakurajima KURG

measured by GPS ARIG

Minamidake Showa crater G PS連続観測による水平地盤変動 0.14 240 有村町-桜島二俣町（南北） 0.12 FUTG-ARIG(N-S) 200 0.10 160 0.08 120 0.06 80 0.04 Volcanic火山灰量 ash 0.02 40 0.00 0 199519961997199819992000200120022003200420052006200720082009201020112012 0.14 240 桜島横山町-黒神町（東西） 0.12 KURG-SVOG(E-W) 200 0.10 水平変動 (m) 水平変動 160 0.08

120

Horizontal displacement (m) displacement Horizontal 0.06 Number of 80 0.04 explosion爆発回数 0.02 40 0.00 0 199519961997199819992000200120022003200420052006200720082009201020112012 京都大学防災研究所 Ballistics South foot, Jul 21, 1985

Sakurajima

Showa crater

Minamidake

2km

3.5km Influence of volcanic ash fall Thickness of ash fall deposit by 1914 eruption

Many mud flows occurred after the 1914 eruption

Range of ash fall Mud flow (Minamidake eruption) （Omori, 1916) Dispersion of volcanic ash from Sakurajima volcano in 1914

Itami Fukuoka Narita Haneda Kansai Nagoya

Kagoshima

（Omori, 1916)

Airport 20km

Aira city Kirishima city

10km

Hioki city City hall 5km Sakurajima

Kagoshima city

Prefecture government

Kanoya city Tarumizu city