Volcanic activity of Sakurajima volcano, South Kyushu, Japan

Masato Iguchi

Sakurajima Volcano Research Center, DPRI, Kyoto Univ.

2012/5/18

Sakurajima

Unzen

Aso

32N

30N

130E

132E

Satsuma-Iwojima

Suwanosejima

Volcanoes in Kyushu

Kirishima Volcano Complex

Kaimondake

Kuchinoerabujima

Nakanoshima

110 volcanoes in Japan

Japan Sea

Russia

Japan

Korea

Pacific Ocean

2011 Eruption at Shin-moedake of Kirishima Volcano Complex

Mr. Shimousuki, Kagoshima International Aviation

Deflation due to sub-plinian eruption

on January 26, 2011

Quick turn to inflation inflation

Slope distance change

Sub-plinian eruption on January 26, 2011 Lava dome

Historical eruption of Sakurajima

1914

1914

1779

1779

1471-76

1471-76

1946

764

764

1471-

1476

1779

1914

500

1000

1500

2000

AD 0

Minamidake

Kitadake

Showa crater

Submarine eruption

in 1780

Historical eruptions

Bunmei

eruption

An’ei

eruption

Taisho

eruption

Showa

eruption

1471-76 1779-80 1914 1946

Vent location NE-SW N-S E-W E

Volume of

lava (km3)

0.5 1.7 1.34 0.18

Volume of

tephra (km3)

0.7 0.4 0.52 0.02

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

Showa crater

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

0

1000

2000

3000

1977年 以 前 は 測 定 なし

火山灰量（万トン）

年間爆発回数

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

0

200

400

600

800

1000 南岳爆発回数 昭和火口爆発回数

2012年

3月まで

Annual number of explosion

Minamidake crater

Annual weight of volcanic ash

(million ton)

30

20

10

No measurement before 1977

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

0

50

100

150

200

250

300

空気

振動

振幅

(Pa)

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

0

20

40

60

80

100

120

140

160

180

200

月別爆発回数

2008 2009 2010 2011　　　　　2012

0

500

1000

1500

2000

2500

3000

3500 積算回数

積算回数

Increase in eruptive activity The first explosion on

February 3, 2008

Increase in

eruptivity

Increase in

eruptivity

April 9, 2009

Pyroclastic flow

Explosion at Minamidake

October 3, 2009

Lava dome in crater

JMA

Month

ly n

um

ber

of explo

sio

n

Cum

ula

tive n

um

ber

Showa

Enlargement of Showa crater

May 2007

Jan 2006 Minamidake

Showa

Minamidake

Showa

Minamidake

Before eruptive activity

Sep 2011

350m

5

10

15

20km

霧島

鹿児島市

姶良カルデラ

桜島

マグマ溜り1× 107m3/年

5

10

15

20km

霧島

鹿児島市

姶良カルデラ

桜島

マグマ溜り1× 107m3/年

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

Magma discharge Magma accumulation

Magma supply system of Sakurajima

Aira caldera

Sakurajima

Aira caldera

Sakurajima

Supply rate 1x107m3/year

Supply rate 1x107m3/year

Eruptive activity at Showa crater has not decreased magma in the reservoir yet.

Magma reservoir Magma reservoir

Location of VT earthquakes

10

5

0

0 5 102012/2/21

2012/2/21

2010/7

2010/7

N

5km

M 0 1 2

1997-2010 (N=548)

2010/7 M

W

W

Depth (km)

Depth

(km

)

M

Jan 12, 1914 M7.1

Magma reservoir

Aseismic zone

Long-term vertical displacement

1914 eruption

1946 eruption

Violent explosivity of Minamidake

Volcanic ash (200 million tons) ejected from1974 to 1992

31 years

28 years

30 years?

Inflation since 1993

Aira caldera

Recent inflation of Sakurajima measured by GPS

SVOG KURG

ARIG

FUTG

Minamidake Showa crater

1995199619971998199920002001200220032004200520062007200820092010201120120.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14199519961997199819992000200120022003200420052006200720082009201020112012

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0

40

80

120

160

200

240

0

40

80

120

160

200

240

爆発回数

桜島横山町-黒神町（東西）

京都大学防災研究所

G PS連続観測による水平地盤変動

水平

変動

(m)

有村町-桜島二俣町（南北）

火山灰量

Horizonta

l dis

pla

cem

ent

(m)

FUTG-ARIG(N-S)

KURG-SVOG(E-W)

Volcanic ash

Number of explosion

Ballistics

Sakurajima

Minamidake

Showa crater

3.5km

2km

South foot, Jul 21, 1985

Influence of volcanic ash fall

Thickness of ash fall deposit by 1914 eruption

Range of ash fall

（Omori, 1916)

Many mud flows occurred after the 1914 eruption

Mud flow (Minamidake eruption)

Dispersion of volcanic ash from Sakurajima volcano in 1914

（Omori, 1916)

Haneda

Narita

Kagoshima

Nagoya

Itami

Kansai

Fukuoka

Airport

20km

10km

5km City hall

Prefecture

government

Tarumizu city

Kirishima city

Kanoya city

Sakurajima

Aira city

Kagoshima city

Hioki city