Earthquake size - Seismic Moment

Area (A)

Slip (S)

Seismic Moment = (Rigidity)(Area)(Slip)

)()(0 tuStM ∆⋅⋅= µ

Seismic moments and fault areasof some famous earthquakes

A Small Earthquake, M3.8

Reverse Fault

東西 吉田山

今出川通

北山通

鴨川

京大

Hanaore Fault花折断層

1 km

M3.8May 21, 2000

Fault Areas of Damaging Earthquakes

1944 TonankaiMw 8.1

1946 NankaiMw 8.1

1995 KobeMw 6.9

Source Areas of Large Earthquakes in Japan

Largest Recorded Earthquake1960 Chile earthquake

Mw 9.5Moment 2x1030 dyne-cmRupture Length ~1000 km

Recent Major Earthquakes in Japan

Date Name Location Magnitude DeathsSept. 1 1923 関東大震災 Tokyo 7.9 99,331May 23, 1925 北但馬 Tajima 6.8 428May 7, 1927 北丹後 Tango 7.3 2,925Nov. 26, 1930 北伊豆 Izu 7.3 272Mar. 3, 1933 三陸 Sanriku 8.1 3,064Sept.10, 1943 鳥取 Tottori 7.2 1,083Dec.7, 1944 東南海 Nankai 7.9 1,223Jan.13, 1945 三河 Mikawa 6.8 2,306Dec.21,1946 南海 Nankai 8.0 1,330Jun.28, 1948 福井 Fukui 7.1 3,769Mar.4, 1952 十勝沖 Tokachi-oki 8.2 28Jun.16, 1964 新潟 Niigata 7.5 26May 16, 1968 十勝沖 Northeast Honshu 7.9 52Jun. 12, 1978 宮城県沖 Miyagi 7.4 28May 26, 1983 日本海中部 Japan Sea 7.7 104July 12,1993 北海道南西沖 Southwest Hokkaido 7.8 202Oct. 4, 1994 北海道東方沖 East Hokkaido 8.1 10Dec. 28, 1994 三陸はるか沖 Sanriku 7.5 3Jan. 17, 1995 兵庫県南部 Kobe 7.2 6,310Sep., 26, 2003 十勝沖 Tokachi-oki 8.0 2

4. What controls the level of damage in an earthquake?

- Earthquake size

- Distance to the fault

- Site effects

Proximity to Populated Areas

World Seismicity（M>5, depth < 100km）

Attenuation Relations

Fukushima and Tanaka, 1990

Fault Areas of Damaging Earthquakes

1944 TonankaiMw 8.1

1946 NankaiMw 8.1

1995 KobeMw 6.9

5. Where do we expect the next large earthquake ?

Nankai earthquakes

Imamura, Tohoku Univ.

History of Nankai Earthquakes

Active Faults in Japan

Kyoto

Fault Areas of Damaging Earthquakes

1944 TonankaiMw 8.1

1946 NankaiMw 8.1

1995 KobeMw 6.9

Deaths

1944 12231946 13301995 6310

Kobe EarthquakeJanuary 17, 1995

Mw 6.9 (Mjma 7.3)Deaths 6310Injuries 26,797Damage ~$100 billion

2004 Niigata Chuetsu Earthquake

N

M6.3

0-20 20

0

-10

-20

10

20

Detail 1D'

D

Detail 2

EE'

M6.5M6.8

Detail 3

M6.0

FF'

M

M’ 0 2 4-15

-10

-5

0

6

C C'

Detail 1

M6.1

0 2 4 6

-5

0D

M6.5

Detail 2

D'

0 2

-5

0F F'

-15

-10Detail 4

0 2 4 6-15

-10

-5

0

Detail 3

E E'

M6.8

M6.0All B’B

M6.8 M6.5

M6.3

M6.1

M6.0

-20 -10 0 10 20