Summary on the great East
Japan earthquake and tsunami
Shoichi Yoshioka
Research Center for
Urban Safety and Security
Kobe University

・Summary on the great East Japan
earthquake
・Tsunami survey report
・Numerical simulations on tsunami（preliminary results）

・Summary on the great East Japan
earthquake
・Tsunami survey report
・Numerical simulations on tsunami（preliminary results）

来るべき東海・東南海・南海地震の想定震源域
Oceanicand continental plates in andaround the Japanese islands

Eurasia
plate

30 km
the great East Japan earthquake (M 9.0)

NorthAmericaplate

Japan trench
Pacific plate

PhilippineSea plate

80 km

time: March 11, 2011 14:46 (local time)
hypocenter: off the coast of Northeast Japan 30 km
lat. 138.0°N lon. 142.9°E
depth 24 km(modified from Shimazaki et al., 2002)
fault size: 450 km × 200 km

Generation mechanism of a trench-type
megathrust earthquake3
trenchcontinental plate(North Americaplate)oceanic plate(Pacific plate)strainaccumulation

generationof tsunami

Trench-type great earthquakes ever recorded in the world
1957 Aleutian earthquake
Mw 9.11952 Kamchatka earthquake
Mw 9.52011 East Japan earthquake
Mw 9.01964 Alaska earthquake
Mw 9.2
2004 Sumatra earthquake
9.1
Mw 9.02010 Chile earthquake
Mw 8.8

yearlocation
magnitude---------------------------------------------1960
Chile
Mw 9.5
1964 Alaska
Mw 9.21957 AleutianMw 9.1
2011 East Japan
Mw 9.02004 Sumatra
Mw 9.01952 Kamchatka
Mw 9.01960 Chile earthquake
Mw 9.5modified from ERI, Univ. of Tokyoseismic intensity scale in Japan
weakstrongweakstrong気象庁

jma_s.05.aviSpatial relation between the fault plane of the Sanriku-oki earthquake (March 9, 2011)
and the epicenter of the great East Japan earthquake

http://www.aob.geophys.tohoku.ac.jp/info/topics/20110311_news/

Aftershock distribution of the 2011 great East Japan earthquake
March 11, 2011 12:00－April 12 11:00
shallower than a depth of 90 km
M ≧5.0

AaBearthquake
headquarternews（２０１１)

Space-time plot of aftershocks in the area “a” (A-B projection)

Aftershock sequence in the area “a”

１０

Japan Meteorological Agency

2011 great East Japanearthquake (M 9.0)
TsukidateHitachi

1995 Kobe
Takatori earthquake (M 7.2)
Fukiai

Shiogama

Large effects onwooden houses

Furumura (2011)

Crustal deformation obtained by GPS associatedwith the main shock (M9.0)
horizontal component

Crustal deformation obtained by GPSassociated with the main shock (M9.0)
vertical component

subsidence of120 cm

水路部

http://www.gsi.go.jp/common/000059672.pdf

Geospatial Information Authority of Japan

GPS+
teleseismic
generationof tsunami

Simons et al. (2011)

Spatial distribution of observed tsunami heightEstimated slip distribution inmeters for each subfault

Maeda et al. (2011)

Tsunami waves recorded atoffshore ocean bottompressure gauge stations

Comparison of observed (black) and simulated(red) tsunami traces at stations
TM1 and TM2.

Horizontal movement
obtained by GPS
for three months
following
the main shock

Vertical movement
obtained by GPS
for three months
following
the main shock

Estimated slip distribution on theplate interface for three months
following the main shock

Geospatial Information Authority of Japan

・Summary on the great East Japanearthquake
・Tsunami survey report
・Numerical simulations on tsunami（preliminary results）

April 19, 2011 － April 23, 2011
MiyakoOfunatoRikuzen-takata
Kesennuma

MiyakoMiyako City Officetsunami protective wall

VIDEO

Rikuzen-takata

Land height above sea level in Rikuzen-takata

land height abovesea levelsea

shelter

1kmtsunamiIn general, behavior of tsunami at a V-shaped bay is ・・

Tsunami concentration
takes place at thebottom of a V-shaped
bay, and tsunami isamplified（Newton, 2011年6月号）
June, 2011

Serious damage caused by the tsunami isconsidered to have occurred at the bottomof the V-shaped baydeeply indented coastline (V-shaped bays)

Yoshihama Bay
Okirai Bay
Ryori Bay
Ofunato Bay
Hirota Bay

on-site tsunami height survey
April 20, 2011 － April 23, 2011

Shoichi Yoshioka
Kobe Univ.
Mamoru Nakamura Ryukyu Univ.
Kazuomi Hirakawa Hokkaido Univ.
Yuka Nishikawa
Taiwan Univ.
Ryoritsunami inundation height = 16.6m
tsunami run-up height = 23.82m

Rikuzen-takata (Horota Bay)tsunami inundation height = 14.3m

observed results（tsunami height）
for the bays with small
aspect ratio

yellow: this study
orange: other researchorganizationYoshihama Bay (R=0.9～1.6)

Okirai Bay (R=0.9～1.6)
Tsunami wave is amplified at thebottom of the bays with small aspectratio （about 1.5 times）

Ryori Bay (R=1.3～1.9)

R: amplification ratio（height at the bottom/height at the mouth）

observed
results
for the bay
with large
aspect ratio
yellow: this study
orange: other researchorganization

Hirota Bay (R=0.9～1.1)
Tsunami wave is not amplified at thebottom of the bay with large aspectratio

R: amplification ratio（height at the bottom/height at the mouth）Summary on observed results of tsunami height• On-site survey at Ofunato, Rikuzen-takata, andKesennuma―maximum height：Ryori（23.82m）• Amplification ratio of tsunami in the bays （height atthe bottom/height at the mouth） for the 2011
great East Japan earthquake– Bays with small aspect ratio：
0.9－1.9・・・・same or amplified at the bottom– Bays with large aspect ratio：
0.7－1.0・・・・no amplification at the bottom

・Summary on the great East Japanearthquake
・Tsunami survey report
・Numerical simulations on tsunami（preliminary results）
３０

fault size: 500 km×250 km slip: 17 m

Maeda and Furumura（2011）

the 2011 great East（秒）Japan earthquake

height（m）

30 min.

25 min.

length 400km、width 150km、amount of slip 15m
referred from Fujii et al. (2011) andMaeda et al. (2011)

Tsunami
maximum tsunami height（m）
height（m）
height for
40 min.
the 2011
great East
•Rikuzen-takata
2011年の津波
Japanearthquake• 湾の入り口沿岸と湾奥で波高が高い
35 min.

Tsunami ishigh along
the coastat thebottom of
the bay as
well as themouth of
the bay.

Tsunami height in the bays with small
aspect ratio– Tsunami is amplified at the bottom of the Ryori Bay– Variation of tsunami height at the mouth andbottom of the bay is small for the Yoshihama andthe Okirai Bays
– Tsunami might be high at the Ryori Bay due togeographical features prone to collect tsunami
effectivelyTsunami height in the bays with large
aspect ratio– Tsunami height at the bottom is almost thesame as that at the mouth

Thank you very much foryour attention