The Joint Symposium of Seismic Hazard Assessment
June 17, 2013, Trust City Conference, Sendai, Japan

Lessons learned from the 2011 Tohoku
earthquake for reducing earthquake disasters

Kojiro Irikura(NIED/ Aichi Institute of Technology/ Kyoto University, Japan)

Earthquake Disaster Prevention in Europe
The 14th century Assisi earthquake“Earthquake” by Giotto- God save us -GiottoEarthquake Disaster Prevention in Japan
Pictures of the 1855 Edo (Tokyo) Ansei Earthquake (M6.9）- Battles against underground catfishes -Today’s Topics
1. Outline of damage during the 11 March 2011 Mw 9.0
Tohoku, Japan earthquake
2. National seismic hazard in Japan before and after theearthquake
3. Early Warning of Strong Shaking and Tsunami by JMA
4. Short‐period source model of the 11 March 2011 Mw 9.0
Tohoku earthquake estimated from strong motion data
5. Period‐dependence of rupture processes
6. Recipe of predicting strong ground motions for subduction
megathrust earthquakes
7. Summary

1. Outline of damage during the 11 March 2011 Mw 9.0
Tohoku, Japan earthquake

Daiichi

Fatalities 13,135
Drowning 2,143 (92.5 %)Missing 3,279
Victim’s age > 60 65.2 %> 70 24 %Destroyed Buildings 45,700
Miyagi 29,500 Iwate 12,500
Fukushima 2,400
Damaged Buildings 144,300

After “Japan’s Challenge Towards Recovery”, March 2012, METI

March 11, 2011 tsunami
Miyako, Iwate pref.
~30 min after the eq.
Large (~ 30 m) tsunami
height along Sanriku
coast
Mainichi Newspaper

Natori, Miyagi pref.
~ 1 hour after the eq.
Long (~5 km) inundationin Sendai plainAP

Satake (2012)

7

Comparison of 2011 Tohoku with Past Tsunami
1933~1896~2011

1933< 1896~2011

1933~1896 < 2011

After Satake (2012)

NPPs in Eastern Coast of Japan
Onagawa(Tohoku)

Fukushima
Daiichi *(TEPCO)

Fukushima
Daini(TEPCO)

Tokai-2(JAPCO)* Fukushima Daiichi locates approximately
9
230 km north of Tokyo

Onagawa Nuclear Power Station(very little damage by tsunami )Attached Building ofUnit 2 （sea water
influx）
Fuel Oil Tank of
Unit 1 （colapse）

Tsunami Height：about13ｍ
Arrival Time of Maximum Tsunami：15:29, 11 March

Site Height：13.8ｍ

Accident at Fukushima Nuclear Power Station

2. National seismic hazard before and after the 2011
Tohoku earthquake“National Hazard Maps” in Japan have been published by
the Headquarter of Earthquake Research Promotion since 2005.
Long‐term evaluation of earthquake occurrence has been made nation‐wide
for inland crustal earthquakes, subduction earthquakes and intraslab
earthquakes including the source region of the 2011 Toh0ku earth.

Strong ground motion evaluation has been made using prpbabilistic anddeterministic approaches.

Tsunami assessments have been made for specific past disastrous
earthquakes by Central Disaster Management Council.

Probability of Earthquake Occurrence in 30 years
Inland Crustal‐Earthquakes

Subduction Earthquakes

Headquarter of Earthquake Research Promotion (2010)

National Seismic Hazard Map for Japan and Regions
for Long‐term Forecast along Subduction Zone
Recurrence of large earthquakes along
Japan trench

NIED (2011)

Revision of long‐term evaluation of seismic activity forthe region from the off Sanriku to the off Boso ,(Earthquake Research Committee , 25 Nov. , 2011)
Earthquakes with the same type as the 2011 off the Pacific coast of Tohoku
Earthquake
Past Activity
5 times for past 2,500 years
2011 M 9.0 earthquake
15 century from Tsunami deposits
869 (the Jogan earthquake) from a history book
4 to 5 centuries from Tsunami deposits
3 to 4 centuries B.C. from Tsunami deposits
 Return periods
400 – 800 years
average period 600 years
 Probability of earthquake occurrence before the 2011 earthquake
10 – 20 % in 30 years

Probabilistic Seismic Hazard Map in 2011 (HERP, 2012)
Probability of ground motions more than JMA intensity 6-lower within 30 years

Without Mw 9 earthquake

Probability

With Mw 9 earthquake

Probability

Influence of Mw 9.0 earthquake on Probabilistic Seismic Hazard Map in 2011
With M9.0 earthquake

Difference between PSHM with M 9.0
and that without M 9.0

Probability

Probability

Maximum JMA intensity with more than 2 % probability
within 50 years in 2011
Comparison between estimated ones and observed ones during the 2011 Tohoku
earthquake
Without M 9.0 earthquake

With M 9.0 earthquake

Observed

Observed

7
6 higher
6 lower
5 higher
5 lower43

JMA intensity

7
6 higher
6 lower
5 higher
5 lower43

JMA intensity

3. Early Warning of Strong Shaking and Tsunami by JMA

Japan Meteorological Agency is in charge of issuing warning
information about strong shaking and tsunami as quickly as
possiblehave whenever an earthquake occurs.


Earthquake Early Warning System

Tsunami Warning and Evacuation

Earthquake Early Warning from JMA during the 2011 Tohoku earthquake

Sequence of determining magnitude in
the JMA FEW
14:46:48.8

Origin time: 14:46:23

Earthquake Early Warning from JMA during the 2011 Tohoku earthquake
Observed Intensity (JMA)

Final warning M 8.1
105.0 sec after first P‐wave detection
Estimated Intensity (JMA)Why were people not able toevacuate for devastating tsunamis ?
What problems did the JMA tsunami warning
system have?
What unrecognized factors contributed to thehigh vulnerability of the area ?
大渋滞
公民館
閖上中学
過去の経験：1960チリ津波
避難の拒否
After Imamura (2012)22

Sequence of the tsunami warning after the Tohoku earthquake
The earthquake occurred at 14:46:23 JST (UTC +09.00)

23

8m

Tsunami Warning Sequence

3m

1m（Aomori〜Fukusima along the
Pacific coast）

8m
3m

1m

Aomori

6m

10m以上

3m
10m以上

★3/11 14:46 地震発生
①3/11 14:49 津波警報の発表
14:50 岩手3m,宮城6m,福島3m（大津波）
青森県太平洋沿岸1m（津波）6m②3/11 15:14 津波警報の更新
岩手6m,宮城10m以上,福島6m、青森県太平洋沿岸3m（大津波）

3m

Iwate
10m以上
6m

③3/11 15:30 津波警報の更新
15:31 岩手〜千葉九十九里･外房10m以上、青森県太平洋沿岸8m（大津波）

3m
10m以上
6m

気象庁提供
10m以上

Miyagi6m
3m

6m

Fukushima

10m以上

3m
★

①

②

③

潮位観測データ（実況監視していた
もの）潮位観測データ（データ断となり後日回収されたもの）
潮位観測データ（データ断）
津波の高さの予想

14:49
Mj7.9

14:58
PTWCよりM7.9

15:40頃
Mw8.8を推定 15:43
PTWCよりM8.8

After Imamura (2012)24

4. Short‐period source model of the 11 March 2011
Mw 9.0 Tohoku earthquake estimated from strong
motion data
 Five distinctive wavapackets were detected on strong motion
sesimograms at stations near the source fault.
 The arrival azimuths of those wavepackets were estimated using
the semblance analysis in several small arrays.
The locations of strong motion generation areas (SMGAs) arecoincident with the origins of those wavepackets.

Re‐estimation of Locations of SMGAs from Semblance Analysis of Wave‐
Packets seen in Short‐Period Seismograms
Wave pachet 2

Wave packet 3
Wave packet 4
Wave packet 1

Wave packet 5

After Irikura and Kurahashi (2011)

Mini-arrays (A, B, C, D, E, F, and G)
for estimating arrival azimuths of wave-packets

Particle Motion Diagrams (Vertical) of WP1 at 3 Stations
in Array B

Semblance Analysis for Wave Packets
using Local Arrays
R1/Vs
STN1

STN2
STN3

R2/Vs

Simulation of Strong Ground Motions during the 2011 Tohoku
Earthquake Using the Empirical Green’s Function Method

 Strong Motion Generation Areas are relocated using the semblance

analysis of the wave-packets in small arrays.
 The observed data from medium-sized earthquakes occurring near eachstrong motion generation area are adopted as the empirical Green’s
functions.
 Strong motion records of the 2005 Miyagi-Oki earthquake (Mw 7.2) areused as the empirical Green’s functions for SMGA1 (WP1) and SPGA3(WP2).

Revised Model

SMGA2
SMGA1
SMGA3

SMGA4

SMGA5

L,W

Mo

Stress drop

SMGA1

34×34

2.68E+20

16

SMGA2

23.1×23.1

1.41E+20

20

SMGA3

42.5×42.5

6.54E+20

20

SMGA4

25.5×25.5

1.24E+20

25.2

SMGA5

38.5×38.5

5.75E+20

25.2

Comparison of Observed and Synthsized （SMGA1,2,3のみ）

MiyagiOnagawasite

黒：Obs.
赤：Syn.

Acceleration Records with remarkable distictive pulses
Horizontal NS

Horizontal EWHeterogeneity of stress parameters inside SMGA

Period range of ground motions generated from the SMGAs

 Longer-period motions from the Strong Motion Generation
Areas (SMGAs) are estimated using numerical Green’s
functions: the Discrete Wavenumber method (Bouchon,1981) and the Reflection/Transmission coefficient matrix
method (Kennet, 1983) using a stratified medium.
 Effective period range of ground motions generated fromthe SMGAs are confirmed by comparing simulated motions
with observed motions.
 Verification of the fault parameters are made, mainly inner fault
parameters of Strong Motion Generation Areas (SMGAs)
estimated using the empirical Green’s function method

Comparison between slip distribution using long‐period
motions (Suzuki et al, 2011) and SMGAs in this study

Slip distribution inverted fromlong‐period motions filtered0.01‐125Hz (100 – 8 s)

SMGAs estimated from short‐period
motions filtered 0.15‐10Hz (6.6 – 0.1 s)

Initial models of velocity structures
 Surface layers models: P‐S logging data in boreholes (Kik‐net and
K‐NET)
 Shallow layers model less than 5 km: Velocity structure models
determined by NIED.
 Deeper layers model more than 5 km: Velocity structure model by
Wu et al.(2008)
Velocity structure model inshallow layers (Kik net)

Velocity structure modelin deeper layers

Frequency Range
0.05‐1Hz
Observed
Fitting Observed to Calculated Motions from Small Events
Synthetic
2.E‐03
1.E‐02観測計算

1.E‐030.E+00
0

10

40

計算

0.E+00
0

10

20

30

40

‐1.E‐03‐2.E‐03

Velocity Fourier (cm/s*s)

観測

MYGH04 EW

1.E‐05
1.E‐06
1.E‐072.E‐03

観測

MYGH04 UD計算

1.E‐030.E+0001020‐1.E‐03

Time(sec)

1.E‐02

30

40

0.1
1
Frequency(Hz)

MYGH04 EW

1.E‐03観測
計算

1.E‐04
1.E‐05
1.E‐06
1.E‐070.01

Time(sec)

観測
計算

1.E‐040.01

1.E‐03‐2.E‐03

MYGH04 NS

1.E‐03

Time(sec)

2.E‐03
Velocity(cm/s)

30‐1.E‐03‐2.E‐03

Velocity(cm/s)

20

Velocity Fourier (cm/s*s)

Velocity(cm/s)

MYGH04 NS

Velocity Fourier (cm/s*s)

Identification of Velocity Structure Model

1.E‐020.1
1Frequency(Hz)

MYGH04 UD

1.E‐03
1.E‐04
1.E‐05
1.E‐06
1.E‐070.01

0.1
1Frequency(Hz)観測計算

Velocity Structure Models (Vs）
1-D velocity structures from stations to source are modeled comparing synthetic motions withobserved ones from small events.

MYGH06Vs
S波速度(km/s)

MYGH04Vs
S波速度(km/s)
0

2

3

4

5

2

3

4

5

0

100

100

100

200

200

200

300

300

300

400

400

400

500
600

700

700

800

800

修正モデルVs
Identified

900

初期モデルVs
Initial1000

0

S波速度(km/s)
2
4

深さ(m)

0

600

0

速度(km/s)
2
4

6

0

5

5

10

10

10

15

15

15

20

20

20

45
50

深さ(km)

5

40

25
30
35

修正モデルVs
初期モデルVs

40
45
50

5

1000

0

35

4

修正モデルVs
初期モデルVs

900

0

30

3

600

0

25

2

500

800

修正モデルVs
初期モデルVs

1000

6

1

700

900

深さ(km)

深さ(km)

1

0

500

Deep
Structure

0

0

深さ(m)

深さ(m)

Shallow
Structure1

MYGH08S波速度(km/s)
Vs

S波速度(km/s)
2
4

25
30
35

修正モデルVs
初期モデルVs404550

修正モデルVs
初期モデルVs

6

Comparison between Observed and Synthetic Motionsin Miyagi Prefecture
Frequency Range
0.05 – 1.0 Hz

Observed
Synthetic

Comparison between Observed and Synthetic Motions
in Fukushima Prefecture
Frequency Range
0.05 ‐ 1Hz

Observed
Synthetic

Comparison between Observed and Synthetic Motionsin Kanto Region Frequency Range
Observed
0.05 ‐ 1Hz

CalculatedComparison between Observed and Synthetic Motionsin Miyagi Prefecture
Frequency Range
0.01 ‐ 0.1Hz

Observed
CalculatedComparison between Observed and Synthetic Motionsin Miyagi Prefecture
Frequency Range
0.01‐1Hz

Observed
Synthetic

Comparison between Observed and Synthetic Motions
in Fukushima Prefecture
Observed
Frequency Range
0.01‐1Hz

Synthetic5. Period‐dependence of rupture processes– comparison of short‐period source model and long‐period
source models inverted long‐period strong motion data,tsunami waveforms, geodetic data ‐ Short‐period source models using backprojection of teleseismic
short‐period P‐waves
 Long‐period source models inverted from tsunami data (Fujii etal., 2012) , geodetic data (Iinuma et al., 2012) and joint data
(Yokota et al.)Comparison of Short‐Period Source Model in This Study with Short‐Period Released
Energy by the back‐projevtion method
US Array Data by Ishii (2011)

Kanto Array Data by Hoda et al, (2011)

Slip Distribution of the 2011 Tohoku Earthquake
DPS data including inland andoff‐shore observation

Geographical Institute (2011)

Tsunami Waveform Data

Fujii and Satake (2011)

Patterns of Coherent Short‐period radiation and Large Slip Regions for
Mega‐thrust Earthquakes

Modest slip, strong short‐period radiation
Large slip, weak short‐period radiation and strong tsunami generation
Lay, et al. JGR(2012)

6. Recipe of predicting strong ground motions for
subduction-zone megathrust earthquakes
 Rupture process of subduction‐zone megathrust earthquakes show
period‐dependence.
 New source image for period‐dependent source process isexpressed as multi‐step heterogeneous‐source‐model.
 Strong ground motions of engineering interest in the period‐range
from 0.1 to 10 sec are estimated using the basic characteristic source
model with outer‐fault parameters and inner fault parameters,that is, just one step heterogeneity source model.

Multi‐Step Heterogeneous
Source Model ‐ 1
Second step: Heterogeneity model
for very short‐periods
0.05 – 0.2 sFirst step: Heterogeneity model
for short periods 0.1 – 20 s

Multi‐Step Heterogeneous Source Model ‐ 2Third step: Heterogeneity model
for long periods 10 – 100 s

Suzuki et al. (2011)

Heterogeneous Model for Broad-band Motions from 0.1 to 10 s
The SMGAs are locatedalong outer edge of thelarge slip delineatedbased on the seismicity
rate (Kato and Igarashi,
2012)Comparison between SMGAs in this study and source locationsof past earthquakes off the Pacific coast of Tohoku

Basic Characterized Source Model
Step 1: Heterogeneous Model for Broad-band Motions
from 0.1 to 10 sec-

Comparison between observed and synthetic waveforms
in the region near the source fault (Miyagi and Onagawa)Comparison of Seismic Intensity
between Observed and Synthetics
Iwate
岩手
Pref.

6

Miyagi Pref.
宮城

7

Synthetics
計算震度

Synthetics
計算震度

7

5
4
3
2

6
5
4
3
2
1

1

0

0
0

1

2

3

4

5

6

0

7

1

観測震度
Observed

4

5

6

7

6

7

Ibaragi Pref.
茨城

76

Synthetics
計算震度

Synthetics
計算震度

6

3

観測震度
Observed

Fukushima
福島
Pref.

7

2

5
4
3
2

5
4
3
2
1

1
0

0
0

1

2

3

4

観測震度

5

Observed

6

7

0

1

2

3

4

観測震度

5

ObservedSummary 1
1. This earthquake on the plate boundary along the Japan
trench produced a devastating tsunami and caused about
16,500 fatalities (including missing) and serious damage tonearby Fukushima nuclear power plants.
2. The size of the maximum earthquake based on thecharacteristic earthquake model was underestimatedas M ~ 7.5, while the epicenter was near Miyagi-oki, where
the probability of earthquake occurrence was evaluated as
the highest (99 % in the next 30 years) in Japan.
3. From the forward modeling of the source model for
simulating short-period ground motions such as
acceleration and velocity seismograms, there are five
SMGAs over the source fault located west of the hypocenterand along the down-dip edge of the source fault.

Summary 2
4. Synthetic motions from the SMGAs match well with observed
motions in the period-range from 0.1 to 10 sec.
5. Period-dependence of rupture process was found, that is large
slips in shallow zones of the source fault near the trench westof the hypocenter and short-period generation in deeper
zones west of the hypocenter.
6. Strong ground motions of engineering interest in the periodrange from 0.1 to 10 sec are estimated using the characteristic
source model with outer-fault parameters and inner fault
parameters as the recipe of predicting strong ground motions
for subduction earthquakes.