Seismic hazard assessment for Japan after
the 2011 Great East Japan Earthquake

Hiroyuki Fujiwara
National Research Institute for Earth Science and Disaster Prevention

National seismic hazard maps for Japan	
Long term evaluation	

Strong-motion evaluation	

Probability of occurrence, magnitude, location	

Strong-motion, underground structure	Probabilistic Seismic Hazard Maps

Scenario Earthquake Shaking Maps	

・Showing the strong-motion
intensity with a given
probability, or the probability
with a given intensity.

・Showing the strong-motion
intensity around the fault
for a specified earthquake.

・Considering all possible
earthquakes.

	Evaluation of occurrence probability of earthquakes
by ERCJ	Flowchart of PSHA
Modeling of seismic activity

Evaluation of an EQ occurrence probability P(Ei)Probabilistic evaluation of an intensity level P(Yi > y|Ei)
Evaluation of probabilistic seismic hazard
for each earthquake P(Yi > y)= P(Ei) P(Yi > y|Ei)
Evaluation of probabilistic seismic hazard
for all earthquakes P(Y > y)=1-Π[1- P(Yi > y)]Probabilistic Seismic Hazard Maps

Probability in 30 years.
(≧JMA Seismic Intensity 6-） 	

Seismic Intensity with 3% probability ofexceedance in 30 year.

Scenario Earthquake Shaking Maps	
The shaking maps are evaluated for 490 scenario earthquakesof almost all of major faults in Japan.	

Selection of a specified scenario is essential to make a shaking map. The basic policy of the selection of a
scenario earthquake is that we choose the most probable case.
For treatment of uncertainties, we assume several cases of source model and compare the results of them toshow deviation of strong-motion evaluation due to uncertainties.

Theoretical approach for evaluationof strong-motion
Amplification due to soft soil near surface

Complicatedsource process

Wave propagation in aheterogeneous medium

Amplification due tothick sedimentHybrid method for evaluation of strong-motion
Low frequency range

Matching filterLowfrequency
range

High
frequency
range

Finite Difference Method

High frequency range

Stochastic Green’s function method

Superposition

deterministic

Stochastic

The technical details on the hybrid method are summarized as the‘Recipe for strong-motion evaluation’, which are published by theearthquake research committee of Japan.	

Characterized Source Model
Complicated source model

The complicated source model is simplified by thecharacteristic source model for strong-motion prediction.
Characterized source models are composed of asperities and abackground slip area surrounding the asperities. Asperities are
the main rupture areas in the fault zone.
Source parameters required to evaluate strong-motions byusing the characterized source model are classified into threeparts.
The first part is the set of outer parameters that show themagnitude and the fault shape of the earthquake.
The second part is the set of the parameters that describe thedegree of fault heterogeneity.
The third part is the set of the parameters to define thecharacteristics of the rupture propagation.

Modeling of underground structure
Surfacesoil

Seismic bedrock（Vs=3km/s）	

•The deep underground structure from the crust andplates up to seismic bedrock;•The structure of sediments from the seismic bedrock
up to engineering bedrock (Vs=400m/s～700m/s);•The structure of surface soils from the engineering
bedrock up to the ground surface.
Flowchart of structure modeling

Sediment

SourceDeep undergroundstructureEngineering bedrock（Vs=0.4～0.7km/s）	

Site Amplification	2005～2008	

2009	

390,000 meshes	

5,960,000 meshes	

Mesh size	
 
1km2	
 

Mesh size	 Site Amplification	

0.25×0.25km	
 Site Amplification	

Development of Integrated Geophysical and Geological Information Database 	
Information on underground structure	

38.5

8000
7000
6500
6000
5500
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
400
300
200
100
50
0

38.33

38.17

38

37.83

37.67

37.5

37.33

37.17

37

36.83

137.67 137.83

138138.17 138.33

138.5

138.67 138.83

139

139.17 139.33

139.5

139.67

Management system on sharing for Integrated Database	
NIED
Database ofunderground structure

AIST
Database ofgeological information	

PWRI
Database ofsoil dynamics	

Coordination and integrationby the network
Municipalitie’sDB

Utilization of the database	

ERI of
Tokyo University	

Tokyo Institute ofTechnology

Reduction of natural disaster
Construction of safe, secure and sustainable society 	JGS’s
database	The concept of Integrated Database
Image of Integration
Integration of data
contents from the original data
to model data
Integration of databases ofmultiple organizations

Integration of data
across the country

Integration byshared management
via the network
Integration in terms of
depth from the shallow
part to the deep part

Qualitative integrationof information on geology,
geophysical data, etc.

As we regards information on underground structure as ‘public assets of the nation’, we develop a
database that allows for mutual utilization and publication of data through a network of eachorganization’s databases. The keyword of this research project is ‘Integration’. The word ‘Integration’implies several meanings, as shown in this figure, the process of integration is to be carried out
following these six principles.	

Diagram showing the concept of the management system on sharing
Search function, Map display function, Download
function

User

Applicable software: Browser, GIS

Image, GML

Portal site （NIED）	
WMS: Web Map Service
WFS: Web Feature Service

Internal user

Existing
systemService integration, Data integration

Image, GML		

Image, GML

Image, GML

Image, GML

WMS, WFS server(Example: MapServer)

WMS server	
WFS server	

WMS server	
WFS server	

WMS server	
WFS server	Spatial database(Example: PostGIS)

Spatial database	

Spatial database	

Spatial database	Database(Example: PostgreSQL)
Spatial information
and attributes

Upgrading adapter

Internal user

Existing
system

Database		

Spatialinformation
and attributes

Upgrading adapter

Internal user

Existing
system

Database		

Spatialinformation
and attributes

Internal user

Spatialinformation
and attributes

Existing
systemUpgrading adapter

Database		Upgrading adapter

Database A

Database B

Database C

Database D

NIED (Head office)

AIST

PWRI

Municipality

Working group (Venue to discuss utilization and publication of data)

The configuration of the data sharing management system consists of database management
servers for individual organizations and a portal site.	

Boring data collected and registered into database
機関	
 
国	
 

本数	
 
142,492	
 機関内訳	
 国土交通省	
 本数内訳	
 90,542	
 文部科学省（防災科研を含む）	
 51,950	
 北海道地方	
 
東北地方	
 
関東地方	
 
北陸地方	
 
中部地方	
 
近畿地方	
 
中国地方	
 
九州地方	
 
北海道内	
 
青森県内	
 
岩手県内	
 
秋田県内	
 
山形県内	
 
福島県内	
 
茨城県内	
 
栃木県内	
 
埼玉県内	
 
千葉県内	
 
神奈川県内	
 
新潟県内	
 
富山県内	
 
石川県内	
 
福井県内	
 
静岡県内	
 
岡山県内	
 
広島県内	
 
山口県内	
 
徳島県内	
 
香川県内	
 
福岡県内	
 

11,242	
 9,397	
 87,511	
 8,359	
 23,475	
 15,580	 12,637	
 1,446	
 
315	
 
268	
 
493	
 
179	
 
741	
 
340	
 
24	
 
777	
 
1,560	
 2,196	
 28,857	
 1,020	
 199	
 4,201	
 
342	
 
830	
 
218	
 
194	
 
585	
 
128	
 
595	
 
13	
 

学会・協議会関係	
 107,511	
 旧公団・公社等	
 地盤図等	
 3,652	
 10,844	
 都道府県	
 169,647	
 市町村	
 44,075	 その他	
 122,007	
 合計	
 478,221	
  	
 

	
 

The number of boring datathat have been registered in
the database is approximately
480,000 across the country. 	

Japan Seismic Hazard Information Station
http://www.j-shis.bosai.go.jp
In order to promote the use of the national seismic hazard maps, an engineering applicationcommittee (Chairman: Prof. H. Kameda) was established by NIED. Under the committee guidance,
we developed an open web system to provide information interactively, and named this system asJapan Seismic Hazard Information Station, J-SHIS.
Our products are aimed to meet multi-purpose needs in engineering fields by providing informationof the probabilistic seismic hazard analysis.

Japan Seismic Hazard Information Station

http://www.j-shis.bosai.go.jp

The 2011 Tohoku-oki earthquake 	
This magnitude 9.0 megathrust earthquake
initiated approximately 100 km off-shore of
Miyagi prefecture and the rupture extended
500 km along the subducting Pacific plate.
Due to the large ground motions and tsunami
associated by this event, approximately
20,000 people were killed or missing andmore than 220,000 houses and buildings
were totally or partially destroyed.
The Tohoku-oki earthquake was the firstM9-class earthquake that is closely recorded
by dense seismograph network.
The ground motions were recorded at morethan 1200 K-NET and KiK-net.
The peak ground accelerations (PGA)
exceeded 1g at 20 sites and the largest PGA,
2933 gal was observed at the K-NET
Tsukidate station (MYG004).

Paste-up of the observed waveforms	
Acceleration EW component	Displacement (0.02-1 Hz) EW component	Normalized acceleration and displacement (0.02 - 1.0 Hz) paste-up of the waveforms observed by K-NET and KiK-net
ordered by latitude which reveal a very complex source process; An initial strong phase originating near the hypocenter isclearly observed. A subsequent seismic phase uniformly delayed by approximately 40s suggests a second event at nearly
the same location. A later seismic phase is strongly observed to the south 50 - 60 s after the initial phase. This phasesuggests that a third strong event took place off-shore of Fukushima-Ibaraki. 	

Source rupture process estimated from strong-motion records	

○ Results- Large slip area extends from a region around the hypocenter to theshallower part of the fault plane.
- The largest total slip of 25 m is estimated near the trench of far off thecoast of Miyagi prefecture.
- The main rupture started 20 seconds after the initial rupture at the area
situated up-dip from the hypocenter and propagated to the north for 30
seconds. Large slip occurred again near the area where the main rupture
started after 60 to 80 seconds.
- Seismic moment is 3.43×1022 Nm (Mw9.0)

Suzuki et al. (2011)	

Comparison between the hazard maps and observed strong motions	Comparison between the observed seismic intensities（○：K-NET, △：KiK-net）of the Tohoku earthquakeand seismic intensity distribution for 2% probabilityof exceedance in 50 years, which is one of theprobabilistic seismic hazard map.
As you can see from this comparison, predicted
ground motion level in the probabilistic seismic
hazard map was clearly underestimated in Fukushima
Prefecture and the northern part of Ibaraki Prefecture
for the Tohoku-oki earthquake (M9.0).

7
6+
65+
54
3 or less	

seismic intensity	

Seismic Intensity with 2% probabilityof exceedance in 50 year.	

This is primarily because, in the long-term evaluationthat has been the basis of the seismicity model for the
probabilistic seismic hazard map, the occurrence ofgreat earthquakes M9.0 has not been evaluated.
On the other hand, the cause of underestimate alsolies in the inability to function well the wholeframework of probabilistic seismic hazard assessment
methods under the circumstances that many issues
are left unresolved in seismology.

Modeling of seismic activity in the Pacific plate
before the 311 Tohoku earthquake	

M=8.0      6%M=7.5    >99%

M=7.7    81%

Mu=7.0?
	

Mu=7.0Mu=7.2
Mu=7.5
Mu=7.1

M=7.4    7%Mu=7.5
M=8.2      5%Mt=8.2    20%

M=7.0    99%

?
	M for characteristic earthquakes

Mu=7.3

Mu=7.0Max M for background earthquakes

Seismic activity model for hazard assessment	
Earthquakes with specified fault	
Earthquakes in major or other fault zones	
Earthquakes in subduction zones(Interplate or intraplate)	
Background earthquakes	
Inland earthquakes	
Earthquakes in subduction zones(Interplate or intraplate)	
In order to construct a probabilistic seismic activity model that encompasses the seismic activity of all
possible earthquakes, it is necessary for the complement the long-term evaluation to use a different
methodology.
It may be necessary to promote proper modeling of background earthquakes that encompasses all
earthquakes without long-term evaluation.	

Classification of uncertainty factors	
● Aleatory Uncertainty
・ Intrinsic uncertainty.

・ It is represented by a random variable in the prediction model.	
・ Uncertainty caused by a limitation of model to explain phenomena.
・ Uncertainty used to calculate a hazard curve.

● Epistemic Uncertainty
・ Uncertainty due to a lack of knowledge and data.
・ Uncertainty due to differences in judgment for modeling	
・ It is evaluated by using a logic tree.
・ Represented by more than one hazard curve.	

Problems that must be overcome for
improvement of seismic hazard assessment	1) Modeling of seismic activity with no oversight to
low-probability earthquakes.	
2) Preparation of strong ground motion maps
considering low-probability earthquakes.	
3) Development of methodology for selecting
appropriate scenario earthquakes from probabilistic
seismicity model.	
4) Development of methodology for prediction of strong
ground motions for mega-thrust earthquakes.	

Seismic activities in the Pacific plate	

No.1（G-R law）	
No.2

It may be necessary to promote proper modeling of
background earthquakes that encompasses all
earthquakes without long-term evaluation.
For example, it may be possible to evaluate the magnitudeof earthquakes from the area of ​the plate boundary thatcan be considered to cause earthquakes, and to assess
the frequency of occurrence of earthquakes by using the
Gutenberg-Richter formula that shows the relationshipbetween the number of earthquakes and their magnitude.

Modeling of seismic activity in the Pacific plateafter the 311 Tohoku earthquake	

M=8.0      7%M=7.4    (55%)

M=7.9      0%Mu=7.0?
	

Mu=8.0  or  8.2Mu=8.0  or  8.4Mu=8.0  or  8.4M=7.4    14%M=8.2    5%Mt=8.6-9.0  25%

M=7.0    95%

?
	M for characteristic earthquakes

Mu=8.0  or  8.2Mu=8.0Mu=8.0  or  8.3Mu=8.0  or  8.3Intraplate
Mu=7.5 or 8.2	Max M for background earthquakes(Model 1 or Model 2)	PSHM taking into account the Tohoku earthquake (M9)	
■Setting conditions for the Tohoku EQ	
・Source area： Aftershock area
	・The origin of the time：2011/1/1
	・Average interval： 600 years
	・Latest activity period：
15th century
・Occurrence probability in 30 years：
15.4%
・Ground-motion equation：
Si and Midorikawa(1999)(Saturated with Mw8.3)

PSHMs considering the Tohoku type earthquake	(a) PSHM2011	
 (b) PSHM2011＋TohokuM9	

PSHMs for Earthquake CategoryⅠ	(a) PSHM2011	

(b) PSHM2011＋TohokuM9	

PSHMs for 2012	
Model 1	Model 2	Comparison of hazard curves	Black dashed curve：PSHM2011, Black curve：PSHM2011 with M9	
Blue line：PSHM2012(Model1), Red curve：PSHM2012(Model2)	

(a)

Fukushima 	

(d) Saitama(b) Mito	(e) Chiba		(c) Utsunomiya	(f) Tokyo	

Strong-motion maps considering
low-probability earthquakes
	
1,000 years	

10,000 years	

100,000 years	

Based on the averaged long-term seismic hazard assessment, evaluating strong-motion level for
10,000 ~100,000 years return period, we should prepare the maps that show the distribution ofstrong-motion level, which represent effect of major earthquakes on active faults andsubduction zone earthquakes with low-probability.
Regarding the seismic hazard assessment for low probability, at present, it is insufficient toevaluate the uncertainty for low probability M8 class earthquakes and it is necessary to improve
techniques for them.	

Japanese-Chinese-Korean cooperative joint researchcollaboration program	
Title of cooperative research project (2010-2013)
Seismic Hazard Assessment for the Next Generation Map
Research Leaders
Hiroyuki Fujiwara (Japan, NIED)Tao Xiaxin (China, Harbin Institute of Technology)
Myung-Soon Jun (Korea, KIGAM)

Cooperative joint research
1. To review the data and methodologies adopted in SHA
maps of the three countries, and re-evaluate and improve
the SHA in each of the countries.	
2. To compare the data and the methodologies with thestate of the art, and see if there anything could be accepted
for the next generation maps.	
3. To develop a procedure to establish ground motion
equations for maps.	
4. To combine the probabilistic seismic hazard assessment
and the scenario seismic approach, the latter is especiallyfor near field of potential large earthquake.

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DRI for Earthquakes	

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Companies, NPOs	
Disaster	……
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災害危険度メータ_ □×

自宅の登録 家族の登録 自宅の耐震評価 備蓄登録
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緊急地震速報なし
台風や豪雨予想

危険度３
大丈夫？

Disaster-Risk Management
System for Local Community

なし

DRMS forLC
DRMS for I
災害危険度メータ
自宅の登録 家族の登録 自宅の耐震評価
ファイル 編集 表示 ツール ヘルプ

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DRMS for I
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ファイル 編集 表示 ツール ヘルプ

危険度３
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_ □×
備蓄登録

緊急地震速報

緊急地震速報なし

なし

台風や豪雨予想

台風や豪雨予想

なし

危険度３
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なし

DRMS forLC

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