Earthquake Damage and Seismic Code for Buildings in Japan
Yuji Ishiyama, Dr. Eng.
Professor Emeritus, Hokkaido University, to-yuji@nifty.com

Summary
Major earthquakes that have forced to make development and modifications to seismic code
are shown. The current seismic code for buildings in Japan includes allowable stress calculation using linear analysis and ultimate lateral capacity calculation using nonlinear analysis. The code consists of six seismic design routes from 0 to 5 and each design route is asequence of some designated structural requirements among (a) to (j).

1 Introduction
Many big earthquakes have occurred in and around Japan since ancient times and have caused severe
damage, but the scientific research on seismology or earthquake engineering began only after the Meiji
Restoration in 1868. The Yokohama Earthquake occurred in 1880, and the Seismological Society ofJapan was established. Since then, every big earthquake forced to make some development in earthquake
resistant technology and seismic codes. The 1891 Nobi Earthquake led to the formation of the Earthquake
Investigation Committee, the 1923 Great Kanto Earthquake brought about the introduction of the seismic
coeﬃcient, the 1968 Tokachi-oki Earthquake prompted the revision of shear reinforcement of reinforced
concrete columns, the 1978 Miyagi-ken-oki Earthquake led to the adoption of a new seismic design
method, the 1995 Great Hanshin-Awaji Earthquake made the revision of shape factor and introductionof Seismic Retrofitting Promotion Law, and the 2011 Great East Japan Earthquake brought about a new
notification for tsunami evacuation buildings, etc.
This is to report the major earthquakes, development of seismic code and the current seismic code inJapan.

2 Major Earthquakes and Develpoment of Seismic Code
2.1 1880 Yokohama Earthquake and 1891 Nobi Earthquake
After the Meiji Restoration in 1868, the government of Japan abandoned the 230 year isolation from foreign countries and resumed overseas trade. The government invited many foreign researchers, scientists
and engineers to Japan in order to develop Japanese industries as well as to absorb Western culture assoon as possible. The Yokohama Earthquake (M=5.5) occurred in 1880 and caused moderate damage.
The earthquake was not very severe, but was strong enough to frighten resident researchers from overseas countries. In the same year, the Seismological Society of Japan was founded and scientific researchon seismology and earthquake engineering began.
The 1891 Nobi Earthquake (M=7.9, 7,273 deaths) caused very severe damage. In the following year
(1892), the Earthquake Investigation Committee was founded and research on seismology was accelerated. The Earthquake Investigation Committee was rechartered to the Earthquake Research Institute in1925 which now belongs to the University of Tokyo.

2.2 1923 Great Kanto Earthquake and Seismic Coeﬃcient
After the 1923 Great Kanto Earthquake (M=7.9, more than 105,000 deaths or missing), the provisionthat “the horizontal seismic coeﬃcient shall be at least 0.1” was added in 1924 to the Urban Building
Law which had been enforced since 1919.

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The seismic coeﬃcient was specified to be 0.1, because the seismic coeﬃcient of ground surface atTokyo was estimated to be 0.3 of the acceleration due to gravity during the Great Kanto Earthquake, andthe safety factor of material strength to allowable stress was assumed to be 3.

2.3 Building Standard Law after World War II
Since the enforcement of the Urban Building Law, one allowable stress had been specified for eachstructural material. After World War II, the Building Standard Law replaced the old regulations in 1950.
Then the concept of “permanent” (long term) and “temporary” (short term) was introduced to load combinations and allowable stresses. Since the temporary allowable stress became twice of the old allowablestress (equivalent to the permanent allowable stress), the horizontal seismic coeﬃcient became 0.2 whichis twice of the old regulations.

2.4 1968 Tokachi-oki Earthquake and Strengthening of Shear Reinforcement
In the 1968 Tokachi-oki Earthquake (M=7.9, 52 deaths), many reinforced concrete buildings suﬀered
severe damage which had been believed to have enough earthquake resistant capacity. The BuildingStandard Law was revised and shear reinforcement of reinforced concrete columns was strengthened.
Incidentally, the eﬀectiveness of this revision was proven in the 1995 Great Hanshin-Awaji Earthquake.

2.5 1978 Miyagi-ken-oki Earthquake and New Seismic Design Method
The fundamental revision of the seismic design method became necessary because of the development of
the earthquake response analysis technology and the damage caused by the 1968 Tokachi-oki Earthquakeand other earthquakes.
A five year national research project for establishing a new seismic design method was carried out
from 1972 to 1977 in Japan. The 1978 Miyagi-ken-oki Earthquake (M=7.4, 28 deaths), hit the Sendai
area and its occurrence accelerated the adoption of the new seismic design method. The new seismic
design method, which had been already proposed, was reviewed and evaluated for use as a practicaldesign method. The Building Standard Law was revised in 1980, and the new seismic design method has
been used since 1981.
The new seismic design method was developed introducing up-to-date knowledge of earthquake
engineering at that time. The major changes were (1) the introduction of two levels of earthquake motions(severe and moderate earthquake motions), (2) simple formulae to evaluate seismic shear forces and theirdistribution along the height of buildings with shorter natural period as well as longer natural period, (3)seismic shear coeﬃcient instead of seismic coeﬃcient, (4) consideration of structural balance in plan andin elevation (story drift and shape factor to consider stiﬀness and eccentricity), (5) structural characteristic
factor to consider strength and ductility, etc. The new seismic design method for buildings is now called
as “Allowable Stress and Lateral Shear Capacity Method” and it is summarized as Routes 1 , 2 and 3
in the next section.

2.6 1995 Great Hanshin-Awaji Earthquake and Seismic Diagnoses
Although the validity of the new seismic design method was proven during the 1995 Great HanshinAwaji Earthquake (M=7.2, 6,430 deaths), the Building Standard Law was revised in 1998. The revision
was to make minor amendments to the shape factor, and to introduce performance-based “Response andLimit Capacity Method”. This method is referred as Route 4 in the next section.

2.7 2011 Great East Japan Earthquake and Tsunami
The damage caused by the 2011 Great East Japan Earthquake (M=9.0, 19,000 deaths or missing) was
mainly due to huge tsunami. The Bulding Standard Law has not been revised yet, but a new notification
was issued for tsunami evacuation buildings.
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3 Current Seismic Code for Buildings
3.1 Structural Requirements
The buildings shall satisfy the designated structural requirements accoding to structural type, floor area,height, etc. as shown in Fig.1.
(a) Structural specifications shall be fulfilled for any buildings. (Some of them can be alleviated forRoute 3 , and most of them except for duarability can be alleviated for Routes 4 and 5 .)(b) Allowable stress calculation is to verify that the stress caused by the lateral seismic shear for moderate earthquake motions shall not exceed the allowable stress for temporary loads. (This is applied toRoutes 1 , 2 and 3 .)(c) Height, strength, etc. limitation (along with allowable stress calculation and structural specifications) is to realize seismic safety for small scale buildings. (This is applied to Route 1 .)(d) Story drift limitation is to prevent non-structural elements from earthquake damage. (This is applied
to Routes 2 , 3 and 4 .)(e) Stiﬀness and eccentricity limitation is to prevent earthquake damage concentration to a part ofbuildings. (This is applied to Route 2 .)(f) Strength and ductulity limitation is to give adequate strength and ductility against severe earthquake
motions. (This is applied to Route 2 .)(g) Ultimate lateral capacity limitation is to verify seismic performance against severe earthquake
motions, calculating ultimate lateral capacity of the building. (This is applied to Route 3 .)(h) Damage limit is to verify that the damage of the building shall be within the allowable level against
rare earthquake motions. (This is applied to Route 4 .)(i) Safety limit is to verify that the building may not collapse against very rare earthquake motions.
(This is applied to Route 4 .)A Small scale buildings
B Medium scalebuildings
C Large scale buildings=

height < 31m(a) Structural specifications(j) Time history response analysis is to verify the seismic safety of the building through time history
response analysis. (This is applied to Route 5 .)Route 0(b)
Allowable
stress(e) Stiffness, eccentricity(f) Strength, ductility
(d)
Story
drift

D Large scale buildings=

E High-rise buildings
height > 60m

End

Route 3(i) Safety limit

Route 4(j) Time history response analysis

Route 5=height < 60m

Route 2(g) Ultimate
lateral capacity

31m < height < 60m

A ～ D Buildings

Route 1(c) Height, strength(h)Damagelimit

Figure 1: Design routes for buildings3

3.2 Seismic Design Routes
Each sequence of some designated structural requirements among (a) to (j) forms a seismic design route,from 0 to 5 , as follows (see Fig.1).
Route 0 requires no structural calculation. The seismic safety is realized by (a) structural specifictions.
(This route is applied to small scale buildings.)
Route 1 requires (b) allowable stress calculation, and some limitations of (c) height, strength, etc. The
seismic safety is realized with the supplement of (a) structural specifications. (This route is applied tosmall and medium scale buildings.)
Route 2 requires (b) allowable stress calculation, and limitations of (d) story drift, (e) stiﬀness andeccentricity, and (f) strength and ductility. The seismic safety is realized with the supplement of (a)structural specifications. (This route is applied to buildings, whose height does not exceed 31 m.)
Route 3 requires (b) allowable stress calculation, (d) story drift limitation, and (g) ultimate lateralcapacity calculation. The seismic safety is realized with the supplement of (a) structural specifications(some of them can be alleviated). (This route is applied to buildings, whose height does not exceed
60 m.)
Route 4 requires verifications for (h) damage limit, (i) safety limit and (d) story drift limitation. The
seismic safety is realized with the supplement of (a) structural specifications that can be alleviated except
for durability. (This route is applied to buildings, whose height does not exceed 60 m.)
Route 5 requires (j) time history response analysis to verify the seismic safety, and (a) structural
specifications can be alleviated except for durability. (This route is applied to all buildings, including
whose height exceeds 60 m.)

3.3 Design Seismic Shears
For (b) allowable stress calculation and (g) ultimate capacity calculation, the seismic shear Qi of the i-thstory is calculated as follows (see Fig.2).
Qi = Ci Wi(1)where, Ci is the lateral seismic shear coeﬃcient of the i-th story that shall be determined as Eq.(2) and
Wi is the weight of the building above the i-th story.
wn

Pn

Q n = Cn wn

Pi : lateral seismic forceof the i-th story
Qi : lateral seismic shearof the i-th story
Ci : lateral seismic shear coeﬃcientof the i-th story
wi : weight of the i-th story

wi

Pi

n

Q i = Ci Σwi
i

P1

w1
n

Q 1 = C1 Σwi
1Figure 2: Lateral seismic force Pi and shear Qi of the i-th story4

C i = Z R t Ai C 0(2)

where, Z is the seismic hazard zoning factor (see Fig.3), Rt is the design spectral factor (see Table 1 andFig.4) which shall be determined according to the type of soil profile (see Table 2) and the fundamental
natural period T of the building, Ai is the lateral shear distribution factor (see Fig.5 a), and C0 is thestandard shear coeﬃcient that shall be as follows.
C0 >= 0.2 : for moderate earthquake motions
C0 >= 1.0 : for severe earthquake motions: A

Z = 1.0: B

Z = 0.9: C

Z = 0.8

Okinawa :Z = 0.7(3)

Figure 3: Seismic hazard zoning factor Z
Table 1: Design spectral factor* Rt
T

T < TcRt

1

Tc <= T < 2 Tc

T>
= 2 Tc1 − 0.2

1.6 T c
T

(T

Tc

)2
−1

* : Rt can also be calculated by other methods, but the calculated value
shall not be less than 0.75 of the value given by this table.
T : Fundamental natural period (s) of the building (see Fig.(6)).
T c : Critical period (s) of the soil (see Table 2).

The lateral shear distribution factor Ai is given as follows (see Fig.5 a).
( 1) 2T
Ai = 1 + √ − αi1 + 3Tαi(4)where, αi is the normalized weight of the i-th story, which is calculated as the weight above the i-th story
divided by the weight above the ground level as follows.
∑nWi
j=i w jαi = ∑ n(5)=W
j=1 w jwhere w j is the weignt of the j-th story.
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Table 2: Classification of soil
Soil Profile

Ground Characteristics

T c (s)Type 1(Hard soil)

Ground consisting of rock, hard sandy gravel, etc., classified as tertiary orolder, orGround whose period, estimated by calculation or by other investigation, is
equivalent to that of the above.

0.4

Other than Type 1 or 2.

0.6

Alluvium consisiting of soft delta deposits, topsoil, mud, or the like (including
fills, if any), whose depth is 30 m or more, land obtained by reclamation ofmarsh, muddy sea bottom, etc., where the depth of the reclaimed ground is 3 m
or more and where 30 years have not yet elapsed since the time of reclamation,or
Ground whose period, estimated by calculation or by other investigation, is
equivalent to that of the above.

0.8

Type 2(Medium soil)

Type 3(Soft soil)

Critical period T c is used in Table 1.
1

Soil profile type 3 (soft)
Soil profile type 2 (medium)

Rt

Soil profile type 1 (hard)

0.5

0

1

2

3

T (s)

Figure 4: Design spectral factor Rt
Qi / Q1

Ai
1

2

3

4

5

0

0

0.2

0.2

T=∞
0.6
0.8

0.4

0.6

0.8

1

0.4

0.4

αi

0.2

αi

T = 1.0
T = 0.2
T=0

0.6
0.8

1

T =∞
T = 1.0
T = 0.2
T=01b) Ai αi distributiona) Ai distribution

Figure 5: Lateral shear distribution factor Ai and its shear distribution Ai αi

The fundamental natural period of the building T (s) can be calculated as follows.
T = h (0.02 + 0.01λ)6(6)

where, h (m) is the height of the building, and λ is the ratio of the total height of stories of wooden or
steel construction to the height of the building.
The period can also be calculated by eigenvalue analysis considering the mass and stiﬀness of thebuilding. The value of Rt , however, can not be less than 0.75 of the value given by Table 1.

3.4 Story drift (Structural requirement (d) for Routes 2 , 3 and 4 )The drift of each story of the building (except the basement) caused by the lateral seismic shear for
moderate earthquake motions or by the lateral seismic force at damage limit shall not exceed 1/200 of
the story height. This value can be increased to 1/120, if the nonstructural elements shall have no severe
damage at the increased story drift limitation.

3.5 Lateral stiﬀness ratio (Structural requirement (e) for Route 2 )The lateral stiﬀness ratio Rs of each story (except the basement) shall be equal to or greater than 0.6.
rs
> 0.6
r¯s =

Rs =

(7)

where, rs is the lateral stiﬀness, which is defined as the story height divided by the story drift causedby the lateral seismic shear for moderate earthquake motions, and r¯s is the mean lateral stiﬀness that isdefined as the arithmetic mean of rs ’s (see Fig.6).
In case the lateral stiﬀness ratio Rs becomes less than 0.6, the ultimate lateral capacity (Route 3 )Feshall be calculated and satisfy Eq.(9).
P4 = Q 4

1.5
1

r S4

1.0

P3 =Q 3 - Q 4
1

r S3
P2 = Q 2 - Q 3
1

r S2
P1 = Q 1- Q 2

r̄s =
O

∑n

i=1 rsi
0.15
n

0.3

Re

0.6

Rs

rsi
> 0.6
Rs =
r̄s =
Fs
2.0

1

r S1

1.0

Figure 6: Lateral stiﬀness ratio Rs of the i-th storyOY

3.6 Stiﬀness eccentricity ratio (Structural requirement (e) for Route 2 )The stiﬀness eccentricity ratio Re of each story (except the basement) shall be equal to or less than 0.15.
Re =e< 0.15
re =

(8)
k yi

where, e is the eccentricity of the center of stiﬀness from the centerof mass, and re is the elastic radiusGthat is defined as the square root of the torsional stiﬀness divided
by the lateral stiﬀness (see Fig.7).
ey SSyIn case the stiﬀness eccentricity ratio Re becomes
more than e0.15,
the ultimate lateral capacity (Routexk xi
3 ) shall be calculated and satisfy Eq.(9). Yi

O

S x Xi

7

X

r S1

1.0

O

0.6

Rs

Y

k yi
G
Sy

ey

S
ex

k xi

Yi

O

S x Xi

G: center of mass
S: center of stiﬀness
Kxi , Kyi : lateral stiﬀness of element iin X and Y directions
∑(
)
∑(
)
Kyi XiKxi YiSx = ∑
Sy = ∑
Kyi
Kxi∑{ ()2 } ∑ { ()}
Kr =Kxi Yi − S y +Kyi Xi − S x 2
√
√
Kr
Kr
∑
rey = ∑
rex =
Kxi
Kyi
ey
ex
Rey =
Rex =
X
rex
rey

Figure 7: Stiﬀness eccentricity ratio Re in X and Y directions

3.7 Ultimate lateral capacity (Structural requirement (g) for Route 3 )The ultimate lateral capacity (lateral load bearing capacity) of each story (except the basement) shallbe equal to or greater than the specified lateral shear Qun determined as follows.
Qun = Ds Fes Qud(9)where, Qud is the lateral seismic shear for severe earthquake motions defined as Qi in Eq.(1) with Eq.(2)where C0 >= 1.0, Ds is the structural characteristic factor in Table 3, and Fes is the shape factor whichshall be determined as follows.
Fes = Fe Fs(10)where, Fe and Fs are given in Table 4 and Table 5, respectively (see Fig.8).
The ultimate lateral capacity can be calculated as the shear of the story when the buiding come toyield subjected to horizontal forces, using structural mechanics, e.g. method of virtual work. Recently
the lateral capacity Q is usually calculated using computer program of so-called “pushover analysis” (seeFig.9).
Table 3: Structural characteristic factor* Ds
Type of frame
Behavior of members(1) Ductile moment
frame
0.3

(2) Frame other thanlisted in (1) & (3)0.35(3) **

A

Members of excellent ductility

0.4

B

Members of good ductility

0.35

0.4

0.45

C

Members of fair ductility

0.4

0.45

0.5

D

0.45
0.5
0.55
Members of poor ductility* The values can be decreased by 0.05 for steel frame reinforced concrete or steel buildings.
** Frames with shear walls or braces for reinforced concrete and steel frame reinforced concrete buildings,
and frames with compressive braces for steel buildings.

3.8 Acceleration Response Spectra (Structural requirements (h), (i), (j) for Routes 4 ,5 )The acceleration response specra are used for Route 4 (Response and limit capacity method) and Route
5 (Time history response analysis).
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Table 4: Shape factor Fe and stiﬀness eccentricity ratio Re
Re of Eq.(8)Re <= 0.150.15 < Re < 0.3
0.3 <
= Re

Fe

Fe
1.0
linear interpolation
1.5

P4 = Q 4

Table 5: Shape factor Fs and1.5lateral stiﬀness ratio Rs
1

Rs of Eq.(7)P3 =Q 3 - Q 4
Rs >
= 0.6
0.6 > Rs

1.0

r4

1

r3

O

r2

Fs

P3

P2 = Q 2 - Q 3
1

P2

Fe

P1 = Q 1- Q 2

4

r4

0.3

Re

0.6

Rs

1

1.5
1

0.15

2.0

P1

= Q4

Fs
1.0
2.0 − Rs /0.6

r1

1.0

1.0

=Q 3 - Q 4
1

r3

O

r2

Fs

= Q 2 - Q3
1

Q 1- Q 2

0.15

0.3

O

Re

FigureY8: Shape factor Fes = Fe Fs

2.0

P13

Q1 = P1 + P2 + P3

r1
B

1.0

P2

A

Q

O

C

Q2 = P2 + P3

0.6

Rs

Sy

P1
Y

×D

Kyi

G
Q3 = P3
ey S
ex

Yi

×
Kxi

×

O〜A : linear-elastic
range
A〜B : formation ofplastic hinges
B〜C : formation ofcollapse mechanizm
D : collapse

O

O

Δ

a) Pushover analysis
Kyi

S x XiXb) Lateral capacity Q

Figure 9: Pushover analysis and lateral capacity Q

G
Sy

ey

S
ex

Kxi
SAd (m/s2 ) is the acceleration
response at damage limit on the engineering bedrock that is given as
follows (see Fig.10).
(0.64 + 6 Td ) for Td < 0.16


X

O
S x Xi(11)
SAd = 1.6
for 0.16 <= Td < 0.64




+
P
+
P
1.024/Td Q1 = P
1
2
3<
for 0.64×= Td
BC
where, Td (s) is the response period of the building at damage limit.
2 = Plimit
2 + Pon3 the engineering bedrock that is given asSAs (m/s2 ) is the acceleration response at Q
safety×Afollows (see Fig.10).

Q
(3.2 + 30QTs )= P
for Ts < 0.16


3
3


×
SAs = (12)
8.0
for 0.16 <= Ts < 0.64

5.12/Ts
for 0.64 <
= Ts

Yi

○

○

9

O

Δ

0
0

1

2

3

Acceleration response, S Ad & SAs
2
Acceleration response(m/s2)S Ad or S As (m/s )Natural period, T (s)

9
8
7
6

SAs = 5SAd

5

SAd

4
3
2
1
0
0

1

2

3

NaturalPeriodperiod,
Td or TsT(s)d & T s (s)Figure 10: Acceleration response spectra at damage and safety limits

where, Ts (s) is the response period of the building at safety limit.
The earthquake motions at the ground level, for time history response analysis, shall conform to
the designated response spectra, that shall be estimated, using the product of the acceleration responseat engineering bedrock and the seismic hazard zoning factor Z, and considering the amplification ofearthquake motions through surface soil above the engineering bedrock.

4 Conclusions
Major earthquakes, development of sesimic code and the current seismic code for buildings in Japan havebeen summarized. It can be seen that the earthquake damage forced to make modifications to seismiccode. Recent major earthquakes have shown that it is important to improve seismic capacity not only forstructural members but also for non-structural components as well. Furthermore, recent huge tsunami
damage causes other serious problems to be solved.

Reference
Yuji Ishiyama: Introduction to Earthquake Engineering and Seismic Codes in the World, July 2012,
http://iisee.kenken.go.jp/

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