10iwsmrr, Sep. 25, 2013

Site specific ground motion characteristics
and building damage in Sendai area during
the 2011 Tohoku earthquake

Masato Motosaka

Contents (I)Strong motion observation sites in Sendai area andGeological structure
Ground Motion Characteristics in Sendai Area during
2011 Tohoku earthquake
Distribution of PGA,PGV, and spectra
Comparison of 1978 Eq. at same obs. Pt.
Site specific ground motion amplification andbuilding damage- Oroshimachi on alluvial deposit- Nagamachi on alluvial deposit + deep structure- Aobayama hill

2- 1Contents(II)Specific building damage
Pile foundation building
Non-structural elements*especially ceiling board drop
Housing land failure
Impact of geological structure on non-linear
response of building structures
Conclusions
Lessons from the Tohoku Earthquake focused on
ground motion and building damage

Necessity of ‘holistic’ earthquake counter measures

Location of strong motion
observation sites
Fault
JMA/MYG/
NIED
DCRC
Small Titan
SVA
JR,NEXCO

2- 2

Surface geology andobs. pts. of ＤＣＲＣ,Tohoku Univ.
Fault
DCRC
Small Titan
SVA
JMA, NIEDSendaiStation仙台駅
東北新幹線
Shinkansen
R286

Sumitomo
Aobayama

Oroshimachi
0m

Nagamachi-75m

Deep Underground Structurein Sendai Area
Dominant period

Bedrock depth

2- 3

PGA and PGV distribution

7

PGA & PGV of Observation data
～ DCRC, Tohoku University networkMax.
Acc.(PGA)
300cm/s/s～800cm/s/s
Max.
Vel.(PGV)
30cm/s～80cm/s（Ohno andMotosaka, 2011）

2- 4

Acceleration waveform（NS-comp.)
Pref. Lib.
Shogen E.S.

North-west

MatsumoriE.S.
1st J.H.S.
THU (Aobayama)
Sumitomo
Nishitaga J.H.S.

N-R fault

Tomizawa J.H.SNagamachi C.C.
Furujiro J.H.S
Minamikoizumi E.S.
Oroshimachi

South-East

Okino E.S.

Spectral distribution inSendai City
Sendai station (blue)is hard to shake (EngineeringbedrockWest-north of the fault: short period dominance due tosurface geology
East-south of the fault: 3s period content dominance due
to deep underground structure）
North-west

South-East

2- 5Spectral distribution due to the 2011
Tohoku earthquake (Mw9.0）
0.2s

1s

3.2s

NSEW

11

Amplitude dependent dominantperiodPeak due to deepunderground structure(period:3s)
Amplitude dependent
dominant period peak due
to surface geology(period: 0.5-1.0s)

No.025（Nagamachi）

2- 6

Observed waveforms compared to １９７８
＆2005 Miyagi-ken Oki earthquakes at
Sumitomo Building (near Sendai Station)
Earthquake
Earthquake

EW-compNS-comp.
NSdirection EW
direction
Type ofUD
direction SeismometerUD-comp.
S25E
S65W
Seismometeryr/m/dyr/m/dＭ
Magnitude

2011/3/11

9.0

317.7

234.1

160.3

SSA-1

1978/6/12

7.4

250.9

240.9

90.8

SMAC-Q

2005/8/16

7.2

120.8

78.0

56.4

SSA-1Long duration（about 3 minutes）
Ground shaking of 2st wave group is almost the same spectral
characteristics as 1978 eq.

unit：cm/s/s

200cm/s/s
200cm/s/s
2011 Off Pacific(M9Pacific(M9.0)
1978 MiyagiMiyagi-ken Oki(M7Oki(M7.4)
2005 MiyagiMiyagi-ken Oki(M7Oki(M7.2)
050

100

Spectral characteristics
Period contents less than
1.5s are larger thanthose of 1978 eq. 1s
period contents are 20%
larger, around 0.5s
contents are 2 times
larger.
Period content around 3s
is two times larger
compared to 1978 eq.
Shorter period contentsthan 1.5s is lager in theNS comp. and Longerperiod than 1.5s is lagerin EW comp.

NSEW（Motosaka, Ohono & Mitsuji, 2011)

2- 7

150 time（time（sec）sec）

Difference of spectral
amplification due to soil
conditions

1s period content is
4 times amplified inNagamachi
Short period
contents are
more than
two times
amplified inOroshimachi

3s long period
content is amplified
more than twotimes

Different Ground Motion Characteristics at
Sendai Station (Diluvium) and Damage ofOld building on Alluvium site
Sa-Sd Spectra

OroshimachiSendai Station

2- 88 and 9 story buildings’ damage due toresonance to the amplified ground motion
at around 1s period content
Aobayama hill

100m-120m

Neo Tertiary Layers

Sendai st.

1978 Miyagi-ken
Oki
Velocity(cm/s)

Velocity(cm/s)

2011 Tohoku

2 times
amplification

Period (sec)

2 times
amplification

Period (sec)

Different spectral amplification for the twophases and resonance of 9-story building at
Aobayama hill (NS direction)

Amplification is two times in the 2nd phase, but not amplified
in the 1st phase.

2- 9Damage to 9 story SRC building at Aobayama
campus, Tohoku Univ. (THU Building)Research Building of Department of C.E & A-B.S Eng.

1969 Completion
1978 Earthquake
2000 retrofit
2005 Earthquake
2008 Earthquake
Ground motion ataround 1s period
content is amplified
two times

Strong motion records
shows：Max Acc. of NS-comp.
1F: 333cm/s/s
9F: 908cm/s/s

４ corner external columns aredamaged heavily at their bottom

Earthquake Observations at THU Building

1F

SMAC-MD
5FMicroSMA

9F

Observed Acc. Waveforms(SMAC(SMAC-MD)

Location of Seismometersin plan and section

2 - 10Reproduction of the shaking at 9th fl.
by 3D shaking table

Investigation of dynamic behavior～Occurrence of Partial uplifting

Explanation of partial uplifting(from NHK-Special MEGAQUAKE III)

Confirmation of higher
harmonics by wavelet analysis

2 - 11

System identification of time dependent
dynamic characteristics using Kalman Filter（TR direction）
Phase A
Phase B
Relative disp.

Damping
Damping factor is increasing
Damping factor is large in small amplitudewith amplitude
and small in large amplitude
Natural freq.

Natural frequency is decreasing withincrease of amplitude

Research building for Department ofInformation and Intelligent Systems
8-story SRC building
Damage of Pent House

Damage of experimentalequipments

Drop of elevator cargo

Damage of research building and equipments,
but no injured person! Drop of elevator!
Earthquake Early Warning! + property of shaking?

2 - 12

Specific Building Damage
Pile foundation damage
Ceiling board drop damage
Housing land damage

Damage of pile-foundation building
condominium building in Takasago
Inclination angle:1/56
Inclination angle:1/100

Inclined 14 story SRC building
Completion: 1976
Damaged building during 1978 eq.
Pile length: 24m

2 - 13

Increased to 1/45
due to after shockMeasurement of subsidence of thedamaged building
13.23

13.48 1
2N4
13.28

13.59
35

13.54 6
13.55

13.26
13.54

78

9
10

11

13.55
13.48

13.57

The Reinforced Building was notdamaged even if severe shaking（Sa-Sd Spectra））

Reinforcement offoundation

Ground Motion characteristics inNagamachi
Reinforcement leads to no structural damage against verystrong ground motion with 1s period content！

2 - 14

Inclined RC building in OroshimachiDamage of piles

Construction year: 1983
Pile length:26m

Fall of suspension type ceiling boardof large span building

Multi-purpose hall in Sendai
Suspension type ceiling board;
60% during main shock and theremaining 40% during aftershock

Hall of Taihaku-ku Culture
Center, Sendai

2 - 15

Microtremor measurement at thebuilding with ceiling board damage-3

Ave. Spectral Vel. Amp. (cm)2.0x10

Roof center屋根中央ofEW
the hallNS

1.5

UD

1.0

0.5

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Frequency(Hz)＊ Vertical motion is largely induced.
＊ Building stiffness is relatively high and is escaped fromresonance to 1s period content

Damage of Housing Lands in Sendai City（5,000 points at ９ housing lands)
Housing land damage in Sendai City

Common points:
Valley-filledhousing landHigh water level
Long-duration
ground motion

2 - 16

Housing damage by filled soil failure

Nishi-Seikaen,
NishiSeikaen, AobaAoba-ku,ku, Sendai

Oritate,Oritate, AobaAoba-ku,
ku, Sendai

Impact of geological structure on
non-linear response of building structures
Building model

Non-linear SDOF system

Objective 4 sites
Objective buildings: 6-, 9-,15-, and 20story standard RC building with 3.4m
story height
Fundamental period T1(s)T1=0.02H H：Building height(m)Ky=0.3K
Fc=1/3 Fy

Num. Story

1st period(s)

6915
20

0.41
0.61
1.02
1.36

Hysteresis model: Takeda model2 - 17

Pseudo Velocity (NS-component)
pSv Response(cm/s)

350

Nagamachi

h=0.05300

Oroshimachi

250

Aobayama
Sumitomo

200

Design Spectra

150
100
50
00.1

1.010.0Period(sec)At around 1s period content, Nagamachi site is amplified by 4times compared to Sendai station (Sumitomo), Aobayama site is 2times, and Oroshimachi site is 1.8 times.

Strength Demand Spectra
1.4

6-storyh=0.03

Oroshimachi

2.0µ=1.009-story1.5µ=1.80µ=4.001.0

15-storyµ=6.0020-story

0.5
0.0
0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

h=0.03µ=1.00µ=1.80µ=4.00µ=6.000.8

15-story

0.6
0.4

20-story

0.2
0.0

2.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

6-storyh=0.03µ=1.00µ=1.80µ=4.00µ=6.009-story

1.5
1.0

15-story 20-story

0.5
0.0

Base Shear Coef.

1.2

Nagamachi

2.5

1.8

2.0

Initial period (S)3.0

Base Shear Coef.

Aobayama

6-story

1.0

Initial period (S)2.0

9-story

1.2

Base Shear Coef.

Base Shear Coef.

2.5

Sendai Station (Sumitomo)

1.0

6-storyµ=1.00µ=1.80µ=4.00µ=6.000.8

9-story

0.6

15-story0.4

h=0.0320-story

0.2
0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.00.20.4

0.6

0.8

1.0

1.2

1.4

Initial period (S)Initial period (S)2 - 18

1.6

1.8

2.0

Necessary base-shear demand at Nagamachi,Aobayama, and Oroshimachi compared to Sendai
Station (Engineering bedrock)
μ＝1.0
6-story
9-story
15-story
20-story

μ＝1.86-story
9-story
15-story
20-story

Sendai
Nagamachi Aobayama
StationOroshimachi

1.0
1.0
1.0
1.0

3.0
1.6
1.4
1.6

2.1
2.4
1.8
2.0

1.3
2.4
2.0
1.1

Sendai
Nagamachi Aobayama
StationOroshimachi

1.0
1.0
1.0
1.0

2.3
1.4
1.5
1.8

3.0
0.8
1.4
2.9

1.5
0.9
1.2
1.5

μ＝4.0
6-story
9-story
15-story
20-story

μ＝6.0
6-story
9-story
15-story
20-story

Sendai
Nagamachi Aobayama
StationOroshimachi

1.0
1.0
1.0
1.0

2.9
2.3
1.3
1.0

1.7
1.6
1.4
1.5

1.9
1.6
1.0
1.3

Sendai
Nagamachi Aobayama
StationOroshimachi

1.0
1.0
1.0
1.0

2.6
2.0
1.0
1.2

1.3
1.6
1.5
1.7

1.4
1.5
1.0
1.4

About 3 times differences for 6 to 9-story buildings andAbout 2 times differences for 15 to 20-story buildings

Concluding Remarks
Due to progress of Seismic Building Code and seismic
retrofit promotion, amount of structural damage of building
structures was decreased
Remarkable damage difference due to soil conditions* Retrofit building on the hill was severely damaged* Necessity of appropriate seismic microzoning
Relation of observed high-acceleration records andstructural damage* appropriate ground motion index for structural damage
Effect of number of displacement cycles due to groundmotions of main shock with long-duration and many aftershocks

2 - 19Concluding Remarks (continued)
Effect of non-stationary ground motion comprisingmulti-phases on non-linear structural response* Moving resonanceAppropriate remaining seismic resistant capacity of thedamaged building due to past earthquake* Necessity of damage inspection for pile- foundation building
Effectiveness of reinforced part but the surrounding
remaining part
Well balanced seismic design* foundation and super-structure* Structural element and non-structural elements,
equipments

Necessity of holistic and well-balanced
earthquake counter measures
Necessity of holistic earthquake counter measuresin recent too much sectionalized society！
Collaboration beyond each academic field・・・Synergic combination
Local governments’ collaboration, international
collaboration・・・’cooperation and collaboration’‘Father of disaster prevention’‘Contemporary Leonardo da Vinci’

Dr. Torahiko Terada(1878-1935)

Essay ‘Tensai to Kokubou (Natural disaster and nationaldefense) ‘(1934)
Evolution of human society=differentiation
Destruction of one small portion may cause the wholedestruction
Lower animals have ability to regenerate!

2 - 20