Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanLESSONS OF THE 2011 GREAT EAST JAPAN
EARTHQUAKE FOCUSED ON CHARACTERISTICS
OF GROUND MOTIONS AND BUILDING DAMAGE
Masato Motosaka1
1

Disaster Control Research Center, Graduate School of Engineering,Tohoku University, Sendai, Japan, motosaka@ archi.tohoku.ac.jp

ABSTRACT: This paper starts from overview of ground motion characteristics, theobserved high acceleration records are discussed together with many long-duration
records as specific features. Then, ground motion characteristics during the 2011
earthquake are compared to those during the 1978 Miyagi-ken Oki earthquake. The site
amplification characteristics are also discussed based on the authors’ network in Sendai
in relation to 8- and 9 story buildings’ damage of Tohoku University. Pile foundation
damage and ceiling board damage are also introduced as specific building damage.
Key Words: Great East Japan earthquake, ground motion characteristics, site specificamplification, building damage, vibration characteristics,

INTRODUCTION
A major earthquake occurred in the Pacific Ocean off the coast of Miyagi, Japan on March 11,2011 and caused huge human and physical damage. The moment magnitude of 9.0 is the largest
recorded in Japan since modern seismograms became available. The fault plane has dimension with
450km by 200km (Fig.1). The earthquake caused many aftershocks. During three months after themain shock 500 aftershocks with magnitudes more than 5 were occurred. Some induced earthquakes
with magnitudes 6 to 7 class were also generated.
Although the most significant aspect of the 2011 Tohoku earthquake is the large Tsunami that
attacked the Pacific coast of Japan and claimed about 20,000 lives mainly by tsunamis together withhuge amount of physical damage, the earthquake caused structural damage by also severe groundmotion with long duration. Most of all the damaged buildings were designed by the old building codeand damaged by lack of seismic strength, short column shear failure due to sauce wall and a breast
wall, eccentricity of structural elements. Buildings with appropriate seismic reinforcement/retrofit
were mostly escaped from damage, which indicates effectiveness of the seismic reinforcement/retrofit.
But the structural damage caused by ground motion amplification was recognized. 8- and 9-story
buildings at Aobayama campus of Tohoku University were damaged due to ground motion
amplification in the site. Many pile foundation building were damaged during the earthquake. As
damage of non-structural elements, the tremendous number of ceiling board dropped during the main

166

shock and the major aftershock. Some of them caused killed persons for the first time.
In this paper, the author starts from overview of observed ground motion characteristics during
the earthquake, then investigates the observed high acceleration records with PGA of 2,700 cm/s/s andthe corresponding JMA seismic intensity 7 (instrumental intensity: 6.6) at the K-NET Tsukidate station.
Structural damage was quite light in the surrounding area are discussed together with many
long-duration records as specific features.
Then, ground motion characteristics during the 2011 earthquake are compared to those during the1978 Miyagi-ken Oki earthquake (M7.4) at the same observation site, basement floor of Sumitomobuilding near Sendai station, which is recognized as engineering bedrock motion. Site specific groundmotion amplification in Sendai area is also addressed based on strong motion networks including theauthors’ DCRC network. Difference of ground motion due to geological conditions is discussed.
Regarding specific building damage of 8- and 9-story buildings at Aobayama campus of Tohoku
University, ground motion amplification in the site was discussed based on the observation records at a
9 story SRC building of Departments of Civil Engineering and Architecture (THU building). Dynamic
behavior of the damaged THU building due to the amplified ground motion is also discussed together
with long-term monitoring of amplitude dependent dynamic characteristics of the building. As specificbuilding damage, the two pile foundation buildings which were damaged during the 1978 earthquake
comparatively discussed. An example of the pile foundation damage of the building constructed after
the New Seismic Design Code in 1981 is addressed. As damage of non-structural elements, someexamples of ceiling board drop damage are introduced. Finally, the author address the learning andlessons from the 2011 earthquake for stronger earthquake countermeasures of urban and building
structures.

JMA
Seismic
Intensity

Fig.1Slip distribution on the fault plane Fig. 2 Instrumental JMA Seismic Intensity and Observed(after NIED)
acceleration waveforms at K-NET stations

167

OBSERVED GROUND MOTION CHRACTERISTICS
Overview
Fig. 2 shows the observed acceleration waveforms in the Tohoku and Kanto regions. In Tohoku
region, the characteristic two phases are recognized but in Kanto including Tokyo the only one bigphase. Table 1 shows a list of large amplitude observation records in order of JMA seismic intensity,
instrument intensity (AIJ, 2011). The large intensity stations are concentrated in Miyagi prefecture,especially in the cities of Kurihara, Sendai and Ohsaki. As for the records in Sendai, detailed
information is described in section 3.
Table 1 List of large amplitude observation records

At the K-NET Tsukidate (MYG004) station, quite high acceleration records with PGA of 2,700
cm/s/s in NS component and 1880 cm/s/s in UD component were observed. The corresponding JMA
seismic intensity 7 (instrumental intensity: 6.6). At the time around 100s, NS and UD components
have especially large amplitudes. It is noted that structural damage was quite light in the surroundingarea. The authors investigated the high acceleration records and indicated unfavorable behavior withpartial uplifting and slipping of the foundation of the seismometer was recognized based on the
non-stationary spectral analysis and particle orbit analysis as shown later (Motosaka and Tsamba,
2011).
Fig. 3 shows 5%-damped pseudo velocity
response spectra for the major stations in Table 1,
together with spectra of Takatori record at the
1/17/1995 Kobe earthquake and Kawaguchi-machi
record at the 10/23/2004 Mid Niigata Prefectureearthquake as representatives of the earthquake
records in the heavily damaged zone by the pastdisastrous earthquakes.
Spectra of Takatori and Kawaguchi-machi
records are predominant around 1-2 seconds, while
spectrum amplitude at MYG004 (Terrace) is large
at the shorter periods but the 1-2s amplitude issmaller. On the other hand, MYG006 (Ohsaki
plain) and MYG013 (Sendai plain) have larger
1-2s amplitude compared with MYG004, and 4B9at the center of Furukawa (Ohsaki plain) haveFig.3 Pseudo velocity spectra at observation
similar amplitude level to that of Takatori. Spectral
characteristics of MYG004 and MYG006 are stations with larger seismic intensity in Tohoku
earthquake and past damaged earthquakes
discussed next.

168

Investigation of High Acceleration Records at K-NET Tsukidate Station
The K-NET Tsukidate station (MYG004) is located at the south of parking lot of Kurihara
Culture Hall. Observation hut is on a cliff with the EW directionality and height of 3m. The
configuration of the observation site including the hut with foundation is shown in Fig.4. The
foundation of the seismometer is concrete mass with dimension of 80cm x 80cm and the height of100cm. Fig.5 shows the observed acceleration waveforms of the 3 components during the March 11,
Tohoku earthquake. The horizontal PGA in the NS component is 2,700 gal and that in the EW
component is 1,269. Findings from the waveform characteristics of the observation records at K-NET
Tsukidate station are as follows.
1) The waveforms comprise two distinctive phases and the second phase has larger amplitude.
2) The acceleration values are large in the NS and UD components showing pulse-like waveform at
the time of 95 seconds in Fig.5
3) The dominance of NS component is consistent with the general property of the normal
direction’s dominance to the cliff, which suggests the topography effectFig.4 Configuration of observation site and sectionof seismometer’s foundation (after NIED)

Fig.5 Strong motion records at K-NET
Tsukidate station during the 2011 Tohoku
earthquake

Fig.6 shows acceleration waveforms and the corresponding wavelet basis non-stationary spectraof NS- and UD-components for 3 seconds (from 94s to 97s) at around the time of peak acceleration
generation showing in Fig.5. In the wavelet analysis, complex continuous Morlet wavelet is adopted as
mother wavelet. Fig.7 shows Fourier amplitude spectra for the same time section. Findings from those
figures are as follows.
1) For the dominant frequency of 4.2Hz in the horizontal (NS) component, odd number higher
harmonics are induced at around 12.6Hz (3 times) and 21.0Hz (5 times).
2) Vertical motion with even number higher harmonics is induced at around 8.4Hz (2 times) andaround 16.8 Hz (4 times).
These characteristics are consistent with the higher harmonic motion due to partial uplifting of thefoundation (Motosaka and Nagano, 1994).
Fig.8 shows acceleration orbit of NS-UD plane in the time section for 3 seconds from 94s to -97s.
Non-symmetric behavior is clearly shown. The particle orbit suggests unfavorable behavior withpartial uplifting and slipping of the foundation of the seismometer.

169

(a) NS component(b) UD component

Fig.6 Acceleration waveforms for 3 seconds at around the peak value generation time
and the corresponding wavelet basis non-stationary spectra(a) NS component
Fig.7(b) UD component

Fourier amplitude spectra for 3 seconds at around the peak value generation time

Fig.8

Acceleration Particle Orbit of NS–UD plane

Comparison of Response Spectra for Past Earthquakes at K-NET Stations
Fig.9 and Fig. 10 show acceleration-displacement response spectra (Sa-Sd spectra) in the larger
amplitude horizontal direction at MYG004 and MYG006. In these figures, the spectra due to the
7/4/2011 after shock and 14/6/2008 Iwate-Miyagi Nairiku earthquake are shown for comparison. It isfound form these figures that the observed motion at Tsukidate with JMA seismic intensity 7 isconsisted of shorter period contents than 0.3 sec and the displacement at around 1 sec is small as 10cm
even if the amount is larger compared to that for the 2008 earthquake.
In the case of K-NET Furukawa, it is found that the displacement during the 2011 earthquake was170larger compared to the 2008 earthquake by comparing the displacement spectral values for the twoearthquake and that the response displacement in the period range shorter than 1sec due to aftershock
on April 7 is almost the same as that due to main shock. These ground motion characteristics at
Tsukidate of Kurihara city and Furukawa of Osaki city are consistent with damage features in the twoareas.

Fig.9 Sa-Sd spectra for the earthquake
records at MYG004

Fig.10 Sa-Sd spectra for the earthquake
records at MYG006

Investigation of Long Duration Records
During the huge earthquake with long duration, building structures were shaken by many numbersof displacement cycles. It has been reported that many lead damper devices were damaged. In Ohsaki
city, Miyagi prefecture, a base-isolated building with lead damper device was damaged.
Fig. 11 shows observed acceleration waveform in EW component at K-NET Furukawa station(MYG006) and its displacement response spectra. The dominant period at around 4s is due tosedimentary basin. Fig.12 shows relation between the numbers of displacement cycles and threshold

Fig.11 Observation Record at K-NET Furukawa(EW-comp) and its displacement response spectra

171

Fig.12 Number of displacement cycles foreach period

displacement for various period of SDOF system with 10% damping. Note that the SDOF system with4s was shaken 3 times with displacement level of 40 cm and about 15 times with displacement level of
20 cm. Fig. 13 shows accumulated displacement for various period of SDOF system. The accumulated
displacement of 4s system exceed 20m and that of 3s system and 5s system reach 17m.
Fig.14 shows comparison of the accumulated displacement for different site for the Tohoku
earthquake and the past major earthquake records. For the same Tohoku earthquake, the value of
Sumitomo site near Sendai station is 5.9m for 3s, and Aobayama site is 7.8m for 3s. The value of
Takatori site for Kobe earthquake indicates 5.5m for 4s, and Kawaguchi-machi for the
Niigata-Chuetsu earthquake shows 3.3m for 4s. At the same K-NET Furukawa station, the value forthe 2008 Iwate-Miyagi earthquake is 13m for 4 s.
The information on numbers of displacement cycles and the accumulated displacement would bevery important for discussing the damage of base-isolation devices, structural and non-structuralelement of building structures.

Fig.13 Accumulated displacement for eachperiodFig.14 Comparison of accumulated displacement
for past major earthquake records

SITE SPECIFIC GROUND MOTION CHARACTERISTICS IN SENDAI AREA
Observation network and geological condition
The author’s Disaster Control Research Center (DCRC), Tohoku University, has strong motion
network in Sendai City and valuable observation records were obtained during the Tohoku
earthquake (Ohno and Motosaka, 2011). Seismometers are installed at ground floor (some are also at
top floor) of public buildings (Ohno et. al, 2004). Site locations and geological information are
shown in Fig. 15.
DCRC strong motion network observed not only 2011/3/11 main shock (9.0), but also 2011/3/09(M7.3) foreshock and 2011/4/07(M7.1) after shock. Table 2 shows outline of the observed records forthese earthquake events. During the main shock, the observation records were obtained at 14 stations.
The range of PGA values is from 300cm/s/s to 840cm/s/s and that of PGV values is from 30cm/s to
80cm/s. PGA values were large at north part of Sendai city where the soft surface layers deposit on
the hard rock. In these sites, dominant period of the ground motion is 0.4s to 0.7s.
Fig.16 shows pseudo velocity response spectra at east and west sides of Nagamachi-Rifu fault.
The spectrum at No.27, locating near Sendai station, is commonly plotted in each sides as a reference.
Spectra at west sides are equal to or relatively larger at short period (less than 1 second) than the
No.27 spectrum, while the spectra at east sides are significantly larger than the No.27 spectrum,
especially around 1 and 3 seconds. Such spatial difference may be due to the difference of geologicalstructure: west side of the fault is terrace and east side is lowland (alluvial deposits) in Sendai.

172

FaultDCRC
Small Titan
SVA
JMA, NIED(a)(b)
Sumitomo
Aobayama

Oroshimachi

Sendai
Station
仙台駅
東 北 新幹 線
Shinkansen
R286

Nagamachi

0m

(c)

-75m

Fig.15 Site locations of DCRC strong-motion network and surface geological information.
(a) Obs. Site (b) surface topography (c) Quaternary layer bottom
Table 2 Outline of earthquake records by DCRC strong-motion network, Tohoku University173

Fig.16 Comparison of pseudo velocity response spectra of DCRC strong-motion network
Fig.17 shows pseudo velocity response spectra (damping 5%) at Oroshimachi (No.23),
Nagamachi (No.25) compared to Sumitomo Building near Sendai Station (No.27). The safety limit
design spectrum is also shown in this figure. It is found that the period contents less than 1s areamplified by 3 times in Orishimachi, and that 1s period content at Nagamachi is 4 times amplified in
NS direction compared to Sumitomo site and shows the very large response value of 300cm/s. But in
EW direction the spectral amplification of 1s period content is not significant compared to NS
direction. It is also noted that 3s period content is dominant at Nagamachi and amplified by 3 times in
NS direction. This is effect of deep underground structure. Ground motion amplification
characteristics in Aobayama are discussed in the later section.

Fig.17 Comparison of velocity response spectra due to different soil conditions
Comparison of strong-motion characteristics between the 2011 and the past disastrous
earthquake records at the same stations
The observation records at Sumitomo building near Sendai station by DCRC, Tohoku University,
are very valuable to compare the records during the 1978 Miyagi-ken Oki earthquake at the sameobservation point. It is noted that the observation record was situated as engineering bedrock motion.
The observed ground motions at this observation point during the 2011 earthquake are compared with174

those due to 1978 Miyagi-ken Oki earthquake and also 2005 Miyagi-ken Oki earthquake.
Fig.18 shows the acceleration waveforms of horizontal two directions for 2011 Tohoku
earthquake (M9.0), 1978 Miyagi-ken Oki earthquake (M7.4), and 2005 Miyagi-ken Oki earthquake(M7.2). In this figure, the maximum acceleration values are shown for the three earthquakes. Fig.19
shows the corresponding pseudo velocity spectra. Findings focused on the comparison of the 1978
earthquake from these figures are as follows.
1) The envelope shape of the 1978 earthquake is almost same as the first phase of the 2011
earthquake.
2) Period contents shorter than 1.5s of the 2011 earthquake is larger than those of 1978 earthquake,about 20% larger at 1s, and twice as large at 0.5s
3) The period contents around 3s of the 2011 earthquake is more than two times as large compared tothose of 1978 earthquake.

(a) NS component(b) EW component
Fig.18 Comparison of observed acceleration waveforms for 2011 Tohoku earthquake andtwo Miyagi-ken Oki earthquakes(b) EW component(a) NS component
Fig.19 Comparison of observed acceleration waveforms for 2011 Tohoku earthquake andtwo Miyagi-ken Oki earthquakes
Site Specific Ground motion amplification in Aobayama hill and Resonance to Damaged
Building
It is important to investigate the ground motion characteristics at Aobayama campus of Tohoku
University where some 8- and 9-story buildings were severely damaged. Ground motion amplificationcompared to Sumitomo building was investigated for the 2011 earthquake and 1978 Miyagi-ken Oki
earthquake. One of the damaged buildings is a 9-story building of Departments of Civil Engineeringand Architecture, Faculty of Engineering, Tohoku University (THU Building). The building damage

175

feature and the related dynamic behavior are described later.
Fig.20 shows acceleration waveforms in the NS direction (Transverse direction) at 1st floor andtop (9th) floor of THU building for the 2011 earthquake and the 1978 Miyagi-ken Oki earthquake.
Fig.21 shows the site specific ground motion spectral amplification in Aobayama for the twoearthquakes, the 2001 Tohoku and the 1978 Miyagi-kun Oki earthquakes. Fig.22 shows the spectral
amplification in the THU building for the two earthquakes. It is noted that the amplification
characteristics of the 1st phase (phase A) and the 2nd phase (phase B) are different. In NS direction, thesecond phase is amplified by more than two times at around 1s period content at Aobayama campus
compared to Sumitomo building near Sendai station. The amplification characteristics are almost thesame as those of the 1978 Miyagi-ken Oki earthquake and the THU building was strongly amplified
by resonance.

Fig.20 Comparison of acceleration records at 1st floor (left) and 9th floor (right)

Fig.21 Site specific ground motion
spectral amplification in Aobayama

Fig.22 Spectral Amplification in the
THU building for the 2011 and 1978
earthquakes

DYNAMIC BEHAVIOR OF THU DAMAGED THU BUILDING
DURING THE 2011 GREAT EAST JAPAN EARTHQUAKE
Description of the damaged building and Observed Strong Motion
The THU building is a 9 story SRC (non-full web type) building and was constructed in 1969 andexperienced 1978 Miyagi-ken Oki earthquake. The observed acceleration waveforms of the 3components at 1st floor and 9th floor are shown in Fig.23. The configuration of the building and sensor
locations are shown in Fig.24. In the building, SMAC-MD type seismometer is installed at 1st and 9th
floor. From December, 2007, a continuous monitoring system (NetDAS/ MicroSMA) with sensors at176

1st, 5th and 9th floor has been operated (Motosaka et al., 2008). The system enables to measure frommicrotremor to strong motion.
10.05 6.75 6.75 10.05
33.6

Ⓔ

★

〃

4.0 8.0
⑨

⑧

〃
⑦

〃
⑥

Ⓓ

(a) 1st floor

⑤

④

③

Ⓑ

Ⓐ

1st fl. plan
１階平面図
● SMAC-MD

Ⓒ
Ⓑ

⑥

Ⓒ

〃
〃 8.0 4.0
〃
72.0
⑤
④
③
②
①

★
⑦

Ⓓ

②

★ MicroSMA

5th fl. plan

５階平面図
Ⓓ

★

Ⓒ

9th fl. plan

Ⓑ
⑦

⑥

S

⑤

④
N

③

②
W
９階平面図

E

32.9[m]EXPANSION JOINT

G.L(b) 9th floor
Fig.23 Observed records during the main shock

33.6[m]72.0[m]Fig.24 Configuration of THU Building and Sensor location

In the THU Building, long-term monitoring of dynamic characteristics has been performed bystrong motion observation, forced vibration test, microtremor observation, and etc, for about 40years
since the completion of the building in 1969 (Motosaka, et al., 2004, Motosaka, et al., 2011). After
experience of the structural damage due to 1978/6/12 Miyagi-ken Oki earthquake (Shiga et al., 1981),
seismic retrofit work was performed from autumn of 2000 to spring of 2001. It is noted that theseismic strength index, Is-value at the damaged 3 rd floor in the transverse direction increased from
0.53 to 0.84. Then, the building experienced the 2005 Miyagi-ken Oki earthquake, 2008 Iwate-Miyagi
Nairiku earthquake, and 2008 Iwate Northern Coast earthquake, and so on.
Photo 1 shows the damaged THU Building. The building was heavily damaged at bottom of 4
corner columns. The severe crack of the side shear wall due to possibly partial uplifting was suggested
at the level of third floor (Tsamba and Motosaka, 2011).

Photo 1 Damage feature of bottom of one of the damaged four corner columns of THU building177

Dynamic hysteretic behavior
To investigate the dynamic hysteretic characteristics, the acceleration records at 9th floor and 1st
floor are doubly integrated and the relative displacement is calculated. The maximum relative
displacement is 31cm in NS direction.
Fig.25 shows the dynamic hysteretic behavior based on force-displacement relation for the 16
time sections which are obtained from acceleration waveform at 9th floor and the relative
displacement. Findings from this figure are as follows.
1) Starting from linear behavior at smaller amplitude level, hysteresis shows the inverse S shapeslightly as recognized in section 5. Then shows linear behavior but the stiffness is reduced in
section 6 compared to section 1.
2) Then, with increasing displacement, the hysteresis shows softening and hysteretic loop is
recognized only for the larger displacement level. The hysteresis shows origin oriented behavior
as recognized in (section 7).
3) Then decreasing the displacement, the hysteresis shows the characteristic inverse S shape insection 9. Although the amplitude decreases from Section 9 to Section 10, this hysteresis leads
to stiffness reduction, which consistent with the dominant frequency reduction.
4) Then decreasing displacement gradually returns to linear behavior with the reduced stiffness insections from 13 to 16 compared to section 6. The stiffness change is consistent withmicrotremor observation before and after the earthquake.

1G=980cm/s/s

40 cm

Fig.25 Relative displacement waveform and Hysteresis loops for each time section (NS-Direction)

178

System Identification
To investigate non-stationary dynamic characteristics due to structural non-linearity, the system
identification technique using Kalman filter is used to determine natural frequency and damping factor
as equivalent SDOF system (Takahashi et al., 2010).
Fig.26 show the result of the identified system parameters, natural frequency and damping factor
for NS direction and EW direction, respectively. In these figures, the calculated relative displacement
waveform is compared to that obtained from observed records. As for the identified system parameters,
natural frequency and damping factor, the smoothed curves are shown in these figures. Findings
from the system identification results are as follows.
1) In the transverse (NS) direction, dominant frequency decrease down to about 0.8 Hz withincreasing amplitude and the dominant frequency is not changed even if amplitude is decreased.
2) The damping factor in the transverse direction increases with increasing the amplitude at time
section 7 in Fig.25 At the time sections with the inverse S type hysteresis, damping factor isdecreasing with increasing the amplitude.
3) In the longitudinal (EW) direction, dominant frequency decrease down to about 0.9 Hz but returnto about 1 Hz when amplitude level becomes small.
4) The smoothed damping factor in the longitudinal direction seems to be lager compared to theTransverse direction. This may be due to difference of hysteretic energy consumption.
20

20

0

0

-20
20

-20

Relative Displacement
40

60

80

100 120 140 160

180 200 220

20

0.2

0.2

0.1

0.1

0

0

Damping Factor
20

40

60

100 120 140 160

180 200 220

20
2.0

1.0

1.0

Natural Frequency
40

60

80

60

80

100 120 140 160

180 200 220

100 120 140 160

180 200 220

100 120 140 160

180 200 220

Damping Factor

80

2.0

0
20

Relative Displacement40

100 120 140 160

Time(s)180 200 220(a) NS (Transverse) direction

0
20

40

60

80

Natural Frequency
40

60

80

Time(s)(b) EW (Longitudinal) direction

Fig.26 Identified damping and Natural Frequency
Investigation of uplifting vibration
In case of structural vibration with partial uplift, odd number higher harmonics are induced in thehorizontal directions and even number higher harmonics are induced in the vertical direction(Motosaka and Nagano, 1993).
Fig.27 shows non-stationary characteristics expressed by wavelet coefficients of the 9th floor’s
acceleration waveform in the transverse direction for 10 sec time sections including the peak value.
Fig.28 (a) shows the wavelet coefficients of 9th floor for the vertical direction. Fig.28 (b) is the
wavelet coefficients of 1st floor for the vertical direction. Findings from these figures are as follows.
1) The dominant frequency corresponding to the two times frequency (about 2Hz) of the verticaldirection is clearly seen at large amplitude range corresponding to the time sections from 7 to 9.

179But the dominant frequency is not seen at the 1st floor.
2) This suggests the occurrence of partial uplift of the damaged building at the 3rd floor.
(a)

(b)

Fig.27 Acceleration waveform at 9F andwavelet transform

Fig.28 Wavelet transforms of acceleration in
the vertical direction at (a) 9F and (b) 1F

LONG TERM MONITORING OF DYNAMIC CHARACTRISTCS OF THU BUILDINGIn the building, earthquake observation has been performed since completion in 1969 andmicrotremor observations also have been performed. The forced vibration test was performed before
and after the retrofit work in 2000. The amplitude dependent dynamic characteristics have been
investigated (Motosaka et al., 2004).
Table 3 shows change of 1 st natural
Table 3 Change of fundamental frequency
frequency of the building based on not only the
Natural frequency (HZ)
Date
Event nameearthquake records of main shock andNS
EW
foreshock and together with micotremor records
2011/3/9
Microtremor
1.61
1.61
2011/3/9 Foreshock (Sanriku Oki)
1.26
1.26
before and after the earthquake events. It is2011/3/11
Microtremor
1.61
1.61
noted that the natural frequency of the two
Main shock (Phase A)
1.05
1.05
2011/3/11
directions due to microtremor observations
Main shock (Phase B)
0.78
0.88
were the same (1.61Hz) before and after the 3/9
2011/3/19
Microtremor
1.17
1.37
2011/3/19 Aftershock (Ibaraki-Ken)
0.93
1.16
foreshock and also the same (1.26Hz) in the
2011/5/3
Microtremor
1.17
1.37
two directions during the foreshock. But during
2011/5/31
Microtremor
1.37
1.48
the main shock, reduction of the natural
frequency is remarkable in NS direction compared to EW direction, which is consistent with thedamage feature of the building. The frequency reduction is large in the second phase (phase B). The
stiffness reduced up to 23% in NS direction and 37% in EW direction compared to the stiffness due tomicrotremor before the main shock. The stiffness in the microtremor level was reduced to 53% in NS
direction and 72% in EW direction. It is noted that the THU building was temporary repaired at thedamaged 3rd floor in May, which lead to the natural frequency increase from 1.17Hz to 1.37Hz in NS
direction and 1.37Hz to 1.48Hz in EW direction. But the microtremor observation at May 3 (before therepair work) shows no natural frequency change from March 19, even if the building was shaken by
the large aftershock on April 7 and April 11.
Table 4 shows the maximum acceleration list of major earthquake observation records at THU
building. Fig.29 shows the relation between the deflection angle and the natural period for both two
directions. In the figure, the different symbols are used for the 4 terms, namely, Term 1: From180

completion to 1978 earthquake, Term 2; After 1978 earthquake to retrofit work in 2000, Term 3: After
retrofit work to 2011 Tohoku Earthquake, Term4: After Tohoku earthquake. Furthermore Term 3 andTerm4 are divided into two terms.
Table 4

Maximum acceleration list of major earthquake observation records at THU building
Date

Magnitude

1978/2/20
1978/6/12
1998/9/15
2003/5/26
2003/7/26
2003/9/26
2005/8/16
2008/5/8
2008/6/14
2008/7/24
2011/3/9

6.7
7.4
5.2
7.1
6.2
8.0
7.2
7.0
7.2
6.8
7.2

2011/3/11

9.0

2011/3/19
2011/4/11
2011/4/12
2011/4/23
2011/7/10
2011/7/23
2011/7/25
2011/7/31

6.1
7.0
6.4
5.4
7.1
6.5
6.2
6.4

1 Floor (max.acc(cm/s/s)
NS
170
258
138

EW
114
203
451

33

27

87
19
88
59
37
207
333
15
72
24
17
21
10
48
36

81
22
70
77
34
216
330
18
70
28
27
18
11
62
31

9 Floor (max.acc(cm/s/s)
NS
421
1040
190
231
98
29
329
261
392
275
171
594
908
34
141
43
23
95
60
106
70

EW
298
523
379
264
102
22
287
226
293
367
89
617
728
56
172
84
57
58
42
99
45

Area name
Miyagi-Ken Oki
Miyagi-Ken Oki
Miyagi-Ken Southern
Miyagi-Ken Oki
Miyagi-Ken Northern
Tokachi Oki
Miyagi-Ken Oki
Ibaraki-ken Oki
Iwate-Miyagi inland
Iwate-Ken North CoastSanriku Oki(Phase A)
Off Pacific Coast Tohoku(Phase B)
Ibaraki-ken Northern
Fukushima-Ken Southern
Fukushima-Ken Oki
Fukushima-ken Oki
Sanriku Oki
Miyagi-Ken Oki
Ibaraki-ken Northern
Fukushima-ken Oki(b) EW (LN) direction(a) NS (TR) direction

Fig.29 Relation between deflection angle and 1st dominant period
Findings from this figure are as follows.
1) The amplitude level of the first phase (phase A) is smaller than that of the 1978 earthquake in
NS direction but the amplitude level of the second phase (phase B) became larger compared to1978 earthquake in the both directions.

1812) The change of the natural period due to the 2011 Tohoku Earthquake is lager in NS direction
compared to EW direction, which is consistent with the damage feature.
3) It is confirmed through the continuous observation that the dominant period at mictotremor
level is not changed if the deflection level is smaller than the experienced maximum deflection.

DAMAGE FEATURE OF THE DAMAGED AREA
DURING THE 1978 MIYAGI-KEN OKI EARTHQUAKEAs above mentioned, Oroshimachi area, the damaged area during 1978Miyagi-ken Oki
earthquake , which was located in the alluvial plain, was severely shaken during the 2011 earthquake
compared to Sumitomo site near Sendai station located on a diluvium plateau (refer to Fig. 15) .
In Oroshimachi area, only two buildings among
338 buildings were collapsed during the 3/11 main
shock but number of collapsed buildings wasincreased to 5 due to 4/7 severe after shock.
Considering many buildings were heavily
damaged during the 1978 earthquake, the buildings inthis area became strong due to effectiveness of theNorth
new building code and seismic reinforcement/retrofit.
Photo 2 shows the collapsed two buildings during the
Photo 2
Collapsed two buildings inmain shock. Both were constructed in 1969 andOroshimachi, Wakabayashi-ku, Sendai
experienced the 1978 earthquake. Estimation of
accumulated damage is important. Both the collapsed buildings are damaged in NS direction, which isconsistent with the ground motion characteristics in Fig.30. The author confirmed through witness by
two survived persons who were at the 1st floor of the left building in Photo 2 that the building was notcollapsed during the first phase (phase A) but collapsed during the second phase (phase B).

Fig.30 Comparison of observation record in the two horizontal directions at Oroshimachi andresponse spectra
SPECFIC STRUCTRAL DAMAGE
Damage of Pile foundation buildings
The authors inspected the damaged pile foundation buildings during the 1978 earthquake
immediately after the 2011 Tohoku earthquake. It was reported that 7 piles are inspected and twoamong 7 piles were repaired but not reinforced at that time (Shiga, 1980). Photo 3 shows the 14-story
SRC building for condominium, one of L shaped two buildings, connected by exp. joint each other,
was inclined by 1/56 due to main shock and extended the inclination up to 1/45. Fig.31 shows theresult of subsidence measurement at 11 points. The measured values in meter (shown as blue) are182

relative elevation from the reference point. In the inclined right building, the level differences are
31cm for 14m arm length in the south ( No.10 and No.11) and center (No.4 and No.3), which areconsistent with the inclination angle of 1/45. This subsidence measurement suggests the pile failure ofeast side due to dominant ground motion in the NS direction.
13.23

13.48 1

2

N

4

13.28

13.59
3

13.54 6

Photo 3.
Inclined 14-story SRC pilefoundation building; (left) Overall view,(right) Opening of expansion point part

13.54

5

13.55

13.26
7

8
13.55

9
13.48

10

13.57

11

Fig.31
Measurement of subsidence of thedamaged building
A 4-story RC building with pile foundation (Photo4) was inclined by 1/30 due to pile damage. No
damage was recognized in the superstructure. The
building was constructed in 1983 after execution of
the new building code. It was recognized thesurrounding soil was liquefied.
Photo 4. Inclined 4-story RC pile foundationbuilding; (left) Overall view (right) Subsided
bottom part of the south east corner column
Ceiling Board Damage
Many ceiling board drop accidents were occurred in the large span structures like culture hall andlarge store. The ceiling board damage killed 4 persons during the Tohoku earthquake.
Photo 5 show the damage feature of suspended ceiling board drop at a culture center hall in
Sendai, which the author inspected and investigated vibration characteristics based on microtremor
observation. Fig.32 shows the Fourier spectra at roof of the building. It is noted that the verticalmotion is induced at the roof due to horizontal input motion. In the design of the ceiling board, theceiling board system would be taken into the induced vertical motion as well as enough clearance forhorizontal motion. Judging from the damage feature, the drop seems to be caused by the lack ofstrength to the vertical motion and the unexpected collision between hanging bold and equipments
such as air conditioning duct. The seismic standard for vertical load of the ceiling board system would
be reconsidered especially for large span structures and also for the many numbers of displacement
cycles due to ground motion with long duration and also due to accompanied many aftershocks. It isalso important to recognize that the response of the ceiling board is affected by the vibration
characteristics of earthquake supporting soil and structure including roof slab. If resonance phenomena
occur, applied earthquake force would significantly large. For a lager ceiling board with area morethan 1,000m2, floor response spectral method would be needed. It is also important to consider thatceiling board system is recognized as the bending board supported by springs and vibration energy
should not be propagate horizontally (Motosaka, 2006).

183

Photo 5

Damage feature of ceiling board drop at a culture center hall in Sendai

Ave. Spectral Vel. Amp. (cm)2.0x10-3

Roof Center
屋根中央
Obs. point

EW
NS
UD

1.5

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)Fig.32

Dominant frequencies based on microtremor measurement at the center ofroof at the damaged culture center hall in Sendai

CONCLUSIONSIn this paper, ground motion characteristics and the related building damage during the 2011
Great East Japan earthquake (M9.0) are described. Buildings with appropriate seismic
reinforcement/retrofit were mostly escaped from damage, which indicates effectiveness of the seismic
reinforcement/retrofit. But the structural damage caused by ground motion amplification wasrecognized. The following learning and lessons from the 2011 earthquake are addressed for stronger
earthquake countermeasures of urban and building structures.
1) Necessity of the seismic microzoning considering ground motion difference due to geologicalconditions,2) Necessity of appropriate seismic indices corresponding to objective building damage,3) Reconsideration of the setting place / setting method of the seismometer,
4) Necessity to evaluate the safety of structural elements for number of displacement cycles due tothe long-duration earthquake and repetition by many aftershocks,5) Consideration of non-stationary of ground motion the nonlinearity of the building for the huge
earthquake,6) Total balance of structural element, non-structural elements, and equipments, and also balance offoundation and superstructure for synthetic seismic performance of the whole building,7) Evaluation of residue performance of the buildings damaged by past earthquakes and thisearthquake.

184

ACKNOWLEDGMENTS
Strong motion records of K-NET were used in this study was observed by NIED. The strong
motion record by SMAC-MD at THU building is provided by Building Research Institute. The author
thanks the related persons of the organizations. The author thanks Dr. Akenori Shibata, Prof. Emeritus
of Tohoku University, who provided valuable advices. The author also thanks Assoc. Prof. Susumu
Ohno and my graduate students, Ms. Tsamba Tsoggerel and Mr. Kazushi Yoshida who contributed toprepare the materials in this paper.

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