zMessages from Departments and Centers of NILIM  To incorporate the latest findings inseismology and earthquake engineering in
the practice of seismic design

PhotoNISHIYAMA Isao, Director
Building Department(Key words) Headquarters for Earthquake Research Promotion, seismic motion prediction, building seismic design,Comprehensive Project on Sophistication of Seismic Design

2. Matters to consider when using seismic motion
prediction for practical seismic design work
Seismic motion predictions for various types of earthquake
are also made by the Central Disaster Management Council andothers, besides the Earthquake HQ mentioned above. Studies
are also being made, from different aspects, by theArchitectural Institute of Japan and the Japan Society of Civil
Engineers, among others. In some cases, these have proudly
announced completely different seismic motion predictions forthe same location during the same earthquake, leading
seismologists to wonder which of them is actually to bebelieved.
Quite aside from analytical techniques, seismic motion
prediction depends on the intricacy of epicenter models
describing how the destruction advances from the epicenter,
underground structure models showing the course ofpropagation from the epicenter to the location where seismic
motion is to be predicted, and so on. In the proposals by
Earthquake HQ, seismic motion is predicted with these models

as givens; there is not necessarily enough explanation as to how
the predicted seismic motion is influenced by error inherent in
the employed modeling itself. As a result, we must first
ascertain the impact of this error when applying thesepredictions to practical seismic design work.
While the predicted seismic motion is generally assessed atground level, the seismic motion used in seismic design is theinput seismic motion observed directly below the building.
Essentially, therefore, these are two different things; it is really
not appropriate to apply the proposed seismic motion
prediction to practicalseismic design work, as if it were input
seismic motion, without first studying the relationship between
the two.
1000

Peak acceleration

500
Peak Acc. at Base (cm/s2)

1. Introduction
Recently, it has become quite common to see 3-dimensional
reconstructions of massive earthquakes occurring along theNankai Trough. Here, the processes whereby an earthquake
occurs and radial earthquake waves spread from the epicenter
to the Japanese archipelago are realistically reproduced. We see
how high-rise buildings in the center of the capital region swayfrom side to side, and how major fires are started. When I firstsaw Sakyo Komatsu’s film “Nihon Chinbotsu” (Japan Sinks), it
all felt very artificial, but these new visuals are a world apartfrom those old attempts. And it’s not just the video technologythat has progressed; we have accumulated so much morescientific knowledge on earthquakes since then.
When the Great Hanshin-Awaji Earthquake struck in 1995,
it led to the establishment of the Headquarters for Earthquake
Research Promotion (Earthquake HQ)1), a body for unified
promotion of research on earthquakes. Every year, it updates its
website with announcements of new research findings. In Julylast year, it uploaded a compilation of these in the form of“National Seismic Hazard Maps”, followed by “Long-period
Seismic Hazard Maps: 2009 Prototype” in September.
For a hypothetical earthquake, seismic motion is predictedby following a “recipe” (so called because the same results will
be produced, whoever uses it), setting models for the epicenterand underground structure, etc. As a specific example, theshaking of the Aichi Prefectural Government Buildings during
an earthquake in the Tonankai area is shown in the form ofwaves. Given sufficient time, however, it is even possible tocalculate seismic motion in the grounds of individual building
structures during the hypothetical earthquake.
We now need to make studies aimed at using these seismic
motion predictions, proposed from the latest research, forpractical seismic design work.

200100502010
ABase = 0.38 AGL5

ABase = 0.36 AGL

XY22510 20
50 100 200
Peak Acc. on GL (cm/s2)

500 1000

Fig. 1 Strong motion observation inside and outside
Hachinohe City Hall (Source: Building Research Institute)
Fig. 1 compares the results of strong motion observation
directly beneath Hachinohe City Hall and at ground leveladjacent to the building (including observed data from theIwate-Ken Engan-Hokubu earthquake of July 24th, 2008). The
vertical axis shows observation results directly beneath thebuildings. Compared to the observation results at ground level,
as shown in the horizontal axis, this shows an acceleration ofaround 40% less. If the relationship between the two is formallyconverted to the difference in JMA (Japan MeteorologicalAgency) instrumental seismic intensity, input seismic motion
will be around 0.75 smaller than the seismic motion at groundlevel. Although input loss is known to result from dynamic
interaction and other factors, this makes it perfectly clear thatseismic motion prediction at ground level must be treatedseparately from input seismic motion as the force that actually
impacts on buildings.
3. “Notification waves” in the Building Standards Law

zMessages from Departments and Centers of NILIM

Building’sᑪ▽‛䈱ടㅦᐲ䊂䊷䉺acceleration
dataGathering᷹ⷰ䊂䊷䉺෼㓸
observed dataSample 䉰䊮䊒䊦ᑪ▽‛䌁
building A䉰䊮䊒䊦ᑪ▽‛䌂䉰䊮䊒䊦ᑪ▽‛䌃Samplebuilding B Sample
building C࿾㔡⸘
Seismometer

Acceleration
data at ground level࿾⴫㕙䈱ടㅦᐲ䊂䊷䉺丆丶䷾

DataData丆丶䷾Data丆丶
䷾丆丶
䷾

4. Comprehensive Project on Sophistication of Seismic
Design – Developing technology for evaluating the seismic
performance of building structures in response to theadvance of seismic motion information –To study whether seismic motion prediction based on thelatest findings in seismology and earthquake engineering canbe applied as they are to building seismic design, and toascertain what kind of study is needed in order to use it, etc., wewill start a Comprehensive Project on Sophistication of Seismic
Design3) in fiscal 2010.
The core of research in this project will lie in surveying therelationship between seismic motion at ground level and input
seismic motion by studying the soil-structure interaction model,using existing observed data of strong motion inside andoutside buildings. Another important component will be toenumerate the relationship between input seismic motion andseismic motion at ground level for each ground condition,building scale, and frequency. This will be done byaccumulating observed data of strong motion inside and outsidebuildings for ground conditions, structural types and scales ofbuilding structure not handled by existing strong motion
observation.

Specifically, by conducting the study shown in Fig. 2, wewill develop 1) techniques for assessing earthquake force
taking into account the properties of both the building and theground, 2) methods of continuously improving seismic designtechnology based on strong motion observation results, and 3)
efficient seismic restoration technology, including groundfoundations, based on strong motion observation results.
To conduct this research, it will also be vital to have thecooperation of the private sector, universities and other related
institutions, and to gather and analyze earthquake observation
records from as many building structures as possible. As such,
we look forward to significant cooperation from related
institutions and individuals.

Data丆丶䷾

An Enforcement Order was used to provide performancestandards in 2000 following the 1998 amendment to the
Building Standards Law. The Order specified the acceleration
response spectrum (5% damping) at engineering foundations,converted from the earthquake force that had been used inseismic regulations until then (the 1981 amendment to the
Building Standards Law, or the New Seismic Design Method).
This is known as the notification spectrum, and the“notification wave” that fits this spectrum is used as the input
seismic motion in time-history response analysis for buildings
approval.
While it has already been pointed out that input seismic
motion should be distinguished from seismic motion at groundlevel, instrumental seismic intensity is sometimes calculated
formally from the notification wave created as a unidirectional
wave. In Soil Type 2, instrumental seismic intensity has been
known to reach around 5.9. Since the instrumental seismic
intensity during an actual earthquake is calculated from a3-directional component earthquake wave, if we similarly
consider the notification wave with a 3-directional component,
the instrumental seismic intensity will become about 6.05.
From this numerical fact alone, some have expressed concernthat buildings designed under existing seismic design standards
will invariably collapse if the earthquake magnitude is larger
than the instrumental seismic intensity of 6.05 (i.e. 6+ or 7). In
fact, however, it is not so simple.
This is because an Interim Report2) from the Building
Earthquake Damage Survey Committee stated that buildings
designed in line with the New Seismic Design Method
generally manifested good seismic performance, following
damage surveys in Kobe City and surrounding areas that
suffered human judged seismic intensity 7 during the Great
Hanshin-Awaji Earthquake.
Why was there so little terminal damage even in an area
subjected to human judged seismic intensity 7, when the
instrumental seismic intensity formally calculated from thenotification wave was about 6.05? It is conceivable that even inareas with human judged seismic intensity 7, the input seismic
motion may in reality have been small, for the reasons shown in
Fig. 1. Another reason may well be the point that, since theminimum specified value is used as the strength of materials
used in practical seismic design work, there is already a margin
in there; an increase in resistance could also be anticipated due
to redistribution of stress after plasticization of the buildings;
and so on.

DataClarify the relationship between seismic motion at ground level and input࿾⴫㕙਄䈪䈱࿾㔡േ䈫ᑪ‛⋥ਅ䈮૞↪䈜䉎౉ജ࿾㔡േ䈫䈱㑐
seismic motion working directly beneath buildingsଥ䉕᣿䉌䈎䈮䈜䉎

Fig. 2 Image of research in the Comprehensive Project on
Sophistication of Seismic Design
5. Conclusion
Methods of seismic design for building structures have learnt
many lessons from past earthquakes, leading to their presentformat.
To boldly incorporate cutting-edge findings from seismology
and earthquake engineering, as presented by Earthquake HQand others, in practical seismic design, we will need to achievea good balance between research on aspects of seismic motion
and research on aspects of building structures. We will alsoneed to aim for an even higher level of regulation onperformance than heretofore.
In the Building Department, as one aspect of this kind ofresearch, we plan to embark on the Comprehensive Project on
Sophistication of Seismic Design from fiscal 2010.
References
1. http://www.jishin.go.jp/main/index.html
2.http://www.lib.kobe-u.ac.jp/directory/eqb/book/11-43/index.
html
3. http://www.nilim.go.jp/lab/hcg/index.htm