“road rating maps for comfortable drive” into car navigation system

Tokyo Gate Bridge 2

Solar Heat-blocking Pavement 5

Seismic Retrofit Technique of Asphalt Concrete Pavements 8

Implementation of tsunami disaster management 11

C O N T E N T S

Infrastructure Development Institute – Japan (IDI) New Kojimachi Bldg, 5-3-23, Kojimachi, Chiyoda-ku, Tokyo, 102-0083, JAPAN

Tel: +81-3-3263-7813 Fax: +81-3-3230-4030 E-Mail: [email protected] Homepage: http://www.idi.or.jp/english/00index.htm

Tokyo Gate Bridge

IDIIDI QUARTERLYQUARTERLY

Japanese Infrastructure Newsletter

I n f r a s t r u c t u r e D e v e l o p m e n t I n s t i t u t e — J A P A N

July 2012 No.60

Infrastructure Development Institute - Japan

July 2012 No.60

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Tokyo Gate Bridge

1.Tokyo Port Seaside Road and Tokyo Gate Bridge

Tokyo Gate Bridge which was designed and

constructed by Ministry of Land, Infrastrucature,

Transport and Tourism (MLIT), was opened to traffic

in February, 2012. This is a “continuous truss-box

composite bridge” with total length 2,618m, of which

1,618m is crossing offshore portion, and this is one of

the largest continuous truss bridges in the world.

Tokyo Gate Bridge is a part of Tokyo Port Seaside

Road. Due to the recent increase of the container

cargo in port of Tokyo, traffic jam caused by container

trailer has been observed in the neighboring road.

After opening of the Tokyo Port Seaside Road,

commodity distribution in waterfront area will become

smooth, and traffic jam in Tokyo Bay Coastal

Expressway will be alleviated (cf. map 1).

The bridge is located close to the Tokyo International

Airport (Haneda), so the bridge height is restricted

because the airplane flies over the bridge. And the

bridge crosses over navigational channel, hence enough

clearance under the deck should be maintained. In

order to comply with these severe requirements, MLIT

have selected a quite unique truss design for this

bridge. The truss bridge, having 87.8m of structural

height, also having 54.6m of clearance under the deck,

is nicknamed “Dinosaur Bridge” because it looks like

two dinosaurs are confronting with each other. And

will possibly become a future tourist spot.

2.New Technology used for Tokyo Gate Bridge

Tokyo Gate Bridge is an economically efficient bridge

by achieving cost-cutting with the introduction of new

technologies. Overall bridge performances are

optimized through the technological collaboration of

superstructure experts and substructure experts.

Maintenance cost will decrease and lifecycle cost is

expected to get down. Followings are new

technologies introduced in this bridge.

(1)Adoption of steel deck structure with high fatigue

durability

Tokyo Gate Bridge has a long center span (440m) due

to several restrictions for construction. Since MLIT

have to reduce the dead weight of superstructure, steel

deck structure is adopted throughout the whole bridge.

But many fatigue failure examples were reported in

conventional bridge adopting steel deck structure. So

MLIT have introduced FEM analysis at the design

stage of Tokyo Gate Bridge, and investigated steel deck

structure with high fatigue durability by accurately

reflecting local stress and main stress into design that

Map 1: Tokyo Port Seaside Road and TokyoGate Bridge

（Source : Tokyo Port Office, MLIT）


July 2012 No.60

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is hard to estimate in the conventional structural

analysis (Fig. 1). Investigation results were verified

with full-scale load test and also fatigue test.

Fig. 1: Deck Structure (Source : Tokyo Port Office, MLIT)

(2)Adoption of weldable high strength steel for bridge

structure

For the large scale truss bridge, high strength steel

should be used in order to decrease the dead load of

superstructure, but the conventional high strength steel

need a preheating process before welding, wasting an

extra time in order to avoid cracking, so the welding

efficiency is not necessarily satisfactory and construction

cost tend to be expensive. For the Tokyo Gate Bridge,

MLIT have adopted “highly strong and tough and has

excellent weldability and cold formability Bridge

High-performance Steel (BHS)”. The BHS requires no

preheating before welding, so the welding time could

dramatically be shortened and quick construction time

was achieved. Then MLIT could reduce 3% of the steel

weight, and also reduced 12% of the construction cost.

Reduction of the steel weight means the reduction of the

size of bridge foundation, so adoption of BHS had greatly

contributed to the overall cost reduction of this project.

(3)Adoption of large scale sliding seismic isolation plate

bearings

For the Tokyo Gate Bridge, aseismic base isolation is

applied at the bearing of main pier. The horizontal

force of Tokyo Gate Bridge caused by the quake

vibration is three times stronger than the conventional

sliding plate bearings durability. So if MLIT use

conventional lead rubber bearings, the following

problems will arise.

① Too large displacement will occur

② Maintenance of exposed rubber is difficult

③ Conventional manufacturing facility is unable

to make such big size

So MLIT quit to use lead rubber bearings and adopted

sliding plate bearings. This is two different types of

bearings (load support plate and rubber buffer), and tried

to make bearings compact. Load support plate can

support the vertical load, and absorbs horizontal load by

the friction between Teflon plate and stainless steel plate.

Rubber buffer supports the horizontal plate and absorbs

vibration force with elastic deformation. In principle,

vertical force is supported by metal plates, and horizontal

force is supported by rubber buffers (Fig. 2).


July 2012 No.60

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Fig.3 : Steel pipe sheet pile well foundation(Source : Tokyo Port Office, MLIT)

Fig.2 : Sliding plate bearing (Source : Tokyo Port Office, MLIT)

(4)Adoption of large-scale steel pipe sheet pile well

foundation

The foundation of Tokyo Gate Bridge is a large-scale

steel pipe sheet pile well foundation. The shear

resistance characteristic of the interlocking joints that

connects each steel pipe sheet pile is very important

when designing quake-resistant foundation.

Normally in order to prevent deformation, 117 piles

will be required, but in the case of well foundation of

Tokyo Gate Bridge, only 98 piles were enough to

maintain required shear resistance and resulted to the

cost saving. This was achieved by, ① putting some

checkered bumps inside the interlocking joint, ② the

strength of infill mortar is increased to 40MPa (Fig. 3).


July 2012 No.60

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Solar Heat-blocking Pavement

-Just how cool is environmentally friendly paving?- NIPPO CORPORATION

Partly due to the proliferation of air conditioners

across Japan, and perhaps aggravated by global

warming issues, summers in Japanese conurbations

have recently seemed hotter than ever. Although

statistical averages may not reveal a clear-cut

difference, it is important to note that these represent

shade temperatures, whereas, in real-world scenarios,

some asphalt paving can turn outdoor conditions into

something akin to an open-air oven, with temperatures

climbing to 60°C. While some have turned to low-tech

solutions, like simply hosing down pavements in

pedestrian areas, others have undertaken research into

how best to tackle the primary problem – excessive

heat – as well as mitigating any secondary issues, such

as rutting, aging and fatigue, each of which can be

aggravated by high temperatures, by assessing the

structure of the paving itself. NIPPO Corporation in

Japan has developed a paving technology called “Solar

Heat-blocking Pavement” that serves to substantially

reduce solar heating.

The technology is premised on the concept of coating

existing paving with a surface designed to reflect –

rather than absorb – solar and infrared rays; but not

the visible spectrum, since that could prove dazzling to

road users (see Photo 1 and Figure 1). Solar and

infrared ray reflectivity is represented by the term

“albedo”. For instance, a higher albedo means that

the pavement surface strongly reflects infrared rays,

whereas a lower albedo indicates that the pavement

readily absorbs such rays. Clearly, this makes a high

albedo factor more desirable to prevent an excessive

build up of temperatures, since a low albedo is precisely

the problem with existing asphalt surfaces. Therefore,

a solar energy-reflecting pigment was developed to

prevent absorption of infrared rays at the surface.

Photo 1: Solar Heat-blocking Pavement

Figure 1: Concept of Solar Heat-blocking Pavement


July 2012 No.60

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In order to demonstrate albedo

characteristics, a comparison was made

between three surfaces: conventional

paving (i.e. dense graded asphalt

pavement), solar heat-blocking pavement,

and ordinary paint. In this case, the

paint was selected to closely match the

color of the solar heat-blocking pavement,

which is grey, whereas conventional

pavement is essentially black. Following

is a graph showing just how these three

materials reflect rays of different

wavelengths, ranging from the visible spectrum (about

390 to 750 nm) through the near and medium infrared

spectra (Fig. 2). It is immediately apparent from this

figure that although the grey solar heat-blocking

pavement and paint share very similar albedo

characteristics in the visible range – i.e. they are both

slightly more reflective that black asphalt, there is a

marked divergence in the near infrared zone, with the

solar heat-blocking pavement almost reaching a ninety

percent albedo rating across a wide spectrum.

Figure 3: Effect of temperature reduction

A further examination was conducted on how these

two contrasting paving materials perform under

identical conditions in the field. As illustrated in

Figure 3, whenever the temperatures peaked in the

early afternoon, the heat-blocking surface, which

topped out at about 42°C, was some 16°C cooler than

its asphalt equivalent [58°C]. This is a convincing

demonstration of the benefits – certainly from the

perspective of pedestrian comfort – of using solar

heat-blocking pavement in regions subject to hot

summers.

Insofar as this achieves the

primary goal, this is clearly

progress. But what of the

secondary considerations or

other complications, such as its

long-term performance and

further improvements in the

technology? The researchers

considered it both necessary and

prudent to assess its durability

and the surface temperature

under severe usage conditions over an extended period.

Figure 2: Albedo characteristics of solar reflective pigment


July 2012 No.60

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To this end, permission was obtained to apply the

reflective layer to part of the taxiway of an

international airport (see Photo 2). The extent of any

rutting to the two surfaces (i.e. dense graded pavement

and solar heat-blocking pavement) was then regularly

monitored. The results of this aspect of the four-year

experiment are presented in Fig. 4. From the graph, it

is readily apparent that the solar heat-blocking

pavement (S.H.P.) suffers ruts of less than half the

depth of conventional paving, with most of the rutting

for both surfaces occurring in the first two years.

From this point on (at least within the experimental

timeframe), further damage seems minimal.

What then of people’s thermal sensation on these

surfaces? A comparative trial was conducted during a

hot summer’s day when the external temperature

ranged between 30°C and 35°C. Under these

conditions, the unshaded pavement surface

temperatures were found to vary by as much as 12°C.

Photo 3: Volunteers in photographic image

Left: Conventional pavement

Right: Solar heat-blocking pavement

Photo 4: Volunteers in thermographic image

(Surface temperature: Approx 38°C)

Photos 3 and 4 show the photographic and

thermographic images of two similarly clothed men

standing on a test bed of the two surfaces. Comparing the

two images, it is apparent that the surface temperatures of

the two pavements were significantly different. As shown

in Photo 4, the conventional surface is colored white in the

sunny areas, which indicates a surface temperature of

more than 51°C, whereas the solar heat-blocking pavement

is a reddish-orange hue, representing a surface

temperature of around 46.5°C. The effectiveness of the

Figure 4: Changes in the maximum rut depth over four years

Photo 2: Application to an airport taxiway


July 2012 No.60

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solar heat-blocking pavement is evident from the

thermographic image. This contributes to an improved

thermal sensation, especially around the feet.

In Japan, this type of heat-reducing surface has now

been used for some half million square meters of

pavement, not only as road surfaces, but also in parking

lots, public parks and rest areas (see Photos 5 & 6).

Contact

Osamu TANABE

NIPPO CORPORATION

Tel: +81-3-3563-6743 Fax:+81-3-3535-0040

e-mail: [email protected]

Seismic Retrofit Technique of Asphalt Concrete Pavements

Newly developed asphalt concrete pavement structure to keep the emergency traffic remain in service despite severe earthquake

NIPPO CORPORATION developed a seismic retrofit

technique of asphalt concrete pavements called

“Hazard Reducing Bed (HRB)” through joint

industry-academia research program with Prof Hideki

OHTA of Chuo University in 2011.

Reducing the risk of earthquake-induced damage to

road is needed to promote safety and disaster

mitigation and recovery. One of the responsibilities of

road administrators and industrial companies is to

maintain or rapidly resume its essential road and

business operations in the event of severe earthquakes.

Many road administrators and companies in Japan

have started to establish a so-called Business

Continuity Plan (BCP) to ensure that they can

maintain key operations in the event of a major

disaster and minimize negative effects on user,

customers and suppliers.

Road pavements which are adjacent to highway

structures such as bridges and box culverts are often

damaged due to the severe differential settlement of

embankments around abutments and wing walls by

severe earthquakes. In addition, liquefaction causes

severe failure of wing walls and approaches. Traffic is

easily intercepted by the earthquake induced damage

to road pavements. Keeping the emergency traffic

remain in service despite severe earthquake is the most

important subject of BCM.

HRB is a composite structure consisted of compacted

crushed stone layer, geo-grid and post-tensioning rigid

anchors. The high flexural rigidity of HRB is for

Photo 5: Application as a road surface

(Ikegami, Tokyo)

Photo 6: Application in a park

(Kokyogaien National Gardens)


July 2012 No.60

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overcoming weakness of base course or subgrade in

tension and flex/bending.

Compacted crushed stone is a main material using

HRB. Selection of soil material is very important to

keep the reinforced effect of its structure. Crushed

stone for mechanical stabilization is the best material

due to the high compression and shear strength.

Geo-grids are placed at upper, upper middle, lower

middle and lower surface of compacted layer for

overcoming weakness of subgrade in tension. Rigid

steel anchors are vertically penetrated from the top to

the bottom layer and locked by anchored to the lower

geo-grid. Confining by the anchors is the application of

both compressive and confined force to the compacted

layers, and gives a pre-tensile force to geo-grids.

Structure of Hazard Reducing Bed (HRB) for seismic

retrofit of asphalt concrete pavement

Full scale in-situ test of Hazard Reducing Bed (HRB) to simulate the severe differential settlement after

earthquakes (550mm diferential settlement, Left side:Hazard Reducing Bed, Right side:Normal Pavement)


July 2012 No.60

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Full scale in-situ test was carried out to verify the

performance of HRB in the test yard, Saitama, Japan

in 2011. The trial embankment constructed was 50m

length, 3.6m width and 2.5m height at the top of

embankment with steel deck of 10m length and 7m

width. The experiments to simulate the severe

earthquake-induced damage began by statically juck

down the steel deck of 10m length using ten

multi-controlled hydraulic jucks, which were

supporting steel deck. Structure of asphalt concrete

pavement with HRB consisted of asphalt concrete of

50mm thickness, base course of 300mm thickness and

HRB of 600mm. Four sheets of geo-grid (tensile

strength of 200kN/m, maximum strain of 4.5%) were

placed at every 200mm height of HRB layer. After

every placement of geo-grids, the crushed stone

(maximum particle size of 40mm) was spread over up to

200mm thickness and fully compacted by the vibration

roller and tire roller. The degree of compaction was

about 95%. Rigid steel anchors were set by the pitch

of 0.45-0.60 in square. Confined load by the anchors

was 30kN. Trial pavement on normal subgrade was

asphalt concrete of 50mm thickness, base course of

300mm thickness and subgrade of 600mm crushed

stone layer for comparing with the performance of

asphalt pavement with HRB.

The result of full-scale in-situ test shows HRB give the

smooth surface propile of asphalt pavement and good

trafficability, however the heavy cracks and faulting is

occurred on asphalt pavement on normal subgrade so

that the trafficability can not be kept at all.

In Nov. 2011, NIPPO CORPORATION constructed

HRB on the Highway embankment of Jyouban

Expressway in Fukushima, Japan. Excessive

settlement and deformation of the embankment was

occurred by the earthquake induced damages of the

Great East-Japan Earthquake in Mar. 2011. The

purpose of application of HRB is Seismic

Reinforcement of this Highway Embankments.

In this paper, the newly developed seismic retrofit

technique of asphalt pavements using HRB included its

structure, the results of full scale in-situ tests and its

application

Application of HRB for Seismic Reinforcement

inJyouban Expressway between Souma and

Minami-Souma, Fukushima, Japan (2011)

are described. HRB as a seismic retrofit of asphalt

pavement can be rapidly constructed, so it is realistic

enough to apply HRB for road in service. Full scale

in-situ tests show the good trafficability and durability

of asphalt pavement on HRB after the forced

settlement to simulate the severe earthquake-induced

damage. It can be concluded that HRB is fully expected

as a tool for use in BCP of road administrators and

industrial companies to promote safety and disaster

mitigation and recovery of road in future.

Contact

Tsutomu ISHIGAKI D.Eng.

Senior Research Engineer

NIPPO CORPORATION

TEL: +81-48-624-0755 / FAX: +81-48-624-0797

E-mail: [email protected]


July 2012 No.60

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Implementation of tsunami disaster management

On March 11th 2011, the Great East Japan

Earthquake and subsequent tsunami had attacked east

Japan, and the wide coastal areas along Pacific coast in

Tohoku had suffered catastrophic damages. Since

then, Japanese government is trying to take all

possible countermeasures so that this kind of tragedy

may never happen again.

Among disaster victims reaching 20,000 in this

quake, most of them were hit by tsunami. In the past,

we have experienced several tsunami attacks in Japan,

but none of them can be compared with the giant

tsunami of last year which caused so many victims and

devastating damages in the wide area. So the laws

and regulations, as well as technical standard has not

necessarily been well established until then.

The tsunami had destroyed not only seacoast

protective facilities such as levee or sea wall, but also

attacked hinterland areas and washed away city

streets and residential districts. In order to prevent

possible tsunami disaster in future, coast protection

facilities should be reconstructed and reinforced having

with tough capability. Also it is urgently required to

build tsunami-prepared local community, and also

required to enhance measures, software and

methodology of the early warning and evacuation

systems.

During one year after the outbreak of the Great East

Japan Earthquake, Japanese government had

developed a legal framework and technical standard in

order to alleviate the tsunami disaster damage. In

this report, we will introduce these legal system and

technical standard mainly developed by the Ministry of

Land, Infrastructure, Transport and Tourism (MLIT).

Rikuzen-takata city

photo by OYO Corporation

1.Tsunami countermeasure promotion law

The basic principle of the tsunami countermeasure is

the law promulgated in June, 2011, titled “Tsunami

countermeasure promotion law”. The objective of this

law is to promote comprehensive and effective

countermeasures in order to protect people from

tsunami disaster, as well as to maintain social order

and to secure public welfare.

(1)Basic concept

In case of the tsunami disaster, if individual person

takes quick and appropriate action, human damages

could be reduced substantially. In considering

tsunami countermeasure, the software side activity

such as disaster education and drill is also required in

addition to the construction of hardware facilities such

as coastal levee and evacuation facilities.

We will enhance tsunami observation facilities to

alleviate disaster, and will promote investigation and

research activities. Since tsunami spreads wide areas

on earth, we have to continue observation and research

activities in collaboration with other countries.


July 2012 No.60

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(2)Tsunami countermeasure from software viewpoint

Depending on the local characteristics, and based on

the latest research results, we will assume the magnitude

of tsunami, and the extent of multiple damages caused by

the tsunami. Then we will make tsunami evacuation

plan and make it available to the public.

We will set up systems that can issue quick and

proper warning, evacuation order, and we will try to

disseminate information on tsunami damages to the

general public with using visual power. Also, we will

implement effective visual tsunami education and

evacuation drill through school education.

(3)Tsunami countermeasure from hardware viewpoint

We will construct and maintain tsunami

countermeasure facilities based on the latest

information available. We will maintain and improve

existing facilities. We will reinforce and upgrade

coastal levee and embankments. We will nominate

tsunami evacuation facility, and will construct public

facilities that can be used for tsunami disaster

prevention. We will safeguard hazardous material

handling facilities from tsunami attacks.

We will take tsunami attack into consideration when

we carry on urban development by restricting residential

land development, and constructing sturdy building near

shore lines. When it comes to the reconstruction

activities in tsunami-hit areas, we will place an emphasis

on local industry restoration and job creation.

(4)Others

By setting November 5th, as Tsunami Disaster

Prevention Day, we will attract public attention and

deepen their understandings. We will investigate

financial and tax benefits for the promotion of tsunami

countermeasure and/or evacuation facility construction.

We will make financial assistance for the development

of hazard map and photo images. Since tsunami

spreads wide areas on earth, we have to continue

observation and research activities in collaboration

with other countries.

2.Basic concept for the restoration of damaged

coastal levee

On July, 2011, “Assumed tsunami height for design”

was issued for the coastal levee. On November, 2011,

“Basic concept for the restoration of damaged coastal

levee” was proposed. The following 3 points are basic

concept for the restoration of damaged coastal levee.

(1) We will determine the size of tsunami and its

height for levee design purpose

(2) We will adopt such design, that in case actual

tsunami exceeds the design height, the levee still

stands for alleviating tsunami damages.

(3) Quake-resistance countermeasures are necessary

for levees against such earthquake that causes

tsunami.

(1)How to determine tsunami height: Standard for the

decision of the coastal levee height:

By taking up some portions of consecutive coast line

having similar natural characteristics, we will fix basic

parameters.

(Tsunami height design procedure)

① By checking the historical record in the past, and

studying the evidence of the past tsunami height,

we will list up tsunami height in the past.

② With using computer simulation, we will calculate

the future tsunami height.

③ Making tsunami height graphs for each coastal

areas, we will categorize tsunami according to its

frequency (once in decades, once in hundred year,

and so on)

④ Based on the result obtained in the above ③,

neighboring coastline administrator will make


July 2012 No.60

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exchange of opinions and determine the

anticipated tsunami height.

Top height of the levee will duly be decided by the

coastline administrator, based on the design tsunami

height, taking all the factors into consideration such as

environmental preservation, natural scenery,

economics, maintenance easiness, construction

easiness and public utilizations.

(2)Adoption of levee strcuture that can withstand

unexpectedly high tsunami height

We have analyzed coastal levee damages and its

mechanism caused by the actual tsunami hit on March,

2011. As a result of this study, we have chosen some

specific levee design structure that demonstrates an

unprecedented ability to withstand such tsunami that

has over design height.

①Scouring prevention at the bottom of back slope

After tsunami overflows the coastal levee, it flows

down on the back slope with accelerating flow velocity.

Then the water stream scours the bottom ground of the

back slope and causes damage (cf. Fig.1). In order to

prevent this, we will place a protective structure at the

bottom and cover the structure. In order to slow the

flowing speed, the back slope angle is turned to be mild

.

②Flow-away prevention of levee crown protective structure,

back slope covering structure, front slope covering

structure. Wash-away prevention of the levee body soil.

When tsunami overflows the levee, crown protective

structure, back slope covering structure, front slope

covering structure will flow away. And the levee body

soil will be washed away from the clearance of the

structure. In order to prevent this, the thickness is

increased for the protective and covering structures.

Also the connections of these individual structures

should be tightened.

③Prevention of parapet collapse

Parapet blocks tidal wave or splash flowing into coast

lines. In case of tsunami attack, the structure

sometimes collapses to the land side, sometimes

collapses to the sea side by backwash. In the design

stage, if we select outer force is tsunami instead of

storm surge, earth fill should be made to the top of the

levee structure in order to prevent crumble, or

sometimes strengthen parapet with reinforced bar. (cf.

Fig.2).

Fig. 1 Scouring prevention at the bottom of back slope (Source: Summary of the report; ”Basic concept for the restoration of coastal levee damaged by the 2011 off the Pacific

coast of Tohoku Earthquake and Tsunami” Coastal Tsunami Countermeasure Investigation Committee, MLIT)


July 2012 No.60

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(3)A key consideration for the quake-resistance

countermeasures

The coastal levee should withstand the first

earthquake that causes tsunami. Tsunami may come

after twenty, thirty, or forty minutes after quake. If

the coastal levee were all destroyed by the first quake

vibration, it will be useless for the tsunami coming

thirty minutes later. So the quake resistance

capability should be considered.

Traditionally, we are only concerned about the

damages caused by quake vibrations. But in the case

of last year’s giant quake, coastal levee had suffered

the effect of the ground sinkage and ground

liquidations. Hence the effect of sinkage and

liquidation should also be considered and required top

height should be secured.

In case when ground sinkage is estimated as a

result of fault movement following the outbreak of

huge quake: Using computer fault model, the

degree of ground sinkage should be calculated

beforehand, and the height of levee should be

adjusted by adding sinking depth.

In case when ground liquidation is estimated:

Appropriate countermeasure should be taken.

And the height of levee should be adjusted by

adding sinkage of levee.

3.Proposal for the criteria for issuing tsunami

warning and content of information

In April, 2012, the Meteorological Agency has made

a proposal titled “Criteria for issuing tsunami warning

and content of information”. The proposal points out

that there still remain several problems in the content

of conventional tsunami warning and information

given to the general public, and clarified problematic

point and direction for improvement.

(1)Problematic point in tsunami warning and information for

the general public

Followings are the controversial point in tsunami

warning and information disclosure in the Great East

Japan Earthquake of last year.

The first tsunami warning was issued 3 minutes

after the outbreak of earthquake. However, the

magnitude of the quake and height of the tsunami

may be underestimated in the first warning, and

this misleading information led to the delay of

evacuation.

Most of all seismograph indicators went off the

Fig.2 Prevention of parapet collapse (Source: Summary of the report; ”Basic concept for the restoration of coastal levee damaged by the 2011 off the

Pacific coast of Tohoku Earthquake and Tsunami” Coastal Tsunami Countermeasure Investigation Committee, MLIT)


July 2012 No.60

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scale due to inexperienced vibration of magnitude

9. Therefore, magnitude of the quake could not

be calculated within 10 minutes after quake

because the lack of data, Calculation was finished

and magnitude was determined using other

country’s seismographic data after 55 minutes

from the quake vibration.

The first tsunami warning contains the

information of the first wave of tsunami which is

not necessarily higher than waves afterwards, and

some local residents might have judged to stop

evacuation.

(2)Direction for tsunami warning improvement from technical

viewpoint

It is important not to issue underestimated tsunami

warning especially at the first stage of tsunami

warning. From technological point of view,

We need to introduce seismograph that will not

easily go off the scale even in severe environment.

Using the data obtained from cable-type offshore

water pressure gauges, we should quickly update

tsunami warning. And we should modify

tsunami warning based on the observation data of

actual tsunami.

(3) Criteria for issuing tsunami warning and content of

information

The conventional expression and the style of tsunami

warning and the information transmission should be

revised based on the concept; “Receiver can easily

understand tsunami information and warning.”

“Receiver can easily imagine the tsunami height and

can draw a picture of forthcoming damage in mind.”

“Receiver can immediately take action for disaster

prevention.”

Specifically, in order to transmit important

information in easy-to-understand form, we will

improve the methodology of tsunami warning and

information transmission as mentioned below, in

consideration with the accuracy of information and

releasing timing.

① Expression of mentioning tsunami height, in tsunami alert

or warning.

Simple and understandable expression should be

used (1m, 3m, 5m, 10m, over 10m, ). In case of 1

～3m, the higher side figure 3m should be used.

While the size of the quake is not well determined

yet, the expression “high tsunami” or “huge

tsunami” should be used.

Taking example of the past quake or tsunami,

such as “The magnitude with East Japan Quake

class”, we have to transmit estimated images of

abnormal situation.

② Expression to appeal immediate evacuation

In case that the tsunami is generated off the coast

of Japan, we will use the expression of “immediate

evacuation” regardless the length until estimated

time of arrival.

For the tsunami generated off the coast of Japan, its

arrival time varies from several minutes to 1 or 2 hours

from the quake vibration. If the residents judge that

there is a plenty of time to do something and let their

guard down, this might bring serious situations.

③ Expression of geographical warning/evacuation areas and

residents’ action to be taken subjected to disaster

Rough geographical area should be determined in

the early stage, and clear order must be issued on

“Who should evacuate to where”.

The necessary/sufficient and simple wording should be

used, and should clearly indicate who take what action.

For example, “Huge tsunami is coming and serious

damage will occur. People in coastal areas, or in river


July 2012 No.60

16

side, should immediately evacuate to high ground,

evacuation building, or safe locations. Tsunami comes

many times from now on. Stay in the safe place until

tsunami warning is cleared.”

On the other hand, the disaster afflicted area should

not specifically be mentioned at this stage, because

ambiguity still remains depending on the local

geography or land utilization.

Table: Tsunami height and the risk, and actions to be taken

Warning

classifications

Tsunami

height

Tsunami risk Actions to be taken

Huge tsunami warning 10m< Wooden house will collapse and flow

away. People will be swallowed by

tsunami.

People in coastal areas, river side

should immediately evacuate to the

safe areas

5-10m

3-5m

Tsunami warning 1-3m Wooden house will be inundated.

People will be swallowed by tsunami.

People in coastal areas, river side

should immediately evacuate to the

safe areas

Tsunami alert 0.2-1m Swimmers may be washed away.

Farming raft may be washed away.

Small vessel may turn over.

People staying in or close to the sea

should leave the beach.

The above table is made based on the relationships among tsunami height, flood depth, and actual damages, based on the actual tsunami data, caused by the Great East Japan Earthquake in 2011.

④Expression for the estimated arrival time of tsunami

Delay of the tsunami arrival time is a common practice Even in the adjacent forecasting areas, the arrival time

of tsunami may differ more than 1 hour. So this

information should also be transmitted. For example,

“The estimated time of tsunami arrival is the time

when the tsunami reaches to the beach in the earliest

opportunity. So there can be time difference

depending upon local conditions”.

⑤Expression for the priority when we transmit warning to the

wide area

When we issue a warning across the whole country, we

have to emphasize locations exposed to immediate

hazard. In principle, all warnings and alerts should be issued to

every district and information concerning tsunami

height and estimated time of arrival should be

conveyed. However, for such district that may be hit

by tsunami very soon, special emphasis should be

placed with flags and remarks.

⑥Content and expression for the tsunami observation data

Regarding the first wave of tsunami, actually arrived time

will only be announced and no information of tsunami

height should be released.

Observed maximum tsunami height will gradually be

announced If observed low height of first wave information is

released, and then people feel to take it easy, but much

higher second and third wave may coming soon. So

only information of arrived time and type of wave is

announced and no information of tsunami height is

released for the first wave of tsunami observation.


July 2012 No.60

17

4.The law regarding “Construction of

tsunami-resistant society”

When we implement the disaster restoration projects

for quake and tsunami hit areas, a far sighted strategy

is required and promotion of “Construction of

tsunami-resistant society” is required. In order to

prevent or alleviate future tsunami disasters, it is

necessary to build a general and practical system that

can be applicable nationwide, not only disaster hit

areas. To this end, the law regarding “Construction of

tsunami-resistant society” was enacted on December

14th 2011, and that is the multiple defense system

combination of hardware policy and software policy.

According to this law,

(1) Minister of MLIT will lay down basic principles,

(2) Prefectural governor will set up tsunami

inundation assumptions, and make it open to the

public,

(3) Based on the above (1) and (2), local government

will establish promotion plan,

(4) Prefectural governor can nominate “Tsunami

disaster warning district”, and within this warning

district “Special warning zone” is nominated and

land utilization may be restricted.

(5) Prefectural governor and head of local government

will construct, make improvement, and operation

and maintenance of tsunami protection facilities.

(1)Basic principles

Basic principle laid down by the Minister stipulates

the multiple defense system combining hardware policy

and software policy, based on the philosophy, “Even

though the largest class tsunami comes, we will protect

lives of citizens”, based on the experience of the Great

East Japan Earthquake.

(2)Tsunami inundation assumptions

Prefectural governor will set up worst tsunami

inundation assumptions, and implement computer

simulations and specify housing inundation areas and

water depth, and make it open to the public.

(3)Establishment of promotion plan

Local government will establish promotion plan for

“Construction of tsunami-resistant society” based on

the local demand, keeping in mind the above (1) and (2).

And in this promotion plan, the followings are

guidelines.

Local government will effectively combine hardware

project (tsunami protection facilities, evacuation

facilities) and software policy (nomination of tsunami

warning district).

Also with using private facilities, local government will

secure evacuation facilities effectively.

Local government will make tsunami hazard maps and

notify to the residents, and will also implement practical

evacuation drill.

(4)Nomination of “Tsunami disaster warning district”

Prefectural governor can nominate “Tsunami disaster

warning district” for such areas that need to establish

emergency warning and evacuation systems.

Within the above “Tsunami disaster warning districts”,

prefectural governor can nominate “Tsunami disaster

special warning zone”. In this special zone, land use,

development activity and building construction shall be

limited in order to save lives and properties of the people. One of the examples of such restriction in this special

zone is that “The floor of a hospital room or elder care

facility should have a height much greater than the

estimated tsunami height, in order to save lives of

patient”.


July 2012 No.60

18

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