Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanOVERVIEW OF FIRES FOLLOWINGTHE GREAT EAST-JAPAN EARTHQUAKEAi SEKIZAWA1 and Katsunori SASAKI2
1

Professor, Department of Fire Science and Technology, Tokyo University of Science,
Shinjuku, Tokyo, Japan, sekizawa@rs.kagu.tus.ac.jp
2
Research Staff, OYO Corporation,
Tsukuba, Ibaraki, Japan, sasaki-katsunori@oyonet.oyo.co.jp

ABSTRACT: The Great East-Japan Earthquake on March 11, 2011 actually caused
large-scale and wide range fire damage. It may be said that the fire damage was
equivalent or even larger in size and diversity of fire patterns, if comparing to the firedamages in the 1995 Hanshin-Awaji Great Earthquake. Also, this earthquake showed adistinctive feature such that there were quite many fires caused by tsunami directly
and/or indirectly. As many of fires that occurred in the cities and towns, where there arecoastal zone, were more or less affected by the tsunami, so we deemed them as "tsunami
induced-fires" for the sake of convenience in the paper. On the other hand, the fires in thecities and towns, where there are not coastal zone, were not affected by tsunami, so wetreated them as "earthquake-induced fires." Since the mechanism of occurrence of“tsunami-induced fires” differs largely from “earthquake-induced fires,” we think these
two types of fires should be analyzed separately. In this paper, therefore, we describe theoverview of fires following the Great East-Japan Earthquake such as regional distributionof fires and patterns of ignitions of both the above two types of fires. Also presented are
the findings from the results of the analysis on the relation between the incidence of“earthquake-induced fires” and the seismic intensity in comparison with the data in the
1995 Hanshin-Awaji Great Earthquake.
Key Words: Great East-Japan Earthquake, post-earthquake fire, earthquake-induced fires,
tsunami-induced fires, fire cause, fire pattern

INTRODUCTION
The earthquake on March 11, 2011, off the Pacific Coast of Tohoku (referred to as the Great
East-Japan Earthquake below) was a colossal earthquake of a scale estimated to occur once every
1000 years. It caused damage of unimaginable proportions, starting with widespread and large-scaletsunami damage, followed by accidents at a nuclear power plant, the collapse of buildings and the
spread of fire. All told, this disaster left the dead or missing who amount to roughly 20,000.
Although the damage caused by fire was perhaps not comparable with the tsunami and theaccident of the nuclear power plant in terms of ferocity and severity, the fire damage was nonethelesslarge-scale and widespread, and there were a wide range of causes of fire outbreaks. On an absolute883

scale, it can be said that since the Great Kanto Earthquake, the scale and the diversity of fire damage
in this earthquake is comparable only to that in the Great Hanshin-Awaji Earthquake. The
investigation and elucidation of this fire damage is urgently needed, and the obtained knowledge will
be extremely important for developing future fire prevention measures.
For example, aerial images taken by the Japan Air Self-Defense Force showing the scale and theextent of fires in the city of Kesennuma were broadcast on the evening news on the day of theearthquake, and the memory of these images is still fresh. The footage showed oil spilled fromcollapsed oil tanks and ignited in different ways, giving rise to fires (burning piles of wooden debris
and petrol or crude oil floating on top of the tsunami) which ignited buildings along the coast andmountain forests and gradually spread to settlements and urban areas. Further shocking images, whichwere broadcast repeatedly, included burning buildings and debris floating on top of the tsunami as wellas cars burning one after another. In coastal industrial areas, LPG tanks and oil refineries were also
engulfed in flames.
Furthermore, the tsunami was not the only cause of fires. In Tokyo, where the intensity was
between 5-lower and 5-upper in the seismic intensity of JMA (Japan Meteorological Agency) scale, 35
earthquake fires (distinguished from ordinary fires) emerged on that day, and one of the characteristicsof this earthquake was that conventional earthquake fires were numerous despite the limited building
damage. The limited damage can perhaps be explained with the distribution of the peak ground
velocity, which is related to building damage. On the other hand, even if fires are not caused directlyby the collapse of buildings, they can still emerge from upturned and fallen objects inside buildings, aswell as from the failure of external lifelines (power lines, gas pipes, etc.), and therefore the cause offires is not limited to the collapse of buildings. The building collapse ratio has been used as analternative index of earthquake strength. However, even though there is a well-established correlation
between the building collapse ratio and the fire outbreak rate, a causal relation between the two factors
has not been confirmed. Therefore, to avoid widespread misunderstanding in the future, it is necessary
to investigate a predictive model of fire outbreaks based on the seismic intensity index itself rather
than on the relation between building collapse ratio and fire outbreak ratio.
Accordingly, this report first outlines the overall aspects of earthquake fires that emerged in the
Great East-Japan Earthquake; then, these fires are separated into "tsunami-induced fires", whichdisplayed distinct characteristics in this earthquake, and the well-known conventional"earthquake-induced fires", and important points about each type are mentioned.

EARTHUAKE-INDUCED FIRES AND TSUNAMI-INDUCED FIRES
Fig.1 shows a map with the locations of earthquake fires caused by the Great East-Japan Earthquake,
which was prepared on the basis of the "Great East-Japan Earthquake report" issued by the Fire andDisaster Management Agency. Although some of the numbers given here are slightly different fromthose in the report, they were taken from data provided by local fire departments and it is unlikely that
this affects the overall trend.
In Fig.1, circles in light gray represent the location of fires in the municipalities that suffereddamage in the coastal area highlighted in Fig.2. A large number of these locations were affected in
one way or another by the tsunami, and therefore in this report they are considered separately as socalled tsunami fires (referred to as "tsunami-induced fires" below). There is a possibility that thiscategory includes some conventional earthquake fires caused directly by the earthquake, such as firesin oil and gas tanks. We ask for understanding regarding such cases because, with the information
gathered up to now, such fires cannot be distinguished from true tsunami-induced fires. However,tsunami-induced fires are considered separately from earthquake-induced fires for the city of Sendai
since a clear distinction can be made in this case. On the other hand, circles in black indicate fires inmunicipalities which were not affected by the tsunami, in other words, they indicate known types ofearthquake fires (referred to as "earthquake-induced fires" below).

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Fires up to March 21
Total number of fires:
287
Note: According to the“Earthquake off the
Pacific Coast of
Tohoku” report by theFire and Disaster
Management Agency

Fig.1 Fire outbreaks following the Great East
Japan Earthquake.

Fig.2 Damaged municipalities along the coast.

The purpose of this endeavor is to analyze the relation between earthquake intensity (parameterssuch as seismic intensity and building collapse ratio) and the outbreak of fires. In performing acomparison with fires in previous earthquakes, earthquake-induced fires must be distinguished fromtsunami-induced fires, which differ in terms of outbreak mechanism and counting, and therefore only
the former type should be taken into account. Furthermore, the outbreak of extensive tsunami-induced
fires in a number of areas, as well as the expansion of some of them into large-scale fires, must be
investigated independently on the basis of information gathered through on-site surveys, witness
accounts and numerous images. At present, material from various surveys has been processed andanalyzed, and a concise description of this data is provided below.

RATIOS OF BUILDING COLLAPSE AND FIRE OUTBREAK
WITH SEISMIC INTENSITY FOR EARTHUAKE-INDUCED FIRES
Here, we discuss the relation between the seismic intensity, the building collapse ratio and the fire
outbreak rate with respect to the 126 instances of earthquake-induced fires, which are marked withblack circles in Fig.1. In the Great Hanshin-Awaji Earthquake, the total number of fully collapsedbuildings in the city of Kobe was about 67,000, amounting to 4,400 per 100,000 people (thepopulation of Kobe at that time was about 1,520,000). In surveying fire-induced damage in the Great
East-Japan Earthquake, a meaningful comparison can be made with fire-induced damage in the Great
Hanshin-Awaji Earthquake. However, it is necessary to keep in mind the fact that at the time of theGreat Hanshin-Awaji Earthquake, the seismic intensity in many disaster areas in Kobe was 7, while inthe current case the intensity in most disaster areas was 6-upper or less.
Fig.3 shows the building collapse ratio plotted versus seismic intensity. In areas where the intensity
in the Great East-Japan Earthquake was 6-upper, even if half of the semi-collapsed buildings are added
to the number of fully collapsed buildings, the total number still amounts to only 523 per 100,000885people, which is about one order of magnitude lower than the abovementioned figure for Kobe. Also,
there are almost no collapsed buildings in areas where the intensity was 5-upper or less. However, thecorrelation between seismic intensity and building damage is tentative.
On the other hand, Fig.4 shows the fire outbreak rate versus seismic intensity, and it can be seenthat for areas with intensity of 6-upper, the fire outbreak rate is rather low at 0.65 per 100,000 people,
with the highest fire outbreak rate being 1.00 per 100,000 in areas with seismic intensity of 6-lower.
This is also one order of magnitude lower than the fire outbreak rate in the Great Hanshin-Awaji
Earthquake, where the 175 instances of fire amounted to a rate of about 11.5 per 100,000 people. In
consequence, in areas where the intensity was 6-lower for example, the number of fires versus
thousand of collapsed buildings in the Great East-Japan Earthquake, which is 2.6, was quite similar tothat for the Great Hanshin-Awaji Earthquake, which is 2.1, which leaves the question why the building
damage was so limited in the Great East-Japan Earthquake to compare with that in the Great
Hanshin-Awaji Earthquake.

600
500

Building Collapse ratio: (Number of fully
collapsed buildings + number of semi-collapsedbuildings/2) per 100,000 people
522.8
487.5

1.4

Fire outbreak rate: Number of outbreaks per
100,000 people
1.20

1.2
1.0

400

0.84

0.8
300

0.6

200

0.35

0.4

100
0.2

4.1

0.24

0.2

38.5

0.0

0
up to 4 5-lower 5-upper 6-lower
Seimic Intensity in JMA scale

up to 4

6-upperFig.3 Building collapse ratio versus seismic intensity.

800

5-lower 5-upper 6-lower 6-upper
Seimic Intensity in JMA scale

Fig.4 Fire outbreak rate versus seismic intensity.

Building collapse ratio: (Number of fully collapsedbuildings + number of semi-collapsed buildings/2) per
100,000 people

Fire outbreak rate: Number of outbreaks
per 100,000 people
1.4

725.1

700

1.26

1.25

1.2

600

1.0

500

0.6

300

174.1 202.1

200
97.8
0.3

18.7

2.0

100

200

300

0.73

0.8

365.9

400

100

0.71

0.49
0.32

0.4

69.5

0.2

0

0.28

0.26

0.28

400

500

600

0.14

0.0
400

500

600

700

800 900～

100

Fig.5 Building collapse ratio versus Peak GroundAcceleration.

200

300

700

800 900～

PGA (gal)

PGA (gal)Fig.6 Fire outbreak rate versus Peak Ground Acceleration..

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Fig.5 shows the building collapse ratio plotted versus peak ground acceleration (hereinafter called
PGA). To compare with the relation between the building collapses ratios and the seismic intensity, aclear correlation is seen between the building collapse ratio and PGA. As PGA increases above
700(gal), the number of collapsed buildings per 100,000 people steeply grows and reaches 725 at
900(gal) if including the number of a half of the semi-collapsed buildings.
On the other hand, the correlation between the fire outbreak rates versus PGA in Fig.6 is not asclear as that seen between the building collapse ratio and PGA in Fig5. However, if comparing withthe relation between the fire outbreak rates versus seismic intensity, the correlation between the fire
outbreak rates and PGA is obviously seen. And, the fire outbreak rate grows drastically if PGA
exceeds 700(gal). The impact of PGA on both the building collapse ratio and the fire outbreak rateshould be investigated in more detail in the future work.
The characteristics of the Great East-Japan Earthquake in comparison with the Great
Hanshin-Awaji Earthquake can be understood by looking at the building collapse ratio and the fire
outbreak rate plotted in Fig.7 and Fig.8. A correlation between the building collapse ratio and the fire
outbreak rate is difficult to derive for the Great East-Japan Earthquake in Fig.7, and in any case bothparameters are low for areas where the seismic intensity was below 5-lower. On the other hand, for the
Hanshin-Awaji Earthquake, there is a clear relation between the building collapse ratio and the fire
outbreak rate seen in Fig.8, and the values for both parameters are high. Furthermore, Fig.9 shows acomparison of the building collapse ratio and the fire outbreak rate for each municipality where
earthquake-induced fires emerged. The fire outbreak rate is high in areas where the building collapse
ratio is low, and vice versa.

1.20

Incidence of post-earthquake fires(# of ignitions by 7:00 a.m. per 100, 000 households

Fire outbreak rate: Number of outbreaks per 100,000 people
1.40
Seismic intensity 4

1.00
Seismic intensity 6-lower
0.80
0.60

Seismic intensity 6-upper

0.40
Seismic intensity 5-lower
0.20

Seismic intensity 5-upper

0.00
0

100

200

300

400

500

30

Nada Nagat a
As hiyaHy ogo20

Ch uohHigashin ada
Su ma

10

Itami
A magasaki
Nishi
Kita Tarumi

0
0

600

Nis hino miys

10

20

30

Ratio of damaged structures(%: razed structures/totalstructures)

Building Collapse ratio: (Number of fully collapsed buildings +number of semi-collapsed buildings/2) per 100,000 people

Fig.8 Relation between the ratio of fully
collapsed buildings and the rate of fire outbreaks
immediately following the earthquake (data for
the Great Hanshin-Awaji Earthquake)

Fig. 7 Relation between building collapse ratio
and fire outbreak rate in accordance withearthquake intensity.

One conclusion that can be drawn from the Great East-Japan Earthquake is that there is no directcausal relation between building damage (such as of the ratio of fully collapsed to semi-collapsedbuildings) and earthquake fires. Also, although modern buildings might not collapse, flammableobjects located above utilities producing fire inside the buildings might be upturned or otherwise
affected by the earthquake. Furthermore, lifeline systems such as power lines and gas pipes can bedamaged by seismic motion, and fires might break out after the power supply has been restored. In thissense, in addition to avoiding the commonly held but mistaken notion that "fire outbreaks are related
to the collapse of buildings", it is necessary to replace the conventional fire prediction model based on
the relation between building collapse ratio and fire outbreak ratio with a new fire prediction model
considering the mechanism according to which fires break out after earthquakes.

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Fig. 9 Regional distribution of Building collapse ratio and Fire outbreak rate by municipality forearthquake-induced fires.

TSUNAMI-INDUCED FIRESThe Great East-Japan Earthquake induced a tsunami that inflicted severe damage on municipalities
located in an area ranging from Iwate and Miyagi prefectures along the Sanriku coast to Fukushima,
Ibaraki and Chiba prefectures. A large number of fires emerged in some of the municipalities in Iwate
and Miyagi prefectures near the Pacific Ocean immediately after the direct damage inflicted by thetsunami, and several of those fires expanded into full-fledged urban fires. Tsunami-induced fires,shocking footage of which was broadcast on TV, were characteristic phenomena in the Great
East-Japan Earthquake.
The causes of many of the fires in the municipalities along the coast shown in Fig.2 were related tothe tsunami. Although these fires are referred to as tsunami-induced fires in this report, the provided
numbers also include conventional earthquake fires caused directly by the earthquake, such as fires inoil and gas tanks. Although the complete picture of tsunami-induced fires is still unclear, theinvestigations have been undertaken by the various universities and laboratories. The obtained
information is continuously disseminated, creating an environment of research collaboration in theform of information sharing between researchers, as well as between institutions, from the very
beginning of the disaster, which is unprecedented in the field of fire research. The development anduse of modern communication technology, such as the Internet and GPS, have played a major role inrealizing such collaboration.
The overall picture of tsunami-induced fires will be discussed in future work, and the discussion inthis report will be limited to a concise description of the outbreak pattern of tsunami-induced fires.
Based on the information about fires available to the authors, various conditions can be pointed out as
causes of tsunami fire outbreak.

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(1) Spillage, ignition and flow of oil or LPG from upturned or collapsed storage tanks in industrial
areas, and subsequent ignition of urban areas and buildings(2) Spillage from upturned kerosene tanks and LPG cylinders in residential buildings, or spillage frombroken distribution pipes(3) Ignition of buildings by burning buildings or debris carried by the tsunami(4) Ignition of buildings by burning ships or cars carried by the tsunami(5) Acceleration of the oxidation of iron by salt contained in seawater, resulting in spontaneous
ignition from heat trapped in mounds of debris containing ironBy the way, four fires emerged after the tsunami which devastated the Aonae area on the island of
Okushiri following the 1993 earthquake off the southwest coast of Hokkaido. Two of these fires brokeout on harbored ships, one building fire broke out in the urban area after the tsunami, and the fourthfire broke out in the inundated area from an unknown ignition source. The latter two were the sourcesof urban fires in Aonae as seen in Fig.10.
At the time, we surveyed the fire in Aonae on the island of Okushiri, but the causes of thetsunami-induced fires remained unclear. However, after witnessing the large number of fires that brokeout throughout several prefectures as a result of the tsunami following the Great East-Japan
Earthquake, it was strongly felt that the fires in Aonae were the manifestation of a universal
phenomenon occurring after a tsunami rather than isolated events.
Difficulties associated with fire fighting activities should also be mentioned in regard totsunami-induced fires. Naturally, the initial response is difficult due to evacuation. In addition, large
amounts of debris block roads not only during, but also after the tsunami, thus obstructing the passage
of fire engines and firefighters. Also, fire hydrants might become unusable due to damaged lifelines,
which further obstructs fire fighting operations.
There are a number of other factors that play a role in the ignition and spread of tsunami-induced
fires and the obstruction of fire fighting operations. Future measures for fire prevention and damage
mitigation should be developed by making progress in surveys and research, as well as by elucidating
all aspects and problems associated with tsunami-induced fires.

The
first fire
第1の火災

The
second fire
第2の火災

Tsunami-induced fires
Ship
fire
船の火災

Ship
fire
船の火災

Fig.10 Post-earthquake fires after the South-West off Hokkaido
図10
奥尻島青苗地区の火災の出火点と延焼動態（文献１）より）at Okushiri
island in 1993.

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CONCLUSIONS: PROBLEMS TO BE INVESTIGATED IN FUTURE STUDIESThis report presents a summary based on a broad collection of materials, such as the surveys byourselves, information published other researchers, articles and photographs from newspapers andmagazines, news broadcasts and footage found on the Internet. The volume of written material, articles,
photographs, footage and graphs is immense, and it is impossible to present all of it within the limited
space available for this report. Therefore, an attempt was made to present a concise overview of the
aspects and the characteristics of earthquake fires following the Great East-Japan Earthquake. Due tothe limited time, this report inevitably contains inconsistencies and incomplete parts, and we ask forunderstanding in regard to such issues. By further advancing surveys and analysis in the future, weplan to develop and deepen our understanding on the subject while ensuring good accuracy.
Instead of a summary, the problems that should be investigated in future surveys and studies on
earthquake fires are outlined below.
(1) Surveys and compilation of a database on earthquake fires and related information for eachmunicipality.
(2) Analysis of case studies on tsunami-induced fires, analysis of the patterns of ignition and burning,elucidation of outbreak mechanisms and development of damage mitigation measures.
(3) Surveys on fires in factories in industrial areas, and elucidation of the causes of outbreaks,
prevention measures.
(4) Elucidation of the outbreak mechanisms for earthquake-induced fires and development of a new
prediction model for the fire outbreak rate.
(5) Investigation of fire outbreaks following the restoration of power supply (e.g., the relation between
the time of power restoration and the times of fire outbreaks).
(6) The status of fire fighting activities, problems with acquisition and communication of disaster
information, damaged fire hydrants and roads, and other obstacles impeding fire fighting activities.
(7) Investigation of the influence of sprinklers, fire alarms, fire doors and other fire safety equipment,
as well as investigation of damage incurred by such facilities.

ACKNOWLEDGMENTS
The authors acknowledge the contributions from Prof. Takeyoshi Tanaka at Kyoto University, Prof.
Tokiyoshi Yamada, Assistant Prof. Hiroi Yu, and Mr. Noriaki Sakamoto at University of Tokyo who
conducted parallel surveys with us on fire damage investigations. We are also indebted to Ms. Ayaka
Tobari, Mr. Taichi Yamamura and Mr. Kohei Fujii (graduate students at the Graduate School of Global
Fire Science and Technology, Tokyo University of Science) for their contribution in compiling thematerial and preparing the data for this report.

REFERENCES
Zama, S., Sekizawa, A.(1993). “The 1993 Southwest-off Hokkaido Earthquake and ensuing damage”,
Shoken Shuho (Journal of National Research Institute of Fire and Disaster), No 47, 3-11.

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