Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanA COMPARATIVE STUDYON PEOPLE’S AWARENESS OF EARTHQUAKEEARLY WARNING BEFORE AND AFTER
THE 2011 GREAT EAST JAPAN EARTHQUAKE
Miho OHARA 1, Kimiro MEGURO 2 and Andrew Atsushi TANAKA 3
1

Associate Professor, Interfaculty Initiative in Information Studies/ Institute of Industrial Science,
The University of Tokyo, Japan, ohara@iis.u-tokyo.ac.jp
2Professor, Interfaculty Initiative in Information Studies/ Institute of Industrial Science,
The University of Tokyo, Japan
3Professor, Interfaculty Initiative in Information Studies,
The University of Tokyo, Japan

ABSTRACT: After the Great East Japan Earthquake on March 11, 2011, Earthquake
Early Warning (EEW) was frequently provided. However, some of the warning ataftershocks failed to estimate intensity properly due to technical limitation. In this paper,
questionnaire surveys were conducted to understand people’s awareness of EEW before
and after the Great East Japan Earthquake and change of their awareness was analyzed
comparing both results. Their behavior after receiving the warning was also analyzed andsuggestions for enhancing their capacity to take proper actions after EEW were obtained.
Key Words: Great East Japan earthquake, early warning, people’s awareness, capacity
building, questionnaire survey

INTRODUCTION
The Japan Meteorological Agency (JMA) began to provide the service of earthquake early warning(EEW) to the public on October 1, 2007. This is a new system that quickly analyses seismic wave data
observed by seismographs near the epicenter and provides prompt alerts before the arrival of strong
tremors (S-waves) as shown in fig.1. For public use, EEW is provided to the regions where theintensity of shaking was expected to be greater than JMA 4 in case the maximum estimated intensity is5 lower. This system aims to mitigate earthquake-related damage by enabling individuals to protect
themselves quickly in various environments such as houses, offices and factories. A warning is widely
broadcasted by television, radio, mobile phone and loudspeakers.
The Iwate-Miyagi Inland Earthquake occurred in the southern inland region of Iwate Prefecture,
Japan at 8:43 JST, June 14, 2008. It was the first earthquake since October 2007 for which EEW could
be successfully broadcasted before the arrival of strong tremors. The lead time between the warning

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and the arrival of strong tremors was around 10-25 seconds in the area surrounding its epicenter. After
this, a small earthquake occurred in Fukushima Prefecture at 16:59 JST on September 29, 2010. EEW
was broadcasted in the eastern area of Japan as the expected intensity exceeded 4. It was broadcasted
also in the Tokyo metropolitan area although observed intensity was less than 4. Recently, thepercentage of the people who can get EEW by mobile phones is increasing. At this earthquake, a lot ofpeople received the warning by mobile phone in the Tokyo metropolitan area for the first time and it
became a good opportunity for making people familiar with EEW.
The 2011 off the Pacific coast of Tohoku Earthquake occurred at 14:46 JST on March 11, 2011
and numerous aftershocks continued. EEW was successfully provided in Tohoku area at the mainshocks. On the other hand, in the Tokyo metropolitan area, EEW failed at the main shock but wasfrequently announced at aftershocks. The number of broadcasted EEW from March 2011 to August2011(6 months) was 87 although that number from October 2007 to February 2011(41 months) was 17.
However, some of the numerous warning at aftershocks failed to estimate intensity properly because
several earthquakes occurred at the same time could not be identified separately or some seismometers
were unusable due to long-time power outage after the earthquake. These problems were due totechnical limitation of EEW and some of them were solved by program modification after March2011.
In this paper, two questionnaire surveys were conducted to understand people’s awareness ofEEW. The first one was done after the earthquake in September 2010 for the people who received thewarning by mobile phone. The second one was done after the earthquake in Tohoku region in March
2011. The change of their awareness was analyzed comparing both results. Their behavior after
receiving the warning was also analyzed and suggestions for enhancing their capacity to take proper
actions after EEW were obtained.
Transmit observed data

S-waveP-waveInform of the coming tremorsbefore their arrival

S-waveSeismograph

Focus

Focus

When P-wave was observed

When S-wave arrived

Fig. 1 Concept of Earthquake Early Warning

OUTLINE OF TWO QUESTIONNAIRE SURVEYS
The first questionnaire survey was done after the earthquake in Fukushima Prefecture on
September 29, 2010. Main target of the survey was the people living in the Tokyo Metropolitan area
(Tokyo, Saitama, Chiba, Kanagawa Prefectures) who received the warning by their own mobile phoneor neighbor’s mobile phones. The number of respondents in each group was shown in table 1. The
second survey was done after the earthquake in Tohoku region in March 2011. A questionnaire sheet
was sent to the same respondent as the first survey. The ratio of the respondents who answered thesecond survey was 76.6％(613 people among 800). The number of the group A respondents whoanswered the survey in 2011 was 153. Among them, 11 people changed their mobile phones and could
not receive EEW as of March 2011. The number of the respondents in each group who answered thesurvey in 2011 and could receive EEW as of March 2011 was shown in table 1.

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Table 1 Number of respondents for surveys in 2010 and 2011
2011 Survey
Ratio of theCould receive EEW by mobile phone
Could notrespondents
as of March 2011
receive EEW
who answeredby mobile
total
Received at Received outside
the secondphoneasof
home after
home aftersurvey
March 2011
march 2011 march 20112010 Survey

Received EEW by their own mobilephones
Received EEW by their neighbors'Bmobile phones
Received EEW by their own mobile
C phones and experienced the stopof train
D Didn't receive or listen EEWA20014211891

11153

76.5200

7048428115175.52001196552311507520071493688159

79.5

RESPONDENTS’ KNOWLEDGE OF EARTHQUAKE EARLY WARNING
At first, change of respondents’ knowledge of EEW was analyzed comparing the results of twosurveys. All the groups had the same tendency between 2010 and 2011. Figure 2 shows the result ofgroup A for example. After the earthquake in September 2010, 50.3% knew both the name of EEW
and that it forecast a strong tremor just before its arrival. After the experience of the main shock andaftershocks of Tohoku earthquake in 2011, the ratio increased to be 89.5%. At the survey in 2011, therespondents who knew neither its name nor its meaning were drastically decreased to be 2.0%.
100%31323I knew neither its
name nor itsmeaning
I knew only thename of EEW

80%
60%

53
137

40%
20%

77

I knew goth thename of EEW andits meaning

0%
2010

2011

Fig. 2 Respondents’ knowledge of EEW
EEW cannot be provied before strong tremorsin
the area where is too close to the hypocenters

92.2

73.2

Special receiving devices can show expected
intensity and lead time34.6
30.1

Trains stop after receiving EEW

73.9
71.9

EEW is annoounced in some facilities such as
department stores

33.3

45.1

EEW can be received by mobile phones

96.7

71.2
Lead time is not shown on TV
39.2
Expected intensity is not shown on TV
On TV, the name of the dangerous and warning
messageare shown

92.8

65.4
20.9

EEW is proveded on TV in case maximum
expected intensity is 5 lower

23.50102030

2010

66.0

20.3

EEW is proveded on TV to the area where expected
intensity is 42011
81.0

33.3
39.9
405060708090 100Fig. 3 Respondents’ knowledge of methods or conditions of EEW broadcasting1706

Figure 3 shows the respondents’ knowledge of methods or conditions of EEW broadcasting. It is a
result of group A for example as all the groups had the same tendency between 2010 and 2011. The
ratio of the respondents who knew that EEW is broadcasted on TV or by mobile phone increased after
2010 and exceeded 90% in 2011. On TV, the name of the area where strong tremors are expected andthe warning message are shown. On the other hand, neither expected intensity nor lead time before thearrival of strong tremors is explained. The knowledge on expected intensity or lead time was low in2010 but increased especially in 2011. However, knowledge of criteria on intensity at which EEW is
broadcasted was still low. In addition, change in the knowledge of special receiving devices was verysmall although the special receiving devices are important tools for receiving expected intensity orlead time at home. Enhancing these knowledges is necessary.

RESPONDENTS’ ATTITUDE TOWARD FAILURE OF EARTHQUAKE EARLY WARNING
After the earthquake on March 11, 2011, numerous EEW was provided to the public due to continuous
aftershocks. However, some of them failed to estimate intensity properly because several earthquakes
at the same time could not be identified separately or some seismometers were unusable due tolong-time power outage after the earthquake. These problems were due to technical limitation of EEW
and were announced beforehand by Japan Meteorological Agency. Here, the knowledge of technicallimitation before the earthquake and their attitude toward the failure of EEW were analyzed. 36.5% of
the respondents among all knew the technical limitation before March 2011 that actual intensity can be
more or less than the expected intensity within the range of intensity 1. About 90% of the respondents
wished to use EEW even if it has a risk of failure regardless of whether they knew technical limitation
before the earthquake or not. 55.4% of the respondents with the knowledge of technical limitation
answered that they would like to use EEW aggressively even if they have a risk of failure. The ratiodecreased to be 35.0% without the knowledge. It was verified that familiarization with technicallimitation before the event is important in order to increase positive attitude in case that EEW fails.
100%

0.0
2.7

90%
80%

4.4
8.5

40.6

70%
51.9

60%
50%
40%
30%

55.4

20%

35.0

10%
0%
With Knowledge

I don't have an interest
on EEW
I would not like to use
EEW at all becase of arisk of failure
I would not like to use
EEW becase of a risk offailure
I would like to use EEW
even if it has a risk offailure
I would like to use EEW
aggressively even if it
has a risk of failure

Without Knowledge

Fig. 4 Respondents’ attitude toward failure of EEWRESPONDENTS’ RESPONSE TO EARTHQUAKE EARLY WARNING
Next, respondents’ response to EEW after EEW was investigated. More than 80% of each groupwatched EEW on TV at home after March 2011. The ratio of the respondents who received EEW at
home was highest in group A. 88.4% of group A watched EEW on TV and 80.3% received by mobilephone at home. 59.4% received by mobile phone outside home. The feeling of respondents in group A
after receiving EEW at home was investigated. Figure 5 is the comparison of their feeling after1707

earthquakes in 2010 and 2011. The ratio of the respondents who thought that strong tremor would
come soon drastically increased from 34% to 86.7%. It shows that experience of receiving many EEW
after March 2011 led to high awareness of warning message.
100%
90%

0.7
5.6
8.4

4.6
6.5

I thought it is due to thefailure of a mobilephones

80%
70%
60%

I thought it is a flash
news of earthquakeintensity

45.150%I could not understandthe meaning quickly

86.7

40%
30%
20%

I thought strong tremor
will come soon

34.0

10%
0%
2010

2011

Fig. 5 Respondents’ feeling after receiving EEWFigure 6 shows what respondents in group A did immediately after receiving EEW at home at theboth earthquakes. Most frequent response after both earthquakes was to get earthquake informationfrom television or radio. The second one was to wait and the third one was to inform their children orpeople near them of the EEW. The ratio of the response for informing their children or people nearthem, protect their bodies, protect their children or elderly family members increased in 2011. The aimof EEW service is to enable residents to quickly protect themselves before the arrival of strong tremors.
Considering this aim, it is said the experiences of receiving many EEW after March 2011enhanced
their capacity to take actions for protecting themselves or family members.
I don't remember

1

I could not do anything

1

Others1

I went outside the house or building

1

518
3
3

I opend a door or window248I informed children or others of EEW

34

12I protected children or elderly people
I hide in a safe place and protect my body

2011154201022

4I held furniture or valuables

13

1I put out fire27

8I waited and evaluated the situation

49

39I got information from TV or radio

66

420

102030

40

50

60

70

80

90100Fig. 6 Respondent’s action after receiving EEW

RESPONDENTS’ OPINION ON EFFECTIVENESS OF EARTHQUAKE EARLY WARNING
Finally, their opinion on effectiveness of EEW was investigated. The ratio of the respondents who1708

thought EEW was very effective for mitigating seismic damage was about 40% at the both survey in2010 and 2011. Including the respondents who thought it is effective, the total ratio of positive
respondents amounted to be about 90%. When we focused on the relationship between their opinion
and the experience of receiving EEW after March 2011, the ratio of the respondents who thought to bevery effective was 38.5% as shown in fig.7. It was verified that real experience of receiving EEWenhanced the understanding of effectiveness of EEW. Figure 8 is the relationship between theiropinion and the knowledge on technical limitation before the earthquakes. In the chapter four, wefound that familiarization with technical limitation before the event increased positive attitude toward
the failure of EEW. In fig. 8, the ratio of the respondents who thought to be very effective was 54.5%
in case they had knowledge on technical limitation before the earthquake. This value was almost twiceof the ratio in case of respondents without the knowledge. It is concluded that making people familiar
with technical limitation led to their positive attitude toward EEW and it can increase high evaluationon the effectiveness of EEW
100%
90%
80%70%60%
50%
40%
30%
20%
10%
0%

0.2
7.2

5.7
5.7

54.1
68.6

Not Effective at all
Not Effective
Effective
Very Effective

38.5
20.0
I received EEW

I didn't receive
EEW

Fig. 7 Relationship between understanding of effectivenessand the experience of receiving EEW
100%
90%
80%70%
60%
50%
40%
30%
20%
10%0%

0.0
3.6

2.1
9.3

42.0
60.9

Not Effective at all
Not EffectiveEffective

54.5
27.8
I knew technicallimitation

Very Effective

I didn't know
technical
limitation

Fig. 8 Relationship between understanding of effectivenessand the knowledge on technical limitation

CONCLUSIONSIn this paper, two questionnaire surveys were conducted to understand people’s awareness of EEW.
The first one was done after the earthquake in September 2010 for the people who received thewarning by mobile phone. The second one was done after the earthquake in Tohoku in March 2011.
The change of their awareness was analyzed comparing both results.

1709After the experience of the main shock and aftershocks of Tohoku earthquake in 2011, knowledgeof EEW among residents drastically increased. Some of the knowledges were low still in 2011 andrequired to be enhanced. Their behavior after receiving the warning was also analyzed. The ratio of therespondents who thought that strong tremor would come soon drastically increased from 34% in 2010
to 86.7% in 2011. It shows that experience of receiving many EEW after March 2011 led to highawareness of warning message. In 2011, the ratio of the response for informing their children orpeople near them, protect their bodies, protect their children or elderly family members increased,compared with the answers in 2010. The experiences of receiving many EEW after March
2011enhanced their capacity to take actions for protecting themselves or family members. People’sawareness level and capacity can decrease easily as time passes after the disaster. It is very importantto keep their awareness level by education or training in the future.
After the earthquake on March 11, 2011, numerous EEW was provided to the public due tocontinuous aftershocks. However, some of them failed to estimate intensity properly due to technicallimitation. From the survey, familiarization with technical limitation before the earthquakes increased
positive attitude in case that EEW failed. It also increased high evaluation of the effectiveness of EEW.
Continuous information dissemination on technical limitation is important for positive attitude fortaking action after receiving EEW.

REFERENCES
The Japan Meteorological Agency: “A List of Past Earthquake Early Warning”,
Website: http://www.seisvol.kishou.go.jp/eq/EEW/kaisetsu/joho/joho.html
The Japan Meteorological Agency. (2011). “Earthquake Early Warning provided after the 2011 off thePacific coast of Tohoku Earthquake”, JMA News Release, 2011.3.29.
The Japan Meteorological Agency. (2011). “Improvement of Earthquake Early Warning”, JMA News
Release, 2011.8.10.

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