7f-0004

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020
Paper N°C001751
Registration Code: A01788

THE 2016 KUMAMOTO EARTHQUAKES’ INFLUENCE ON RESIDENTS’RISK PERCEPTION
S. Ohtomo(1), R. Kimura(2), N. Hirata(3)(1) Associate Professor, Konan Women's University, e-mail: s.ohtomo@konan-wu.ac.jp(2) Professor, University of Hyogo, e-mail: rkimura@shse.u-hyogo.ac.jp(3) Professor, the University of Tokyo, e-mail: hirata@eri.u-tokyo.ac.jp

Abstract
The magnitude 6.2 foreshock on the 14th of April and the magnitude 7.3 main shock on the 16th of April occurredin the 2016 Kumamoto Earthquakes. The main shock over than the magnitude 6.2 was not anticipated because theforeshock was considered to be the main shock. The successive two large shocks increased physical damage but also
affected the Japanese risk perception of earthquakes. After the earthquakes occurred, the Japan Meteorological Agency
discontinued its policy of announcing the probability of aftershock occurrences. The experience of the 2016 Kumamoto
earthquakes and the policy changed concerning risk communication may affect the public risk perception of earthquakes.
The study investigates the factors that affected the post-earthquake risk perception. We assumed that the experience of
housing damage caused by the earthquakes, pre-earthquake awareness of local faults, and demographics were related tothe post-earthquake risk perception.
The study used research data from a mail survey implemented by the Ministry of Education, Culture, Sports,
Science and Technology (MEXT) from November 28 to December 19, 2016. Respondents were those who lived in 14
municipalities where the 2016 Kumamoto earthquakes caused severe damage. The number of valid responses wasreceived 3772 (a valid response rate of 46.7%). Male and female valid respondents accounted for 45% and 55%,
respectively. The average respondent age was 53.24 (SD = 16.20). The study analyzed data of pre-earthquake awarenessof local faults, housing damage (completely destroyed, half-destroyed, partially destroyed, no damage), risk perceptionof earthquakes (severity, knowledge, uncertainty), and demographics (gender, age).
The study implemented Bayesian generalized linear model analyses to reveal the differences in post-earthquake
risk perception between pre-earthquake awareness of local faults, housing damage, and demographics. First, the postearthquake perception of the severity of earthquakes differed by housing damage. People with completely destroyed andhalf-destroyed households perceived severity more than people with partially destroyed households and no damage.
Second, the main effects of pre-earthquake awareness of local faults, gender, age, and the interaction effect of preearthquake awareness × gender on the post-earthquake perception of knowledge of earthquakes were found. Especially,
for those with the awareness of local faults, males had more post-earthquake perception knowledge than females, whereas
for those without the awareness, females had more post-earthquake perception knowledge than males. Moreover, there
was no difference in the post-earthquake perception of the uncertainty of earthquakes between housing damage,demographics, and awareness of local faults.
The study suggested that the three aspects of risk perception of earthquakes were formed by different factors. The
perception of severity could be updated by experience suffering from earthquakes. The perception of knowledge could
be dependent on demographics and how aware people are of earthquakes. The perception of uncertainty could be formed
by intuition, instead of experience and prior awareness of earthquakes. The study discusses the importance of risk
communication of earthquakes based on human cognitive mechanisms.
Keywords: awareness of local faults, housing damage, Kumamoto earthquakes, risk communication, risk perception© The 17th World Conference on Earthquake Engineering- 7f-0004 -7f-0004

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

1. Introduction
The 2016 Kumamoto earthquake was a magnitude 6.2 foreshock and 7.3 mainshock that occurred on
April 14 and 16, 2016, respectively. The latter 7.3 shock was not anticipated by most residents because the 6.2
foreshock was considered to be the mainshock at the time. According to the Cabinet Office [1], 270 deaths
were reported due to the earthquake in Kumamoto prefecture. Housing damage reports indicated that there
were 8,657 completely destroyed, 34,491 half-destroyed, and 155,095 partially destroyed houses. In addition
to this serious damage, the two large consecutive earthquakes caused unexpected reactions and actions fromresidents [2]. For example, different reasons were given with respect to the residents’ decisions made during
the foreshock and mainshock evacuations. The residents’ evacuation patterns influenced the subsequent risk
perception of earthquakes. Moreover, the residents' pre-earthquake awareness of local faults was found to
relate to their anticipation of aftershock occurrences after the foreshock and mainshock [3]. However, themanner in which residents’ experience of the 2016 Kumamoto earthquake impacted their risk perception ofearthquakes given their pre-earthquake awareness of local faults is yet to be studied.
Empirical studies in risk perception research aim to examine the psychological process of cognition ofrisk. According to Slovic [4], risk perception is based on subjective aspects such as “dread” and the “unknown.”
In addition, risk perception has been considered to be based on two-thinking systems: the first system involves
experiential decision-making based on affective experience and intuition (System 1), whereas the second
system involves analytic decision-making based on knowledge and rationality (System 2) [5]. Furthermore, areview of risk perception studies of natural hazards has indicated that risk perception can be determined byboth direct experience (e.g., experiencing a hazard oneself) and indirect experience (e.g., education and media)[6]. Based on these two-thinking systems, being a victim of an earthquake of can be considered a factor ofexperiential decision-making of System 1 and one’s knowledge of earthquakes can be considered a factor ofanalytic decision-making of System 2. Moreover, previous studies have indicated that risk perception can be
influenced by personal factors such as gender and belief [7, 8]. The present study aims to examine how
respondents’ experience of housing damage (System 1 factor), pre-earthquake awareness of local faults(System 2 factor), and demographic factors (gender and age) influenced their risk perception after the
Kumamoto earthquake.

2. Method
2.1. Survey data
The research data included in the present study was from the “Questionnaire survey and analysis on
effect of aftershock information and evacuation actions during the 2016 Kumamoto earthquake,” conductedby the Ministry of Education, Culture, Sports, Science and Technology (MEXT) between November 28 andDecember 19, 2016 by mail [9]. Respondents in the survey lived in the 14 municipalities where the 2016
Kumamoto earthquake caused severe damage. All the municipalities included in the present study met one of
the following conditions: (1) Experiencing a mainshock with a seismic intensity of 6+; (2) At least 10% of allhouses had totally collapsed (500+ buildings in the districts of Kumamoto City, an ordinance-designated city);(3) At least 20% of houses had partly collapsed; or (4) At least 15% of residents were evacuated.
The municipalities that met these conditions were Higashi-ku and Minami-ku of Kumamoto City, Koshi
City, Kikuchi City, Kikuchi-gun (Kikuyo Town and Otsu Town), Kami-Mashiki-gun (Mashiki Town, Kashima
Town, Mifune town, and Kosa Town), Uto City, Uki City, Aso City, and Aso-gun (Minami-Aso Town andNishihara Village).

2.2. Respondents
Male and female adults over 18 were systematically sampled from the poll book or the Basic Resident
Registers Network. The original sample number was 7,000, but the number of valid responses was limited to2© The 17th World Conference on Earthquake Engineering- 7f-0004 -7f-0004

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

3,772 (a valid response rate of 46.7%). Male and female valid respondents accounted for 45% and 55%,
respectively. The average respondent age was 53.24 (SD = 16.20).

2.3. Measurements
In addition to demographic variables (age and gender), earthquake risk perception, pre-earthquake
awareness of local faults, and housing damage were also measured in the survey.
2.3.1. Earthquake risk perception
The following three dimensions were included as part of a factor analysis: (1) Severity (α = .91), e.g.,serious damage will occur if an earthquake hits this region again and damage will occur in the entire region if
an earthquake hits this region again; (2) Knowledge (α = .56), e.g., the scientific understanding of earthquakes
is advancing, damage can be minimized if an earthquake hits this region again, and the damage that will becaused by an earthquake is well-known; (3) Uncertainty (α = .64), e.g., an earthquake can occur at any time,an earthquake causes various forms of damage, and the effects of an earthquake can be seen over a long periodof time. Items were rated on a five-point Likert scale ranging from 1 (completely disagree) to 5 (completely
agree).
2.3.2 Pre-earthquake awareness of local faults
Respondents were asked whether they were aware of the active faults present in their residential area
before the earthquakes occurred. Respondents’ answers were coded as either “not aware” or “aware.”2.3.3. Housing damage
Respondents were asked whether their house was completely destroyed, half-destroyed, partiallydestroyed, or had no damage.

3. Result
The score of three dimensions of risk perception (i.e., severity, knowledge, and uncertainty) was shownin Fig. 1. The residents perceived a middle level of knowledge, and they perceived a high level of severity anduncertainty. The study examined the factors influencing the three dimensions of risk perception.
A Bayesian generalized linear model (GLM) was conducted to predict the perception of severity, withgender, age, pre-earthquake awareness of local faults, level of housing damage, as well as interactive termswith pre-earthquake awareness of local faults. The quantitative variables were mean-centered, and theFig. 1 A violin plot of risk perception scores (severity, knowledge, and uncertainty)
Note: The shape indicates the distribution of data, and the black circular point indicates the average.

3© The 17th World Conference on Earthquake Engineering- 7f-0004 -7f-0004

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

Table 1 –Results of the Bayesian GLM of risk perceptions (severity, knowledge, uncertainty)
mean

se_meansd

Intercept

4.601

.000

.036

Gender(female)

.055

.000

Age

.000

.000

Awareness of local active faults(notaware)-.018

Housing damage(partially destroyed)

Severity
95%CI

n_eff

Rhat

mean

se_meansd

4.530 ~ 4.672

11169

1.000

3.065

.000

.048

.037

-.019 ~ .127

15001

1.000

-.123

.000

.001

-.003 ~ .002

26810

1.000

.003

.000

.000

.043

-.102 ~ .064

10800

1.000

-.229

.075

.000

.042

-.009 ~ .157

12376

1.000

Housing damage(half-destroyed)

.198

.000

.056

.087 ~ .308

13079

Housing damage(completely destroyed)

.185

.001

.080

.029 ~ .339

Awareness of local active faults ×
Gender(female)

-.020

.000

.045

Awareness of local active faults ×Age

-.002

.000

.050

Knowledge
95%CI

Uncertainty
95%CI

n_eff

Rhat

mean

se_mean

sd

n_eff

Rhat

2.972 ~ 3.160

12036

1.000

4.759

.000

.030

4.701 ~ 4.817

9800

1.000

.050

-.222 ~ -.025

16536

1.000

.046

.000

.031

-.015 ~ .107

12964

1.000

.002

.000 ~ .006

23803

1.000

-.002

.000

.001

-.004 ~ .000

28810

1.000

.001

.057

-.340 ~ -.119

11840

1.000

-.061

.000

.035

-.130 ~ .009

9708

1.000

-.010

.000

.056

-.119 ~ .101

13513

1.000

-.042

.000

.035

-.109 ~ .027

11374

1.000

1.000

-.099

.001

.074

-.244 ~ .048

14185

1.000

-.005

.000

.047

-.096 ~ .087

11758

1.000

14795

1.000

.197

.001

.107

-.013 ~ .406

16185

1.000

.058

.001

.067

-.075 ~ .192

13832

1.000

-.107 ~ .069

14842

1.000

.211

.000

.060

.093 ~ .329

16416

1.000

-.007

.000

.037

-.080 ~ .065

12502

1.000

.001

-.005 ~ .001

27114

1.000

-.001

.000

.002

-.004 ~ .003

24260

1.000

.000

.000

.001

-.003 ~ .002

28578

1.000

.000

.051

-.049 ~ .150

11994

1.000

.029

.001

.067

-.102 ~ .160

12697

1.000

.044

.000

.041

-.038 ~ .125

11057

1.000

.031

.001

.068

-.104 ~ .164

12723

1.000

.170

.001

.091

-.007 ~ .347

13859

1.000

.045

.001

.056

-.066 ~ .153

11670

1.000

.058

.001

.105

-.146 ~ .260

15553

1.000

-.090

.001

.141

-.368 ~ .190

15773

1.000

-.084

.001

.088

-.256 ~ .089

13754

1.000

sigma

.568

.000

.007

.553 ~ .582

27776

1.000

.746

.000

.010

.727 ~ .766

31220

1.000

.465

.000

.006

.453 ~ .477

24930

1.000

lp__

-2596.656

.028

2.551

-2602.563 ~ -2592.709

8400

1.000

-3373.385

.028

2.579

-3379.396 ~ -3369.358

8364

1.000

-1990.260

.028

2.575

-1996.178 ~ -1986.214

8599

1.000

Awareness of local active faults ×
Housing damage(partially destroyed)
Awareness of local active faults ×
Housing damage(half-destroyed)
Awareness of local active faults ×
Housing damage(completely destroyed)

Note: The interval estimation of coefficients is significant as long as 0 is not included among 95% CI.
qualitative variables were dummy coded. The analysis was performed in R using the brms package [10]. All
iterations were set to 10,000, and burn-in samples were set to 5,000, with the number of chains set to four. The
value of Rhat for all parameters equaled 1.0, indicating convergence across the four chains. Table 1
summarizes these results. The residents reporting that their house was half-destroyed (b = .20, 95% confidence
interval [CI] = .09 ～ .31) or completely destroyed (b = .19, 95% CI = .03 ～ .34) perceived severity higher
than residents whose house was either partially destroyed or not damaged (Fig. 2).
A similar Bayesian GLM was conducted to predict the perception of knowledge (Table 1). Male
residents were found to have a higher perception of knowledge compared with female residents (b = −.12, 95%
CI = −.22 ～ −.03: Fig 3_a). Furthermore, residents with pre-earthquake awareness of local faults were foundto have a higher perception of knowledge as compared with residents without pre-earthquake awareness of
local faults (b = −.23, 95% CI = −.34 ～ −.12: Fig 3_b). Older residents were also found to have a higher
perception of knowledge (b = .003, 95% CI = .000 ～ .01: Fig 3_c). An interaction effect was also foundbetween gender × pre-earthquake awareness of local faults (b = .21, 95% CI = .09 ～ .25: Fig 3_d), where

Fig 2 – The plot of the posterior distribution of parameters according to housing damage(severity).

4© The 17th World Conference on Earthquake Engineering- 7f-0004 -7f-0004

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

male residents aware of local faults were found to have a higher perception of knowledge compared withfemale residents, whereas the inverse finding was true for male and female residents without awareness of
local faults.
A similar Bayesian GLM was conducted to predict the perception of uncertainty (Table 1), but no effects
were found.

4. Conclusion
The severity of risk perception was found to differ in the present study according to the housing damage
experienced by residents. The two-thinking systems suggests that negative feeling affects risk perception
according to the experiential decision-making of System 1 [5], which is a given, considering they had a horrible
experience because of the two consecutive devastating earthquakes in the 2016 Kumamoto earthquake.
Respondents whose homes were either half-destroyed or completely destroyed were found to perceive severity
more strongly. The perception of severity can be updated by direct experience of earthquakes. This finding
supports those of previous studies indicating that people’s negative experience of natural hazards influenced
their risk perception [6]. The level of physical damage can be an important factor that affects severity.

Fig.3 – Plot of the posterior distribution of parameters of housing damage (knowledge).

5© The 17th World Conference on Earthquake Engineering- 7f-0004 -7f-0004

The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

Concerning the knowledge aspect of risk perception, the findings indicate that the older the residents,
the higher their level of perceived knowledge. This finding could be due to the fact that older residents haverelatively more direct experience of natural hazards, including earthquakes. In addition to the main effect ofpre-earthquake awareness of local faults on the perception of knowledge, the effect was also found to differ
by gender. When residents were not aware of local faults, female residents were found to have a higher levelof perceived knowledge. Awareness of hazards was also found to affect risk perception according to theanalytic decision-making of System 2 [5]. The main effect of pre-earthquake awareness was considered to bea process of System 2. Previous studies indicated that risk perception differed by gender [8]. For example, thatwomen were more concerned with safety and had a higher risk perception than men in situations where
awareness and literacy were not made available. When people lack awareness of natural hazards, System 1 ofrisk perception is based on intuitive processing, and psychological tendencies based on gender are more likely
to impact people’s knowledge of risk perception.
As for the uncertainty aspect of risk perception, no differences were found according to gender, age,
housing damage, and pre-earthquake awareness of local faults. However, residents were found to have a highlevel of uncertainty in regards to earthquakes. It is possible that, regardless of personal situations, theperception of uncertainty among most residents was likely increased by the 2016 Kumamoto earthquake. Most
residents who experienced the two consecutive large earthquakes, had not anticipated the larger mainshock to
occur two days after the large foreshock [2]. This could have been influenced by the belief that one cannot
experience another catastrophic event so soon after the last event [7]. In this context, the 2016 Kumamoto
earthquake was a natural disaster that challenged people's anticipation of risk. Thus, the experience of theearthquake affected residents’ perception of uncertainty, regardless of personal situations.
The study included a discussion on the importance of risk communication of earthquakes based onhuman cognitive mechanisms. The limitation of the current study is that it did not compare the risk perceptionof residents before and after the 2016 Kumamoto earthquake. For this reason, the effect of the earthquake on
residents’ risk perception needs to be interpreted carefully. Despite this limitation, the findings of the study
suggest that three aspects of risk perception can be influenced: (1) The perception of severity can change
according to experience of earthquakes; (2) The perception of knowledge can be influenced by prior awarenessof earthquakes; (3) The perception of uncertainty can be influenced by intuitive experiences common to mostpeople.

5. Acknowledgements
The data for this analysis was provided by MEXT [9]. This research is based on a funded research
project "Establishment of a Disaster Prevention and Management Educational Hub for Improving Disaster
Prevention Literacy among a Wide Ranging Stakeholders” (Representative: Reo Kimura, University of
Hyogo), which is supported by the SECOM Foundation for Promotion of Science and Technology.

6. References[1]

Cabinet Office. (2019): The report about the damage of the 2016 Kumamoto Earthquake. Retrieved fromhttp://www.bousai.go.jp/updates/h280414jishin/pdf/h280414jishin_55.pdf[2] Ohtomo S, Kimura R, Hirata N (2017): The Influences of Residents’ Evacuation Patterns in the 2016 Kumamoto
Earthquake on Public Risk Perceptions and Trust Toward Authorities, Journal of Disaster Research, 12 (6), 11391150.
[3] Kimura R, Ohtomo S, Hirata N (2017): A Study on the 2016 Kumamoto Earthquake: Citizen's Evaluation ofEarthquake Information and Their Evacuation and Sheltering Behaviors, Journal of Disaster Research, 12 (6), 11171138.
[4] Slovic P (1987): Perception of risk, Science, 236 (4799), 280-285.

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The 17th World Conference on Earthquake Engineering

17th World Conference on Earthquake Engineering, 17WCEE
Sendai, Japan - September 13th to 18th 2020

[5] Slovic P (2007): "If I look at the mass I will never act": Psychic numbing and genocide, Judgment and Decision
Making, 2 (2), 79-95.
[6] Wachinger G, Renn O, Begg C, Kuhlicke C (2013): The Risk Perception Paradox—Implications for Governance andCommunication of Natural Hazards, Risk Analysis, 33 (6), 1049-1065.
[7] Renn O (2017): Risk governance: coping with uncertainty in a complex world. Routledge.
[8] Slovic P (1999): Trust, emotion, sex, politics, and science: Surveying the risk-assessment battlefield, Risk Analysis,
19 (4), 689-701.
[9] Mext(Ministry of Education C, Sports, Science and Technologyof Japan). (2017): Survey study about the effect of
information of aftershock and impact on evacuation activities in the 2016 Kumamoto Earthquake. Retrieved from[10] Bürkner P-C (2017): brms: An R Package for Bayesian Multilevel Models Using Stan, 2017, 80 (1), 28.

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