6. A Study on the Utilization of the Tsunami Hazard Evaluation in Japan
6.5 Proposal type hearing for policy formulation on the utilization of the tsunami hazard evaluation
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6.5 Proposal type hearing for policy formulation on the utilization of the tsunami hazard
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1) Comment from the tsunami hazard evaluation object persons #1:
This information will provide a basis for developing an overall policy on disaster prevention measures.
If simple results can be provided, then it will be easy to set up mitigation measures.
This information can be utilized for assessing the level of evacuation. However, this assessment may prove difficult in practice.
This information can be used as a basis for making policy decisions and providing the public with explanations.
This information can be utilized as the tsunami hazard evaluation analysis.
This information is only necessary that the probability will become advantageous to subsidies subject and disaster mitigation plans. For example, even if this information to resolve a bottleneck against evacuation, it will not be easy way. In such a case, it is expected to be utilized as a basis for disaster mitigation plans. Thus, respondents requested the development of a mechanism for promoting business using these simulation results.
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Fig. 6-12 shows how the mitigation assessment can be utilized to prioritize municipalities’
disaster mitigation measures.
Fig. 6-12Utilization of the mitigation assessment by municipalities to prioritize disaster mitigation measures and to assess municipalities’ utilization of priority measures for implementing disaster mitigation measures during a specific year and their business volumes.
30 15 5
10 1
0 5 10 15
Ａ市 Ｂ市 Ｃ市 Ｄ市 Ｆ市
Tsunami heights occurred with a probability of 50%
within the next 30 years in A prefecture.
○○Prf.
Disaster Mitigation Plane
A city B city C city D city E city
Comme 1. Disaster commer
A City: Since maximum tsuna we will implemen
speed up "ev embankm
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2) Comment from the tsunami hazard evaluation object persons #2:
Respondents suggested that the mitigation assessment results could be used to facilitate the formulation of policies for prioritizing tsunami countermeasures.
This plan will serve as the basis for developing an overall policy on disaster resilience measures.
This plan can be utilized as supplementary explanatory material and can be incorporated within city planning as well.
A long-term goal for town development is required. However, developing long-term disaster prevention plan, compared with medium-term and short-term plans, is difficult.
If there is probability theory, not only disaster mitigation plans but also comprehensive plans and so on, must be addressed will be encouraged, it will be a measure of the roadmap for tsunami countermeasures.
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Fig. 6-13 shows the tsunami hazard assessment, which is setting of the tsunami level to be considered that conforms to the occurrence probability.
Fig. 6-13 Tsunami hazard assessment in relation to the study of facilities.
3) Comment from the tsunami hazard evaluation object persons #3:
This assessment provides a reference for thinking about practical countermeasures and will also serve as a basis for requesting funds to construct coastal levees for prefectures.
Within various countries as well as in Japanese prefectures, a growing trend of utilizing gradual tsunami hazard assessment results when considering disaster prevention measures is apparent.
These results can be used within municipalities as well.
A limited budget was available to the institution that developed the L1 category tsunami (L1), which is high occurrence probability tsunami, and L2 category tsunami (L2), which is maximum level tsunami in Ibaraki Prefecture after the Tohoku Earthquake. Ongoing efforts should be based on a thorough investigation by NIED that generates detailed data.
NIED Tsunami Hazard Assessment Coastal conservation facility Design level
Tsunami height assumed to arrive at a certain frequency (return period:
several decades to once every hundred and several decades)
Utilization for setting
"Design tsunami water level"
○Relatively frequent tsunami (L1 tsunami) is is defined by calculating the tunami height of probabilistic evaluation for the class historical earthquake occurring once in the past decades to hundreds of years, and design the tsunami height of L1 .
○ The maximum class tsunami (L2 tsunami) is defined by calculating probabilistic evaluated tsunami height for the historical earthquake which has extremely low occurrence frequency, even thought causes serious damage occurs.
Tsunami height●m
Tsunami height●m
Tsunami height●m
Tsunami height●m Coastal area
A
Coastal area B
Coastal area C
Coastal area D
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Fig. 6-14 shows examples of customized utilization of the results of the tsunami within municipalities.
Fig. 6-14 Tsunami hazard assessment that enables the development of further detailed tsunami countermeasures.
4) Feedback from the tsunami hazard evaluation object persons:
The detailed tsunami frequency data along with data on the height and arrival time of a tsunami that are presented in the hazard evaluation results are easily comprehensible.
The administration must respond to the simulation results obtained for the prefecture if differences from the simulation results in the prefecture are known.
The results could be used in delivery courses conducted by municipalities.
✔Wave source model
✔Tsunami height
✔Inundation area etc.
Validation of simulation results performed by local government using NIED provided data 5m≦H<10m
Tsunami height 1m≦H< 2m 2m≦H< 3m 3m≦H< 5m 20m≦H<30m 10m≦H<20m 30m≦H
87 7. Conclusion
The results of the survey conducted on the utilization of tsunami hazard information by municipalities are summarized below.
1) A tsunami hazard assessment is expected not only for the tsunami level of only the largest class but also for expectation that gradual evaluation can be performed. However, it is not possible to estimate tsunami for the general population against the tsunami of high occurrence probability (e.g., L1 category tsunami). Many of the respondents felt that the explanation was difficult to comprehend.
2) A majority of municipalities (70%) have published tsunami hazard maps. These maps are used for developing guidelines for raising public awareness and conducting evacuation drills for residents.
Further, they specifically describe actions to be taken by residents and evacuation procedures.
3) The survey revealed equal numbers of municipalities that have actively incorporated and utilized information on tsunami hazards and those that have not strongly pursued this approach. Active users suggested that an evaluation based on scientific evidence could be used to promote countermeasures against tsunamis of a scale that is more common by promoting or prioritizing disaster mitigation measures. However, those who were more critical felt that staff and residents found it difficult to understand the information presented. The majority of municipalities (80%) suggested that workshops and meetings should be organized to provide explanations and disseminate information.
4) A widely held view was that submerged cables are required to transmit real-time tsunami information to relevant municipalities at an earlier stage than was previously done. More than 90%
of the surveyed municipal authorities were in favor of utilizing this information for alerting the public and evacuating residents immediately after the occurrence of a disaster.
5) A total of 60% of the municipal authorities who wanted to know the arrival time of a tsunami were expected to provide residents with information using the relevant website, smart phones, and brochures as tools for disseminating the assessment results.
88 8. Adopted Recommendations
This study was conducted to assess the possibility of utilization of tsunami hazard assessments by municipalities. The study was also aimed at determining the current implementation status and issues relating to tsunami measures and compiling the views and experiences relating to evacuation, including negative ones, of municipalities.
(1) Recommendations for agencies that develop the tsunami hazard evaluation
1) Introduction of an evaluation of epistemological uncertainty relating to hazards．
· An assessment of epistemological uncertainty is also necessary for evaluating hazards.
· In general, random variation (fluctuations attributed to fundamentally unpredictable random properties) and epistemological uncertainty (resulting from incomplete knowledge and data) feature in evaluations of uncertainty. Theoretical uncertainty has not been sufficiently addressed, even in areas such as ground motion prediction maps. An assessment of epistemological uncertainty is important in the evaluation of tsunami hazards that entail a high degree of uncertainty.
· Hazard assessments that entail an evaluation of uncertainty should not be conceptualized in restricted scientific terms but should also incorporate engineering concepts.
· If the earthquake headquarters performs the hazard assessment, not only a physical evaluation but also an engineering-based evaluation of uncertainty should be emphasized.
· A lesson derived from the experience of the Tohoku Region Pacific Offshore Earthquake is that efforts to evaluate hazards conducted at headquarters should focus on evaluating epistemological uncertainty from the front.
· Logic trees can be used as an analytical tool for evaluating epistemological uncertainty. However, it is also necessary to develop a methodology for constructing a logic tree that can appropriately express uncertainty.
2) Clarification of preconditions and the process of developing a tsunami hazard assessment.
· It is necessary to clarify prerequisites and the process of developing a tsunami hazard assessment
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to enable the evaluation of risks based on the hazard assessment.
· To ensure accountability to users who conduct risk assessments based on the results of a tsunami hazard assessment, it is necessary to maintain transparency by developing the assessment methodology, including preconditions. Consequently, users will be able to create their own hazard assessments by changing the prerequisites.
· This study believe that it is important to prepare a tsunami hazard assessment based on disaster prevention and engineering perspectives. However, it is important to pay attention for a tsunami hazard assessment that is closer to the safety margin, depending on the user's position, risk, it is necessary to keep in mind that it may be difficult to use for evaluation.
·A lesson derived from the experience of the Tohoku Earthquake is that efforts to evaluate hazards should focus on the evaluation of epistemological uncertainty from the front.
· Logic trees can be used as an analytical tool to evaluate epistemological uncertainty. However, it is also necessary to develop a methodology for constructing a logic tree that can appropriately express uncertainty.
3) Establishment of a method for assessing the flooding depth hazard in the inundation area.
· Conducting a probabilistic tsunami hazard assessment of the inundation area and depth in a terrestrial environment with relates to structural damage, is more important than obtaining information on the height of coastal tsunamis.
· As damage inflicted by coastal tsunamis rather than their height is the subject of a hazard assessment, land inundation areas and flooding depth are assessed. For infrastructure design, it can be informed at the structure design site with having high utility value. However, because the tsunami inundation is influenced by structural factors, including the detailed topography and conditions of coast and land areas, it is important to structural design a probabilistic evaluation method for the uncertain problem solving.
4) Development of a released to the public system to enable the utilization of a variety of
90 tsunami hazard assessments.
Experts who conduct tsunami risk assessments would benefit from an open system that enables a variety of tsunami hazard assessments (including the prerequisites for developing an assessment) to be utilized.
Various experts can utilize the tsunami hazard evaluation, requiring different information for different purposes. Users need to develop a system that enables them to properly utilize various tsunami hazard assessments according to their purpose.
5) Periodic updating of tsunami hazard assessments.
· Maintenance announcement is critical for sustained utilization of a tsunami hazard assessment.
· A hazard assessment entails forecasting based on scientific knowledge and can change in the future as a result of the acquisition of new knowledge and data regarding the probability of earthquake occurrence, as well as updated topographical data and more advanced and sophisticated hazard evaluation methods. Thus, it is necessary to continue to incorporate new knowledge into the development of observation and analytical technologies on an ongoing basis and to appropriately adjust and refine hazard assessments.
6) Points to be covered and incorporated in the hazard assessment to avoid misplaced confidence on the part of those designing the assessment.
·The absence of inundation across the range shown in the hazard map, the designers of the hazard assessment should clarify the purpose and limits of the hazard assessment to avoid misplaced confidence on the part of users of the assessment. Specifically, they should specify the scope of application and points of caution at the time of application as conditions relating to the provision of information.
· One of the lessons learned from the Great East Japan Earthquake relates to the issue of misplaced confidence. Authorities were confident that flooding would not occur above the range indicated in the hazard map. The developers of the hazard assessment should be aware of the danger of
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misplaced confidence among users associated with the transmitted information. They should clearly state the purpose and scope of application of the assessment and should outline the method of setting preconditions such as how to handle structural conditions.
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(2) Recommendations for users of the tsunami hazard evaluation
1) Proper understanding and use of the tsunami hazard evaluation can be fostered through the promotion of consultations between the developers of the assessment and users who conduct risk assessments that entail highly specialized information needs.
Because a tsunami hazard assessment entails highly specialized information, members of the public, municipalities, and the personnel of disaster resilience companies may find it difficult to directly apply this information. Experts who conduct risk assessments, and are therefore direct users of the tsunami hazard evaluation, should collaborate with the developers of the tsunami hazard evaluation. Consequently, the assessment can be tailored, stepwise, to achieve the intended purpose, thereby encouraging its wider application.
Municipality representatives and residents who want to know about effective countermeasures to mitigate the impacts of maximum class tsunami should be provided with appropriate information.
Users should be provided with concrete examples of the assessment’s application to further their understanding. Specifically, these examples should be incorporated into guidelines on the use of the assessment by the general public, local public entities, and enterprises. In addition, educational materials and supplementary course readings on tsunami hazard assessments should be developed for schools to raise the awareness of students.
2) Risk assessments based on the tsunami hazard evaluation and their utilization within regional disaster mitigation efforts.
Public dissemination of the tsunami hazard evaluation will enable the development of regional measures based on risk assessments relating to different kinds of tsunamis. Plans and countermeasures based on information on a wide range of tsunami heights, arrival times, inundation ranges, immersion depths, flow velocity and direction, duration, time-series, and water level fluctuations are also anticipated.
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Through the conduct of a risk assessment based on an evaluation of tsunami hazards, information relating to risks can be incorporated into assessments of land use, structural planning, and investments. Establishing tsunami categories that are commensurate with local tsunami measures
It is necessary to establish tsunami categories in consultation with stakeholders in target areas that are susceptible to tsunamis. In addition, the planning of tsunami-resistant facilities to help mitigate disasters as well as non structural measures relating to land use and evacuation are necessary.
In the United States, probabilistic assessments have included a consideration of the probability of earthquake occurrence. In Japan, Level 1 and Level 2 categories have been established based on a probabilistic conception. However, a discussion is still insufficiently to contrast with hazard assessment. In addition, because residual risk exists regardless of what kind of occurrence probability setting is established, the development of non structural measures is imperative.
94 References
[1] Fujiwara, H., Nakamura, N., Morikawa, S., Aoi, S. and Kawai1, S. et al., (2013), Tsunami hazard assessment project in Japan, JpGU, HDS28-04.
[2] Hirata, K., Fujiwara, H., Nakamura, H., Osada, M. and Ohsumi, T. et al. (2014), Tsunami hazard assessment project in Japan, JpGU, HDS28-04.
[3] Hirata, K., Fujiwara, H., Nakamura, H., Osada, M. and Ohsumi, T. et al. (2017), Probabilistic tsunami hazard assessment based on the long-term evaluation of subduction-zone earthquakes along the Sagami Trough, Japan, AGU.
[4] TOYAMA, N., Hirata, K., Fujiwara, H., Nakamura, H. and Morikawa, N. (2014), A set of characterized earthquake fault models for the probabilistic tsunami hazard assessment in Japan, JpGU, HDS28-03.
[5] Korenaga M., Hirata, K., Fujiwara, H., Nakamura, H. and Morikawa, N. et al. (2014), Large slip area in characterized Tsunami source model toward Tsunami Hazard assessment, JpGU, HDS27-17.
[6] Akiyama N., Hirata, K., Fujiwara, H., Nakamura, H. and Morikawa, N. et al. (2014), A new calculation method for seabed displacement due to fault slip by boundary integration, JpGU, HDS27-14.
[7] Abe, Y ., Hirata, K., Fujiwara, H., Nakamura, H. and Morikawa, N. et al. (2014), Uncertainty for sunami hazard caused by heterogeneous slip on the characterized source model, JpGU, HDS27-16.
[8] Saito, R., Hirata, K., Fujiwara, H., Nakamura, H. and Morikawa, N. et al. (2014), Inundation hazard mapping toward probabilistic tsunami hazard assessment, JpGU, HDS27-15.
[9] Osda, M. Nakamura, H., Hirata, K., Ohsumi, T. and Fujiwara, H. et al. (2014), An overview on current status of public disclosure for tsunami hazard information in and around Japan, JpGU, HSC25-P10.
[10] Ohsumi, T., Nakamura, H. Hirata, K., Osda, M. and Fujiwara, H. et al. (2014), Tsunami hazard inventory survey of utilize for municipalities, JpGU, HSC25-P08.
[11] Meteorological Agency’s leaflet "Tsunami warning changed"
http://www.jma.go.jp/jma/kishou/books/tsunamikeihou/
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