This special issue focuses on “Build Back Better,” which is the key concept of the Sendai Framework for Disaster Risk Reduction (2015–2030). The Sendai Framework for Disaster Risk Reduction provides United Nations member states and economies concrete actions to protect their economic development achievements from disaster risk. However, how “Build Back Better” can be measured and linked to disaster risk reduction remain unclear.

Three papers here analyze the results of the “Life Recovery Survey Five Years After the 2011 Great East Japan Earthquake,” which was conducted in June of 2016. The first Life Recovery Survey was conducted four years after the 1995 Great Hanshin-Awaji Earthquake to document the extent to which the disaster victims had been able to rebuild their lives. Subsequently, the survey was conducted every two years until ten years after the earthquake. The survey was also conducted in the areas affected by the 2004 Niigata Chuetsu Earthquake and the 2007 Niigata Chuetsu-Oki Earthquake. Five years after the Great East Japan Earthquake of 2011, the present authors conducted a survey to document the actual situation of the disaster victims in Iwate, Miyagi, and Fukushima prefectures, which were the hardest hit by the disaster.

In addition, we analyzed the history of Nankai Trough earthquakes with the goal of preparing for the next Nankai Trough earthquake, which is predicted to occur in the near future. These results make it possible to identify issues and make recommendations on the kinds of systems that should be implemented.

It is our hope that this special issue will provide basic data to elucidate these issues.

If the Nankai Megathrust Earthquake should occur, it is clear that the disaster would become a national catastrophe. To avoid the decline of Japan caused by such earthquake first of all the proactive measures, improvement of prevention, and the reactive ones, strengthening of recovery, have to be taken by means of Disaster Resilience. Looking back on the history of Japan, we can easily understand that Japan is a lucky country, because it has never experienced the disturbances of war or huge disaster leading to a collapse of the country. However, it has become obvious that if the Nankai Megathrust Earthquake should occur, it would trigger the decline of Japan. Therefore, the Ministry of Disaster Management should be established to prevent a disaster as national catastrophe and collapse of the country. For this reason the main objectives and responses of the Ministry of Disaster Management are clarified in this paper. Especially in the phases of initial response and life rebuilding making use of the experiences of the 2016 Kumamoto Earthquake and recognizing that the Tokai Earthquake cannot be predicted, the issuance of the emergency information of the Nankai Megathrust Earthquake and its problems are discussed and summarized.

In this study, the results of a large-scale random sampled questionnaire survey of the disaster victims of the 2011 Great East Japan Earthquake are summarized. This survey was conducted during the period between March and June 2016, five years after the earthquake disaster, and included all men and women of age 20 and older who resided in the three disaster-stricken prefectures that suffered significant damage. In this study, the situation at the time of the disaster and the effective measures for disaster management in the future are examined through two questions: “Who does the disaster victims rely on for life recovery?” and “Based on this experience, who should responsibly implement the measures for disaster management in the future?” The results of these large-scale random sampled questionnaire surveys for the disasters in the past are referenced to compare the 1995 Great Hanshin Awaji (Kobe) Earthquake, the 2004 Mid-Niigata Earthquake, and the 2007 Chuetsu-Oki Earthquake. Analysis of the question, “Which persons and organizations (supporters) were relied upon in life recovery?” shows that three persons and organizations, including, a partner, children, and the town or city administration, are relied upon in all the aspects of personal or emotional, material or financial, and vital information. From all generations and kinds of supporters, people sixty and over constitute the demographic from which the least support is expected. For this generation. the family of a partner, children, mutual assistance from community associations and governmental assistance from the town/city administration are considered as the common support in all aspects. Then, comparing this with other earthquake disasters showed that a quick and careful response to all the earthquake victims by the administrative organizations is limited in large cities where relations between organizations and locals cannot be evaluated and expected. In the analysis of the question, “Who should implement the measures for disaster management in a responsible way?” it is made clear that the division of roles among self-help, mutual assistance, and governmental assistance can be summarized in the following four patterns: Mainly by governmental assistance, mainly by self-help, in cooperation with mutual assistance and governmental assistance, and in cooperation with of self-help, mutual assistance, and governmental assistance, altogether. Comparisons between all the earthquake disasters, lead to the understanding that the disaster victims who experienced a large-scale disaster consider that the measures for disaster management should be implemented by through self-help, mutual assistance, and governmental assistance, altogether, regardless of the disaster and local characteristics. In Japanese society it seems that the division of roles among self-help, mutual assistance, and governmental assistance could generally be proposed.

The purpose of this study is to compare the effect size of seven critical elements on the life recovery in three prefectures, Iwate Prefecture, Miyagi Prefecture, and Fukushima Prefecture, which were severely damaged by the Great East Japan Earthquake Disaster. This study used the 2016 Tohoku Life Recovery Survey (N = 2111, response rate: 35.2%) for the analysis. The dataset was divided into each prefecture sample to compare the effects of seven critical elements on life recovery in the three prefectures. We obtained samples from Fukushima (N = 603), Iwate (N = 781), and Miyagi (N = 727). First, the distribution of life recovery by the three prefectures was confirmed. The results showed that those affected by the Great East Japan Earthquake disaster in Miyagi have a higher quality of life recovery. Finally, we compared the effects of seven critical elements on life recovery among the three prefectures’ models using GLM analysis. From the comparison of effect size (partial η²) and discussion, three points are shown. 1) In the Fukushima model, the effect size of physical/mental stress management and social ties was larger than in the other models. 2) The effects of 1) were caused by the experience of diaspora (nuclear disaster-caused displacement). 3) If forced diaspora can create good relationships with local people, the positive effects of social ties on life recovery for such people are larger than for those who have not experienced diaspora.

This study aims to clarify: 1) the life recovery trajectories that the Great East Japan Earthquake (GEJE) survivors have followed; 2) the interrelationships between the life recovery trajectories and pre-existing inequalities as well as post-event social environmental changes; and 3) pre- and post-GEJE characteristics of the survivors with stagnant life recovery. The analyses are based on five-wave panel data from “Natori City Life Recovery Population Panel Survey” (n = 316), which was conducted in Natori City, Miyagi Prefecture from the fourth to the tenth years after the GEJE. Cluster analysis was performed to classify the life recovery trajectories and identified six distinct patterns. Two types of them remained at a low level of life recovery throughout the five-wave survey. Multiple correspondence analysis was conducted to analyze the relationships among life recovery trajectory patterns, pre-existing inequalities, and post-event social environmental changes. As a result, the survivors in these two types were typically older people, small household members, poor people, and persons with disabilities. These findings indicate that people with vulnerabilities who would experienced daily life troubles before the GEJE were also struggling even after the disaster.

The main goal of the conceptual framework of this mini special issue, which is based on the International Symposium on Human Survivability 2016 (ISHS2016), is to provide a fresh look at the global challenges facing humanity in the areas of energy, water, food, population, disease, etc. The ISHS2016 focused on enhancing resilience to extreme or large-scale disasters that may threaten the well-being of present and future generations. By considering past, present, and future dimensions, we aimed to develop a holistic approach that integrated various research fields.

The symposium brought together scholars from not only the natural and social sciences but also the humanities. The idea behind this was that we need to go beyond the “silo-based” approach, where handling disasters is something left to experts with specialized knowledge. The integration of the knowledge of scholars from different academic fields and backgrounds could provide novel solutions to the problem of how to enhance our resilience to future disasters.

This mini special issue aims to identify key issues in prioritizing several different types of disasters in terms of their time frames and impact frames, with the knowledge that the disasters are of completely different types and that the capacity of each institution and the consciousness of society in terms of each issue are all unequal. From those, we may identify the main characteristics of “low probability and high impact disasters,” as well as the different approaches that are needed. Disasters vary from infectious diseases to space weather, tsunamis, and earthquakes.

Insurance risks have traditionally been borne in reinsurance markets. However, in the 1990s, after a series of huge natural disasters, and consequently massive insurance payments, the reinsurance markets reduced their capacity to bear risks. Insurance-linked securities, such as CAT (catastrophe) index futures contracts, were created to provide insurers with a way to transfer insurance risks to capital markets. However, two obstacles are preventing CAT index futures from being traded: the basis risk between insurers’ risks and the futures payoff, and adverse selection between informed insurers and uninformed investors in capital markets. This study investigates the conditions under which CAT index futures, whose payoff is the average of insurers’ losses, can be traded, and insurers choose CAT index futures rather than reinsurance to transfer their risks. The results show a trade-off: CAT index futures can be traded if the number of insurers in the index is large enough, since averaging multiple insurers’ losses can mitigate adverse selection in the index futures’ payoff. However, if the number of insurers in the index is too large, insurers prefer reinsurance to index futures due to the high basis risk in the futures’ payoff.

Space weather, or the disturbances of the plasma environment driven by the magnetic activities in the Sun in geospace, has become a potential source of disaster for modern society, which is increasingly dependent on its space infrastructure and large-scale power grids. Recently, independent pieces of evidence have been found that support the possibility of extremely intense space weather driven by a “superflare,” a solar phenomenon that modern society has never experienced. This paper reviews state-of-art studies of superflares and their potential impacts.

Debris flow is an important natural hazard in mountain zone because it can threaten human lives with very little warning. Since laboratory experiments on debris flows at real scale are difficult to perform, numerical simulations are important in evaluating the impact of such flows. Among several candidate models, the smoothed particle hydrodynamics (SPH) is a particular attractive numerical method for this purpose. SPH is a particle-based numerical hydrodynamic method originally developed in the astrophysical field before extension to elastic bodies. Several works have already tested the applicability of SPH to debris flow, despite there are only few detailed validations. In this report, thus, we aimed to check the applicability of SPH to debris flows. Since the accurate treatment of the elastic bodies tends to be computationally expensive, we have developed a massively parallel SPH code. A comparison between laboratory experiments and numerical simulations using SPH showed qualitatively similar features, though there are differences in quantitive comparisons.

In the history of terrestrial lifeforms, several different kinds of natural disasters can be classified in biological history since the Phanerozoic period. The most serious disasters can be classified as (1) volcanic disasters, (2) asteroid impacts, and (3) climate disasters, in reference to the root cause of low-probability, high-consequence (LPHC) events. However, on a shorter timescale, mankind is more vulnerable to frequent disasters, such as (i) large floods, (ii) epidemics, (iii) earthquakes, (iv) tsunamis, and (v) small-medium scale volcanic eruptions. These are known as high-probability, low-medium-consequence events (HPLC). LPHC occurrences have a very low probability of occurring, but they would have catastrophic consequences. HPLCs occur more frequently, with most of them having decadal frequency. They cause local fatalities, but they are never global in scale. In this study, these events are classified and evaluated based on the potential risk for human civilization. We also discuss how to incorporate different considerations related to prioritizing different disasters, focusing on whether insurance mechanisms can be applied or not.

We performed stereomicroscopic, X-ray diffraction (XRD), and water-soluble components analyses on volcanic ash discharged from the June 17, 1962 eruption of Yakedake volcano. Ash samples were collected without surface soil and rainfall contamination. Pyrite and gypsum were identified, as well as other previously reported constituent minerals, and 1,250 mg/kg of Cl and 10,800 mg/kg of SO₄ as water-soluble components. The presence of hydrothermal alteration minerals and large amounts of water-soluble components indicates that the eruption was a phreatic event that originated in a hydrothermal alteration zone.

Brahmaputra River comprises the characteristics of a braided channel and suspended sediment-dominant river. Frequent changes in the river course have led to severe bank erosion. In particular, Tangail and Manikganj districts have recently become bank erosion-prone areas. To predict vulnerable locations based on bank erosion, we aimed to understand the behavior of the braided channel by conducting a numerical simulation and satellite data analysis in this study. We employed a depth-integrated 2-D numerical model for water and sediment transport, which was originally proposed by Takebayashi et al. and modified by Harada et al. by introducing a new treatment of suspended sediment. In addition, bathymetry data were created using a series of satellite data information to successfully conduct the simulation. In this study, we focused on two aspects. The first point is the skewing of flow discharge along multiple channels, which belongs to the area of interest, as a large-scale phenomenon. The second point is changing the local geometry of the sand bar and changing the flow pattern, as a small-scale phenomenon. To consider the two different scales, we employed the computation domain as an entire channel. Our results indicate that the numerical model is successfully verified using satellite data information, and the two-scale phenomena are successfully described. Regarding the large-scale phenomenon, our results indicate that the distribution of higher flow rates activates various geomorphological changes, including riverbed evolution, channel changes, and bank erosion. On the other hand, small-scale phenomena, such as the rapid appearance of sand bars and changes in the water course, are directly related to bank erosion.