著者

Hideaki Goto Yasuhiro Kumahara Shoichiro Uchiyama Yoshiya Iwasa Tomoru Yamanaka Rinako Motoyoshi Shun Takeuchi Sho Murata Takashi Nakata

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.14, no.6, pp.894-902, 2019-09-01 (Released:2019-09-01)

参考文献数

12

被引用文献数

7

---

Record-breaking heavy rainfall in July 2018 caused an extremely large number of slope movements over a broad area of western Japan. We mapped the distribution of slope movements in the southern part of Hiroshima Prefecture through an interpretation of aerial photographs that were acquired after the rainfall by the Geospatial Information Authority of Japan, and counted a total of 8,497 slope-movement starting points. The widespread distribution of slope movements – from Etajima City of Hiroshima Prefecture to Kasaoka City of Okayama Prefecture – suggests that the heavy rain affected a very large area. The starting points of debris flow during this disaster were commonly close to the crest of mountain ranges. We compared the distribution of slope movements to the 24-hr rainfall accumulation during the heaviest rainfall event to clarify the factors that caused regional difference in slope-movement distribution. We found the area of highest density of the slope movements was consistent with the area receiving a cumulative rainfall of >250 mm. This observation indicated that the position of slope-movement starting points was not related to differences in geology.

著者

Hiroaki Isobe Takuya Takahashi Daikichi Seki Yosuke Yamashiki

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.17, no.2, pp.230-236, 2022-02-01 (Released:2022-02-01)

参考文献数

55

被引用文献数

1

---

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.

著者

Shigeki Senna Atsushi Wakai Haruhiko Suzuki Atsushi Yatagai Hisanori Matsuyama Hiroyuki Fujiwara

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.13, no.5, pp.917-927, 2018-10-01 (Released:2018-10-01)

参考文献数

22

被引用文献数

13

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During the 2016 Kumamoto earthquakes, two earthquakes of seismic intensity 7 were observed in Mashiki Town, the foreshock (MJMA 6.5) of April 14 and the main shock (MJMA 7.3) of April 16, resulting in significant damage to structures near the fault. The distribution of damage of houses and other buildings [1] showed a tendency in which damage was concentrated in areas near the surface earthquake fault where the main shock presumably occurred. However, there were locations with slight damage even though they were immediately above the fault and locations with a relatively significant damage even though they were far from the fault. These phenomena are highly likely to be a result of soil structure. First, we built an initial geologic model by collecting boring data in areas of the Kumamoto plain near the fault where damage was severe. Next, we observed microtremors, collected earthquake observational records, and adjusted the layer thickness and S-wave velocity of the initial geologic model. Finally, we built a shallow and deep integrated ground model, compared it to the building damage distribution, and discussed the implications.

著者

Yoshiaki Kawata

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.17, no.2, pp.164-182, 2022-02-01 (Released:2022-02-01)

参考文献数

11

被引用文献数

1

---

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.

著者

Kana Moriyama Daisuke Sasaki Yuichi Ono

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.13, no.6, pp.1007-1014, 2018-11-01 (Released:2018-11-01)

参考文献数

26

被引用文献数

22

---

After the Sendai Framework for Disaster Risk Reduction is adopted, a global database as a tool to monitor disaster loss and damage databases is required. Several disaster loss and damage databases are in use globally. This paper aims to explore how the existing databases vary in three aspects of threshold, spatial resolution, and data quality control, as well as the limitations of the existing databases. We review previous studies comparing the existing global databases and extract the differences and limitations. The threshold of EM-DAT is clear, but its threshold results in ignoring small-scale disasters that DesInventar captures. The differences in disaster threshold create different pictures of disaster losses and/or risks. Regarding spatial resolution, only DesInventar provides disaster impact data at a municipal level, while others provide information at a country level. The limitations of the existing global database are categorized into four aspects, as follows: lack of disaggregated data, limited spatial coverage and resolution, insufficiency of completeness and reliability of data, and insufficient information on indirect loss. The implication from our findings is that, in order to complement the limitations of the existing disaster loss databases to use for decision making on disaster risk reduction, the following are required: cross-checking of data across different databases; complementary disaster loss data; and collection of an exhaustive and firsthand dataset with a transparent and internationally consistent methodology by policy makers.

著者

Amaly Fong Lee Adan Vega Saenz

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.17, no.7, pp.1192-1198, 2022-12-01 (Released:2022-12-01)

参考文献数

28

被引用文献数

1

---

The work performed by the urban search and rescue (USAR) teams is, from every standpoint, difficult to exactly define, since their main mission, which is to save lives, is joined by a series of tasks typical of disaster risk management, which makes them one of the most complex professions and therefore, with the strictest training requirements. Within these requirements, the fact is that USAR teams must be trained to serve a wide population diversity, which also involves the skills to manage critical situations where an inclusive approach is vital. To face this challenge, it is necessary to develop inclusive strategies according to the reality of these teams. In this article, the authors perform a deep analysis to the existing literature and by means of an exhaustive evaluation get to propose an inclusive model for the USAR teams. This model allows to define not only the reach of the inclusion term in these teams, but also helps to establish strategies to reformulate the training plans and programs of recruiting and retention of new members.

著者

Tetsuya Nakamura Steven Lloyd Atsushi Maruyama Satoru Masuda

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.16, no.5, pp.840-865, 2021-08-01 (Released:2021-08-01)

参考文献数

59

被引用文献数

1

---

This paper statistically analyzes residents’ understanding of problems related to radioactively contaminated water discharged from nuclear power and nuclear reprocessing plants. Moreover, this paper examines their impact on the surrounding fisheries by using the cases of La Hague, Sellafield, and Fukushima Daiichi Nuclear Power Plant. Survey data shows that more than 60% respondents disagree with the release of contaminated water, and this sentiment is particularly strong among both British and French respondents. Regarding seafood caught in the vicinity of the nuclear power and nuclear reprocessing plants, although British respondents noted that they hold it in high regard, many people do not purchase this seafood. In contrast, many Japanese respondents reported that they were less concerned, and thus, willingly purchase seafood caught off the coast of Fukushima Prefecture. In all three countries, many people did not trust government information on the release of contaminated water. Compensation to the affected people was provided by the central government, companies involved, and local governments, in that order. Japanese and British respondents reported higher expectation for compensation as compared to French respondents. Japanese and French respondents noted that they have knowledge of radioactive materials and contaminated water, and many of them purchased seafood caught in the vicinity of the nuclear power and reprocessing plants. British respondents were the most opposed to the release of contaminated water, whereas Japanese respondents were the least reliant on government information about the release of contaminated water. Finally, among those who trusted information from the government and retailers, French respondents were the least concerned about contamination. French respondents were also the least likely to expect any compensation for the fishermen affected by contamination. Both British and French residents around the affected plants expected the central government to compensate the affected fishermen, whereas those who did not reside around the affected plants did not expect the fishermen to be compensated. French respondents were more likely to expect compensation from the local governments; affluent respondents were more likely to expect the compensation to be funded by taxation, whereas less affluent respondents expected them to be funded by donations. Respondents who were more skeptical of government information wanted the companies involved to compensate the fishermen. British respondents reported a tendency for wanting the companies involved to provide this compensation, and did not support the concept of compensation provided through donations.

著者

Noriko Shimasaki Hideaki Morikawa

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.16, no.1, pp.61-69, 2021-01-30 (Released:2021-01-30)

参考文献数

49

被引用文献数

4

---

A new infectious disease caused by a novel coronavirus (COVID-19) has spread rapidly worldwide in 2020. The COVID-19 pandemic in Japan can be viewed as an urban disaster because transmission of this respiratory disease tends to occur in densely populated areas. A scientific understanding of the pathogen itself, the cause of the disaster (infectious disease), as well as infection control measures, are important to implement robust and appropriate countermeasures. This review discribes the features, especially the modes of transmission, of COVID-19 and the principles by which infection control is possible using one of the most effective infection control measures – personal protective equipment (PPE). Because COVID-19 is often transmitted to others by asymptomatic individuals through droplets, even those who are unaware of their infection should wear masks to prevent the spread of droplets that may contain the virus and effectively control the spread of disease. However, given the worldwide competition for masks and the urgent requirement of effective controls, it is necessary to conduct further research to establish a system that can supply adequate numbers of masks to regions where many people are infected in the country, with no shortage of masks, in order to make the country more resilient to disasters caused by infectious diseases in the future.

著者

Ryohei Kato Ken-ichi Shimose Shingo Shimizu

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.13, no.5, pp.846-859, 2018-10-01 (Released:2018-10-01)

参考文献数

36

被引用文献数

25

---

Torrential rainfall associated with linear precipitation systems occurred in Northern Kyushu, Japan, during July 5–6, 2017, causing severe damage in Fukuoka and Oita Prefectures. According to our statistical survey using ground rain gauges, the torrential rainfall was among the heaviest in recorded history for 6- and 12-h accumulated rainfall, and was unusual because heavy rain continued locally for nine hours. The predictability of precipitation associated with linear precipitation systems for this event was investigated using a cloud-resolving numerical weather prediction model with a horizontal grid interval of 1 km. The development of multiple linear precipitation systems was predicted in experiments whose initial calculation time was from several hours to immediately before the torrential rain (9:00, 10:00, 11:00, and 12:00 Japan Standard Time on July 5), although there were some displacement errors in the predicted linear precipitation systems. However, the stationary linear precipitation systems were not properly predicted. The predictions showed that the linear precipitation systems formed one after another and moved eastwards. In the relatively accurate prediction whose initial time was 12:00 on July 5, immediately before the torrential rainfall began, the forecast accuracy was evaluated using the 6-h accumulated precipitation (P6h) from 12:00 to 18:00 on July 5, the period of the heaviest rainfall. The average of the P6h in an area 100 km×40 km around the torrential rainfall area was nearly the same for the analysis and the prediction, indicating that the total precipitation amount around the torrential rainfall area was predictable. The result of evaluating the quantitative prediction accuracy using the Fractions Skill Score (FSS) indicated that a difference in location of 25 km (50 km) or greater should be allowed for in the models to produce useful predictions (those defined as having an FSS ≥0.5) for the accumulated rainfall of P6h ≥50 mm (150 mm). The quantitative prediction accuracy examined in this study can be basic information to investigate the usage of predicted precipitation data.

著者

Jeffrey S. Perez Hiroyuki Tsutsumi Mabelline T. Cahulogan Desiderio P. Cabanlit Ma. Isabel T. Abigania Takashi Nakata

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.10, no.1, pp.74-82, 2015-02-01 (Released:2019-07-01)

参考文献数

35

被引用文献数

7

---

The 1,250-km-long, NNW-trending, arc-parallel Philippine fault, one of the world’s most active tectonic structures, traverses the Philippine archipelago and has been the source of surface-rupturing earthquakes during the last four centuries. In this paper, we will discuss Philippine fault distribution and segmentation in Mindanao Island by integrating detailed fault mapping together with new geological and paleoseismic data and the analysis of historical surface-rupturing earthquakes. Using geometric segmentation criteria, we have identified nine geometric segments separated by discontinuities such as en echelon steps, bends, changes in strike, gaps, steps and bifurcation in the surface trace. Fault segments ranges from 20 to 100 km in length and are capable of generating earthquakes of Mw6.6 to Mw7.4. The results of our study have important implications for earthquake generation potential and seismic hazard assessment of the Philippine fault in Mindanao Island.

著者

Masashi Nagai Setsuya Nakada

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.17, no.5, pp.829-838, 2022-08-01 (Released:2022-08-01)

参考文献数

30

---

A hydrovolcanic eruption in the early hours of October 8, 2016 triggered a power outage of about 29,000 houses (∼50,000 habitants) in the Aso caldera area, Kyushu, Japan. Although it was recovered naturally by the early morning of that day, the power outage occurred again in the evening following rainfall that began in the afternoon. The power supply in the caldera area had been temporarily maintained despite the heavy landslide damage due to strong earthquakes in April 2016, without the supplemental transmission lines for the normal standard. The power outage is considered to have been due to the insulator flashover in the power substation, Ichinomiya, Aso, around which the mass of volcanic ash was about 3,000 g/m2 or less (≤3 mm thick). This outage resulted from high electric conductivity of the volcanic ash that was wetted with strongly acidic water dammed in the crater before the eruption. This may be one example of the power outage incident due to thin ash fall.

著者

Hiroshi Inoue Zhengying Fan Melchor Lasala Robert Tiglao Bartolome Bautista Debbie Rivera Ishmael Narag

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.10, no.1, pp.35-42, 2015-02-01 (Released:2019-07-01)

参考文献数

10

被引用文献数

3

---

We designed a seismic intensity meter and a data collection network for use in the Philippines. The station unit deployed consists of a digital acceleration sensor with 0.1 gal noise and a compact Microsoft Windows PC. The station unit, which is designed to be installed in local government offices, calculates values every 10 seconds for the PEIS (Philippine Earthquake Intensity Scale), and these values are shown on a display and transmitted to the main PHIVOLCS office over the Internet. One hundred units to be deployed throughout the country are now being distributed to offices.

著者

Namiko Sakurai Koyuru Iwanami Shingo Shimizu Yasushi Uji Shin-ichi Suzuki Takeshi Maesaka Ken-ichi Shimose Paul R. Krehbiel William Rison Daniel Rodeheffer

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.16, no.4, pp.778-785, 2021-06-01 (Released:2021-06-01)

参考文献数

26

被引用文献数

3

---

The National Research Institute for Earth Science and Disaster Resilience deployed a lightning mapping array (LMA) in the Tokyo metropolitan area in March 2017. Called the “Tokyo LMA,” it obtains detailed three-dimensional observations of the total lightning activity (cloud-to-ground and intracloud flashes) in storms. The network initially consisted of 8 receiving stations, expanded to 12 stations in March 2018. Real-time total lightning images were first opened on the webpage in Japan. Real-time observations from the Tokyo LMA will be used in nowcasting lightning hazards and mitigating lightning disasters. Archived data will be used to develop lightning prediction techniques and a lightning climatology for the Tokyo metropolitan area.

著者

Mikio Ishiwatari Daniel P. Aldrich Daisuke Sasaki

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.18, no.5, pp.467-474, 2023-08-01 (Released:2023-08-01)

参考文献数

43

被引用文献数

1

---

Whether national and local governments should assume larger financial responsibility for reducing disaster risk remains a controversial issue. Local governments lack resources to cover the full cost of managing mega-disasters and need assistance from higher level governments. However, national governments covering all costs may create moral hazards, discouraging local governments from investing in ex-ante measures. This study identifies national and local governments’ fiscal responsibility determinants for disaster management. Despite the differences between the federal system in the US and the centralized system in Japan, the two countries’ national governments share common practices. Both have continuously developed legislation to expand their financial responsibilities for relief and recovery efforts as disaster consequences have increased. We argue that despite major institutional differences in Japan’s unitary and the US federal government systems, both have expanded the areas covered by national assistance along with the amount over time. These findings bring with them recommendations for governments in an era of increasing extreme weather events due to climate change.

著者

Tetsuya Nakamura Satoru Masuda Akifumi Kuchiki Atsushi Maruyama

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.15, no.7, pp.991-1010, 2020-12-01 (Released:2020-12-01)

参考文献数

41

被引用文献数

3

---

In this article, we analyzed the effects of radioactive contamination from the Semipalatinsk nuclear test site on food choices in Kazakhstan. Nearly 90% of citizens in Kazakhstan knew their health had been affected by radioactive material from the nuclear test site, with more than 50% of citizens still confirming the safety of foodstuffs regarding radioactive materials when purchasing food. However, citizens in the vicinity of the nuclear test site did not take countermeasures against internal exposure due to declining fear of radioactivity, despite refraining from purchasing food from near the nuclear test site. More than 80% of Kazakhstan understood that exposure to radioactive materials was both external and internal. Further, Kazakhs were more aware of the effects of internal exposure on the human body than either Ukrainians or Japanese. Elderly people who remembered the times when nuclear tests had been conducted were aware of radioactive materials in food. High-income individuals took measures to control radioactive contamination in consideration of their nutritional balance, while low-income individuals refrained from purchasing food from near the nuclear test site as a means of controlling potential contamination. In Kazakhstan, more than 60% of citizens did not take measures against internal exposure, but the number of citizens who were concerned about radioactive materials was much higher than in either Ukraine or Japan. In Kazakhstan, 30–40% of citizens, particularly women, would buy at least 20% more if foodstuffs with lower than the regulated level of radioactive materials were sold.

著者

Akiko Sakamoto Koichi Nishiya Xuanjin Guo Airi Sugimoto Waka Nagasaki Kaito Doi

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.17, no.3, pp.327-334, 2022-04-01 (Released:2022-04-01)

参考文献数

32

被引用文献数

6

---

Of the four atoll countries in the world, the Maldives has the lowest average elevation. Therefore, it is likely to be the first country to lose its land when the sea level rises due to climate change. As a countermeasure to sea level rise, the government of the Maldives is constructing an artificial island called Hulhumalé by raising an atoll adjacent to the capital city of Malé. Other atoll countries may employ the same method to adapt to the anticipated sea level rise. There is a concern that people who are forced to relocate to the artificial island will be affected in various ways. Therefore, the purpose of this study was to identify measures to reduce the potential impacts of migration to artificial islands. This study aimed to identify factors that will work effectively to satisfy migrants from outside the Malé region to Hulhumalé. At this stage, sea level rise is not a motivating factor for migration to Hulhumalé. For the time being, enhancing high-income employment and high-level education in Hulhumalé, which are the main motivations for migration, will help sustain voluntary migration. Over the past two decades, rapid economic growth has changed the desire of Maldivians. Hulhumalé is attracting people with its new urban environment and employment opportunities. A small-scale questionnaire survey on the satisfaction level of post-migration life was conducted among the residents of Hulhumalé and the results showed that those who changed their jobs before and after migration were less satisfied with their migration than those who did not. In Hulhumalé, smart cities are being developed and new types of employment are being created. In order to facilitate the smooth migration of residents from remote islands, policies that focus on occupational changes before and after migration are needed, such as public job placement programs that enable migrants to find the same jobs that they had before migration, and job training programs that prepare them for career changes and enable them to adapt smoothly to new jobs. At present, mental health issues among migrants are not a major problem. Strengthening people-to-people networks through the use of information technology (IT) will contribute to smooth migration and resettlement.

著者

Masaki Takahashi Maya Yasui Tatsuo Kanamaru Mitsuhiro Nakagawa

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.17, no.6, pp.1080-1089, 2022-10-01 (Released:2022-10-01)

参考文献数

30

被引用文献数

1

---

The eruptive volumes and ages of the large-scale pumice eruptions of the Asama-Maekake volcano were obtained from extensive trench-based surveys. The calibrated radiocarbon age unit (CRAU) was adopted instead of each calibrated radiocarbon age. From the high-resolution tephro-stratigraphy of large-scale pumice eruptions and CRAU dating, the eruptive history of the Asama-Maekake volcano is divided into three active and two moderately active stages as follows: active stage I (9430 to 7260 ycalBP), moderately active stage 1 (7261 to 6446 ycalBP), active stage II (6447 to 3160 ycalBP), moderately active stage 2 (3161 to 1819 ycalBP), and active stage III (1820 ycalBP to present). The eruptions of the Asama-Maekake volcano consists of small-scale (phreatic to phreato-magmatic), intermediate-scale (Vulcanian), and large-scale pumice eruptions (sub-Plinian). The active stages were characterized by the occurrence of large-scale pumice eruptions. In the moderately active stages, pumice producing eruptions were lacking but instead Vulcanian eruptions dominated. A step diagram showing the relationship between eruption volumes (DRE) and ages (CRAU) is proposed, which indicates that active stage III is not time-predictable but is volume-predictable; if the large-scale pumice eruption occurs in 2022 AD, the forecasted eruptive volume is approximately 0.21 km3. The eruption rate is not constant and changes in each stage, and the average eruption rate of active stage III (0.0011 km3/year) is larger than those of active stage I (0.00006 km3/year) and II (0.0001 km3/year).

著者

Miko Maekawa Priyatma Singh Dhrishna Charan Nagisa Yoshioka Takuia Uakeia

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.14, no.9, pp.1277-1286, 2019-12-01 (Released:2019-12-01)

参考文献数

23

被引用文献数

3

---

People from Kiribati, especially after obtaining college degrees, tend to have a desire to migrate abroad to obtain further education and good jobs and, to some extent, due to the impacts of climate change. Nineteen percent of I-Kiribati migrants in Fiji who responded to our survey indicated climate change as a factor for their migration, but their primary reasons were to seek better education and employment. When seeking employment, their lack of English-language skills and professional qualifications posed challenges. However, those who had prepared well in advance tend to find jobs relatively smoothly after migration. When settling in a new area, people tended to rely on family connections, community groups, and other social supports as sources of network and safety net.

著者

Makoto Matsubara Hiroshi Sato Kenji Uehira Masashi Mochizuki Toshihiko Kanazawa

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.12, no.5, pp.844-857, 2017-10-01 (Released:2018-11-01)

参考文献数

34

被引用文献数

20

---

Tomographic analysis of the seismic velocity structure beneath oceans has always been difficult because offshore events determined by onshore seismic networks have large uncertainties in depth. In order to use reliable event locations for our computations, we have developed a method to use the hypocentral depths determined by the NIED F-net with moment tensor solutions using long-period (20-50 s) waves from offshore events away from onshore seismic networks. We applied seismic tomographic method to events occurring between the years 2000 and 2015 to generate a tomographic image of the Japanese Islands and the surrounding using travel time data picked by the NIED Hi-net, hypocenteral information for onshore earthquakes from the Hi-net, and hypocenter information for offshore events from the F-net. The seismic velocity structure at depths of 30-50 km beneath the Pacific Ocean off the east coast of northeastern Japan and onshore Japan was clearly imaged using both onshore and offshore event date. The boundary between high and low P-wave velocities (Vp) is clearly seen at the Median Tectonic Line beneath southwestern Japan at depths of 10 and 20 km. We discuss how the high-Vp lower crust and low-Vp upper crust beneath central Japan and towards the Sea of Japan are responsible for the failed rift structures formed during the opening of the Sea of Japan. Due to consequent shortening, the crustal deformation has been concentrated along the failed rift zone. Resolution of shallow structures beneath the ocean is investigated using S-net data, confirming the possibility of imaging depths of 5-20 km. In future studies, application of S-net data will be useful in evaluating whether the failed rift structure, formed during the late Cretaceous to early Tertiary, continues towards the shallow regions beneath the Pacific Ocean.

著者

Michimasa Matsumoto

出版者

Fuji Technology Press Ltd.

雑誌

Journal of Disaster Research (ISSN:18812473)

巻号頁・発行日

vol.13, no.6, pp.1125-1141, 2018-11-01 (Released:2018-11-01)

参考文献数

27

---

As of spring 2018, evacuation orders have been lifted from the entire area of Naraha Town and most of Tomioka, except for certain areas. While many evacuees have chosen their evacuation destinations as their permanent residences, some have returned to their former towns. This paper examines the factors involved in the “differentiation” and “integration” of Naraha and Tomioka residents before and after the disaster and the various forms they assume, based on the results of questionnaire surveys conducted in 2012 and 2015 as well as interviews conducted on a continuing basis since the disaster. In this process, it has become apparent that a split exists between Naraha, whose residents are moving toward “integration” with the lifting of the evacuation order, and Tomioka, whose residents are progressing toward “differentiation.”