Oita Prefecture Research Articles

大分県日田市地域の筑後川水系における泡状物質中のバイオマーカーの地球化学的特徴

大分県日田市地域の筑後川水系における泡状物質中のバイオマーカーの地球化学的特徴

Effect of polyacrylic acid on polymerization and deposition of silicic acid in geothermal water: A case study at Takigami geothermal power plant, Oita Prefecture

Effect of polyacrylic acid on polymerization and deposition of silicic acid in geothermal water: A case study at Takigami geothermal power plant, Oita Prefecture

Visualization of Potential Social Network Focusing on Common Recognition of Small Scale Distributed Geothermal Power Plant Stakeholders in Beppu City, Oita Prefecture

Visualization of Potential Social Network Focusing on Common Recognition of Small Scale Distributed Geothermal Power Plant Stakeholders in Beppu City, Oita Prefecture

愛媛県と大分県を結ぶフェリー航路利用者の交通行動分析

The Ehime and Oita prefectures are connected by three ferry routes: Yawatahama-Beppu, Misaki-Saganoseki, and Yawatahama-Usuki. The Shikoku and Kyushu islands are linked by these routes. Each route is important in various aspects such as freight and passenger transportation. Passengers especially use these routes to ply between the Shikoku and Kyusyu islands for tourism as well as business. This study aims to investigate the travel behavior of passengers, which promotes the use of these routes.

Valiability in Sediment Surface Temperature and Survival of Newly Settled Juvenile Asari （Manila）Clam, Ruditapes Philippinarum, in Nakatsu Tidal Flats, Oita Prefecture, Southwest Japan.

Valiability in Sediment Surface Temperature and Survival of Newly Settled Juvenile Asari （Manila）Clam, Ruditapes Philippinarum, in Nakatsu Tidal Flats, Oita Prefecture, Southwest Japan.

大分県尾平鉱山産水晶にみられる桜組織について

大分県尾平鉱山産水晶にみられる桜組織について

大分県の林業・林産業の新たな動き

大分県の林業・林産業の新たな動き

An investigation into the remote triggering of the Oita earthquake by the 2016 Mw 7.0 Kumamoto earthquake using full wavefield simulation

High-amplitude seismic waves from the Mw 7.0 Kumamoto earthquake of April 16, 2016, triggered another large earthquake 80 km to the NE roughly 30 s later. The source was located at shallow depths beneath the Yufuin geothermal field, Oita Prefecture, Japan, and the event magnitude was approximately 5.9. To date, this is one of the clearest known examples of a remotely triggered large earthquake. The triggered Oita event was followed by significant seismicity, which was distinct from the aftershocks of the Kumamoto earthquake. The Coulomb failure stress change around the hypocenter, calculated for the passing waves of the Kumamoto earthquake by full wavefield simulation, was about 0.7 MPa when the Oita earthquake was triggered, with the static stress change being an order of magnitude smaller. The dynamic stress changes likely played an important role in triggering. A return to low seismicity levels 1 month after the triggered earthquake may have important implications for seismic hazard due to dynamic triggering.

Earthquake early warning for the 2016 Kumamoto earthquake: performance evaluation of the current system and the next-generation methods of the Japan Meteorological Agency

The 2016 Kumamoto earthquake (Kumamoto earthquake sequence) is an extremely high-seismicity event that has been occurring across Kumamoto and Oita Prefectures in Japan since April 14, 2016 (JST). The earthquake early warning system of the Japan Meteorological Agency (JMA) issued warnings for 19 events in the Kumamoto earthquake sequence from April 14 to 19, under some of the heaviest loading conditions since the system began operating in 2007. We analyzed the system performance for cases where a warning was issued and/or strong motion was actually observed. The results indicated that the system exhibited remarkable performance, especially for the most destructive earthquakes in the Kumamoto earthquake sequence. In addition, the system did not miss or seriously under-predict strong motion of any large earthquake from April 14 to 30. However, in four cases, the system issued over-predicted warnings due to the simultaneous occurrence of small earthquakes within a short distance, which implies a fundamental obstacle in trigger-data classifications based solely on arrival time. We also performed simulations using the integrated particle filter (IPF) and propagation of local undamped motion (PLUM) methods, which JMA plans to implement to address over-prediction for multiple simultaneous earthquakes and under-prediction for massive earthquakes with large rupture zones. The simulation results of the IPF method indicated that the IPF method is highly effective at minimizing over-prediction even for multiple simultaneous earthquakes within a short distance, since it adopts a trigger-data classification using velocity amplitude and hypocenter determinations using not-yet-arrived data. The simulation results of the PLUM method demonstrated that the PLUM method is capable of issuing warnings for destructive inland earthquakes more rapidly than the current system owing to the use of additional seismometers that can only be incorporated by this method.

Ground motion estimation for the elevated bridges of the Kyushu Shinkansen derailment caused by the foreshock of the 2016 Kumamoto earthquake based on the site-effect substitution method

An earthquake of JMA magnitude 6.5 (first event) hit Kumamoto Prefecture, Japan, at 21:26 JST, April 14, 2016. Subsequently, an earthquake of JMA magnitude 7.3 (second event) hit Kumamoto and Oita Prefectures at 01:46 JST, April 16, 2016. An out-of-service Kyushu Shinkansen train carrying no passengers traveling on elevated bridges was derailed by the first event. This was the third derailment caused by an earthquake in the history of the Japanese Shinkansen, after one caused by the 2004 Mid-Niigata Prefecture Earthquake and another triggered by the 2011 Tohoku Earthquake. To analyze the mechanism of this third derailment, it is crucial to evaluate the strong ground motion at the derailment site with high accuracy. For this study, temporary earthquake observations were first carried out at a location near the bridge site; these observations were conducted because although the JMA Kumamoto Station site and the derailment site are closely located, the ground response characteristics at these sites differ. Next, empirical site amplification and phase effects were evaluated based on the obtained observation records. Finally, seismic waveforms during the first event at the bridge site of interest were estimated based on the site-effect substitution method. The resulting estimated acceleration and velocity waveforms for the derailment site include much larger amplitudes than the waveforms recorded at the JMA Kumamoto and MLIT Kumamoto station sites. The reliability of these estimates is confirmed by the finding that the same methods reproduce strong ground motions at the MLIT Kumamoto Station site accurately. These estimated ground motions will be useful for reasonable safety assessment of anti-derailment devices on elevated railway bridges.

Earthquakes in Oita triggered by the 2016 M7.3 Kumamoto earthquake

During the passage of the seismic waves from the M7.3 Kumamoto, Kyushu, earthquake on April 16, 2016, a M5.7 [semiofficial value estimated by the Japan Meteorological Agency (JMA)] event occurred in the central part of Oita prefecture, approximately 80 km far away from the mainshock. Although there have been a number of reports that M 5 triggered events. In this paper, we firstly confirm that this event is a M6-class event by re-estimating the magnitude using the strong-motion records of K-NET and KiK-net, and crustal deformation data at the Yufuin station observed by the Geospatial Information Authority of Japan. Next, by investigating the aftershocks of 45 mainshocks which occurred over the past 20 years based on the JMA earthquake catalog (JMAEC), we found that the delay time of the 2016 M5.7 event in Oita was the shortest. Therefore, the M5.7 event could be regarded as an exceptional M > 5 event that was triggered by passing seismic waves, unlike the usual triggered events and aftershocks. Moreover, a search of the JMAEC shows that in the 2016 Oita aftershock area, swarm earthquake activity was low over the past 30 years compared with neighboring areas. We also found that in the past, probably or possibly triggered events frequently occurred in the 2016 Oita aftershock area. The Oita area readily responds to remote triggering because of high geothermal activity and young volcanism in the area. The M5.7 Oita event was triggered by passing seismic waves, probably because large dynamic stress change was generated by the mainshock at a short distance and because the Oita area was already loaded to a critical stress state without a recent energy release as suggested by the past low swarm activity.

Nature-Based Tourism and Revitalization of Rural Communities in Japan: An Ethnographic Case Study of Oyama Town

This paper explores the community revitalization efforts through nature-based tourism in rural Japan. The high economic growth in the late 1980s brought a new trend of nostalgia for the countryside and a desire for rural space in domestic tourism, which went together with the demographic transition in rural Japan. Since the 1990s, many rural communities in Japan have turned towards the nature-based tourism as a ‘potential savior’ from the effects of long-term depopulation, aging, urban migration, and decreasing agricultural profitability. This paper is based on ethnographic field research in Oyama Town, located in Oita Prefecture in the southern island of Kyushu. Since the beginning of the new millennium, Oyama has embraced nature-based tourism activities in order to sustain its’ community. Oyama’s version of nature-based tourism includes themes like green tourism, landscape tourism and agriculture tourism. The research found that nature-based tourism activities in Oyama have helped the community members identify, conserve and capitalize on many latent local resources. The research also found that Oyama has succeeded in addressing the new market opportunities and acted accordingly. Nature-based tourism in Oyama has also increased the promotion of farm products and local culture, income opportunities for local women and elderly, and the diffusion of implicit knowledge on traditional rural lifestyles and environment. The findings provide an important lesson on how small communities in rural areas can be successful in sustaining their communities through community-oriented nature-based tourism, and thus have a wider signification for community revitalization in the face of extreme socio-economic transition.

Venison, another source of Paragonimus westermani infection

Paragonimiasis is a typical food-borne parasitic disease, endemic in most parts of Asia, with sporadic case reports from American and African countries. The major source of infection is undercooked freshwater crab or crayfish, though consumption of wild boar meat is also responsible for the infection in Japan, because wild boar is a paratenic host for Paragonimus westermani. Recently, living juveniles of P. westermani were isolated from muscle of a sika deer, Cervus nippon, in Japan, raising the possibility that venison has been another source of infection. In order to clarify the potential contribution of venison consumption to the occurrence of paragonimiasis, we analysed dietary histories of those paragonimiasis patients in whose diagnoses we were involved between 2001 and 2015. Among 380 patients, freshwater crab had been consumed by 208 patients, wild boar meat by 190, and wild deer meat by 76 patients before the onset of the disease. Overall contribution of wild deer meat was estimated to be 6.8% to 20.0%, although in Oita and Gifu Prefectures, where a substantial proportion of patients had consumed raw venison, the contribution of venison consumption was much higher (27.5 to 62.1% and 42.1 to 78.9% in Oita and Gifu Prefectures, respectively). We demonstrated P. westermani-specific antibodies in the sera of 4 out of 160 sika deer from Gifu Prefecture, strongly suggesting that these deer were infected with P. westermani.

Autonomous evacuation and local community

Purpose The Aso area of Kumamoto Prefecture and the western part of Oita Prefecture in Japan experienced heavy rainfall from midnight until morning on 12 July 2012. Flooding and landslides caused by this torrential rain killed 31 people and injured 11. This paper aims to analyze a time series of flood risk perception and evacuation behavior, and to identify factors that promote effective autonomous evacuation. Design/methodology/approach A time series of flood risk perception and evacuation behavior following the 2012 flood was developed and systematically analyzed. Differences between the data sets (compiled from survey data) for the evacuated group and the non-evacuated group were statistically evaluated. Then, an evacuation behavior model was developed to simulate which households would be likely to evacuate in different scenarios. The relationship between disaster prevention and activities of a local community were also statistically assessed. Findings This study concludes that an assessment of river conditions and evacuation advice from fellow local community members are the factors that most strongly influence and promote autonomous evacuation. This study also revealed that the everyday activities of a local community have the potential to foster effective disaster prevention and emergency responses if they promote the building of relationships between community members. Originality/value The research focused on actual decision-making and autonomous evacuation behavior. Whereas previous studies were limited to the analysis of activities of disaster prevention on a normal day, this study proved that the usual activity level in local community activities and relationships significantly affected evacuation behavior.

Origins of recently re‐established and newly discovered populations of the endangered butterfly Shijimiaeoides divinus (Lepidoptera: Lycaenidae) in Oita Prefecture, Japan

AbstractThe endangered butterfly Shijimiaeoides divinus was believed to have been extirpated from Oita Prefecture, Kyushu, Japan, but was rediscovered in Taketa in recent years. This population is considered to have re‐established as a result of natural dispersal from Kumamoto, a neighboring prefecture located to the west of Oita. Furthermore, another population was recently found in Yufu, Oita Prefecture, which is an area where the species had never been recorded. To elucidate the origins of these two populations newly found from Oita Prefecture, their DNA sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene were compared with those of other S. divinus populations from Kumamoto Prefecture, Honshu and Korea. The results supported the hypothesis that the Taketa population originated from Kumamoto Prefecture. However, it was not clear whether this population originated from the natural dispersal or deliberate release of individuals. It was also found that the Yufu population was not established by the deliberate release of individuals from Honshu or Korea; however, it remained unclear whether the population of S. divinus was native to Yufu, or originated from other localities in Kyushu.

Stratigraphy and radiolarian ages of stratiform manganese deposits from the Chichibu Belt in the Saiki area, eastern Oita Prefecture, Japan

Stratigraphy and radiolarian ages of stratiform manganese deposits from the Chichibu Belt in the Saiki area, eastern Oita Prefecture, Japan

Perception of Radiation Risk by Japanese Radiation Specialists Evaluated as a Safe Dose Before the Fukushima Nuclear Accident.

From October to December 2010, just before the radiological accident at the Fukushima Daiichi nuclear power plant, 71 radiation professionals from radiation facilities in Japan were asked what they considered as a "safe dose" of radiation for themselves, their partners, parents, children, siblings, and friends. Although the 'safe dose' they noted varied widely, from less than 1 mSv y to more than 100 mSv y, the average dose was 35.6 mSv y, which is around the middle point between the legal exposure dose limits for the annual average and for any single year. Similar results were obtained from other surveys of members of the Japan Radioisotope Association (36.9 mSv y) and of the Oita Prefectural Hospital (36.8 mSv y). Among family members and friends, the minimum average "safe" dose was 8.5 mSv y for children, for whom 50% of the responders claimed a "safe dose" of less than 1 mSv. Gender, age and specialty of the radiation professional also affected their notion of a "safe dose." These findings suggest that the perception of radiation risk varies widely even for radiation professionals and that the legal exposure dose limits derived from regulatory science may act as an anchor of safety. The different levels of risk perception for different target groups among radiation professionals appear similar to those in the general population. The gap between these characteristics of radiation professionals and the generally accepted picture of radiation professionals might have played a role in the state of confusion after the radiological accident.

3．大分県・竹田市での救急要請例における入浴関連事故の検討

3．大分県・竹田市での救急要請例における入浴関連事故の検討

Epidemiologic Research on Malformations Associated with Cleft Lip and Cleft Palate in Japan.

To investigate malformations associated with cleft lip and cleft palate, we conducted surveys at neonatal intensive care units (NICUs) and other non-NICU facilities and to determine whether there are differences among facilities. The regional survey investigated NICU facilities located in Oita Prefecture, including 92 patients with cleft lip and palate (CLP) or cleft palate (CP) that occurred between 2004 and 2013, and the national survey investigated oral surgery, plastic surgery, and obstetrics and gynecology facilities located in Japan, including 16,452 patients with cleft lip (CL), CLP, or CP that occurred since 2000. The incidence per 10,000 births was 4.2, 6.2, and 2.8 for CL, CLP, and CP, respectively, according to the national survey, and 6.3 and 2.9 for CLP and CP, respectively according to the regional survey. These results indicated comparable incidences between the two surveys. In contrast, when the survey results on malformations associated with CLP and CP according to the ICD-10 classification were compared between the national survey conducted at oral surgery or plastic surgery facilities and the regional survey conducted at NICU facilities, the occurrence of associated malformations was 19.8% vs. 41.3% for any types of associated malformation, 6.8% vs. 21.7% for congenital heart disease, and 0.5% vs. 16.3% for chromosomal abnormalities. These results indicated that the incidences of all of these associated malformations were significantly greater in the survey conducted at NICU facilities and similar to the findings from international epidemiological surveys. When comparing the survey conducted at obstetrics facilities vs. NICU facilities, the occurrence of associated malformations was similar results as above. The incidence of CLP and CP was not different between surveys conducted at NICU facilities vs. non-NICU facilities; however, when conducting surveys on associated malformations, it is possible to obtain accurate epidemiological data by investigating NICU facilities where detailed examinations are thoroughly performed.

Hot spring drainage impact on fish communities around temperate estuaries in southwestern Japan

Study regionWe investigated in Beppu, Oita Prefecture, Japan. Hot spring drainage flows into a river and then flows into coastal areas in this area, a region in Japan with many hot springs. Study focusThe effects of that drainage on river and coastal area ecosystems remain unclear. We evaluated the impact of the hot spring drainage on fish communities near the estuary. New hydrological insightsFactor analysis results obtained using water quality data show that the scale of the hot spring drainage influence on rivers differs among rivers. The inflow of hot spring drainage into the rivers affects phytoplankton more than the inflow of domestic drainage, which increases the amount of phytoplankton. Furthermore, hot spring drainage creates a better habitat for Nile tilapia, a foreign species, by increasing food availability and water temperature.