News Article | November 29, 2016
Japanese researchers have revealed a relationship between helium levels in groundwater and the amount of stress exerted on inner rock layers of the earth, found at locations near the epicenter of the 2016 Kumamoto earthquake. Scientists hope the finding will lead to the development of a monitoring system that catches stress changes that could foreshadow a big earthquake. Several studies, including some on the massive earthquake in Kobe, Japan, in 1995, have indicated that changes to the chemical makeup of groundwater may occur prior to earthquakes. However, researchers still needed to accumulate evidence to link the occurrence of earthquakes to such chemical changes before establishing a strong correlation between the two. A team of researchers at the University of Tokyo and their collaborators found that when stress exerted on the earth's crust was high, the levels of a helium isotope, helium-4, released in the groundwater was also high at sites near the epicenter of the 2016 Kumamoto earthquake, a magnitude 7.3 quake in southwestern Japan, which caused 50 fatalities and serious damage. The team used a submersible pump in deep wells to obtain groundwater samples at depths of 280 to 1,300 meters from seven locations in the fault zones surrounding the epicenter 11 days after the earthquake in April 2016. They compared the changes of helium-4 levels from chemical analyses of these samples with those from identical analyses performed in 2010. "After careful analysis and calculations, we concluded that the levels of helium-4 had increased in samples that were collected near the epicenter due to the gas released by the rock fractures," says lead author Yuji Sano, a professor at the University of Tokyo's Atmosphere Ocean Research Institute. Furthermore, scientists estimated the amount of helium released by the rocks through rock fracture experiments in the laboratory using rock samples that were collected from around the earthquake region. They also calculated the amount of strain exerted at the sites for groundwater sample collection using satellite data. Combined, the researchers found a positive correlation between helium amounts in groundwater and the stress exertion, in which helium content was higher in areas near the epicenter, while concentrations fell further away from the most intense seismic activity. "More studies should be conducted to verify our correlation in other earthquake areas," says Sano. "It is important to make on-site observations in studying earthquakes and other natural phenomena, as this approach provided us with invaluable insight in investigating the Kumamoto earthquake," he adds. Journal article: Yuji Sano, Naoto Takahata, Takanori Kagoshima, Tomo Shibata, Tetsuji Onoue & Dapeng Zhao, "Groundwater helium anomaly reflects strain change during the 2016 Kumamoto earthquake in Southwest Japan", Scientific Reports URL: https:/ DOI: 10.1038/srep37939 Links: Atmosphere and Ocean Research Institute, The University of Tokyo Research contact: Professor Yuji Sano Atmosphere and Ocean Research Institute, The University of Tokyo 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan Tel: +81-4-7136-6100 Fax: +81-4-7136-6067 Email: firstname.lastname@example.org Press officer contact: Yoko Ogawa Press Office, Atmosphere and Ocean Research Institute, The University of Tokyo Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8564, Japan Tel: +81-4-7136-6430 Email:email@example.com Funding: This study was partly supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, under its Earthquake and Volcano Hazards Observation and Research Program. About the University of Tokyo: The University of Tokyo is Japan's leading university and one of the world's top research universities. The vast research output of some 6,000 researchers is published in the world's top journals across the arts and sciences. Our vibrant student body of around 15,000 undergraduate and 15,000 graduate students includes over 2,000 international students. Find out more at http://www. or follow us on Twitter at @UTokyo_News_en.
Komatsu T.,Kashiwanoha |
Mizuno S.,Kashiwanoha |
Natheer A.,Kashiwanoha |
Kantachumpoo A.,Kashiwanoha |
And 7 more authors.
Journal of Applied Phycology | Year: 2013
Floating seaweeds play important ecological roles in offshore waters. Recently, large amounts of rafting seaweed have been observed in the East China Sea. In early spring, juveniles of commercially important fish such as yellowtail accompany these seaweed rafts. Because the spatial distributions of seaweed rafts in the spring are poorly understood, research cruises were undertaken to investigate them in 2010, 2011, and 2012. Floating seaweed samples collected from the East China Sea during the three surveys contained only Sargassum horneri. In 2010 and 2011, seaweed rafts were distributed only in the continental shelf and the Kuroshio Front because they had become trapped in the convergence zone of the Kuroshio Front. However, in 2012, seaweed was also distributed in the Kuroshio Current and its outer waters, and massive strandings of seaweed rafts were observed on the northern coast of Taiwan and on Tarama Island in the Ryukyu Archipelago. Environmental data (wind, currents, and sea surface height) were compared among the surveys of 2010, 2011, and 2012. Two factors are speculated to have caused the unusual distribution in 2012. First, a continuous strong north wind produced an Ekman drift current that transported seaweed southwestward to the continental shelf and eventually stranded seaweed rafts on the coast of Taiwan. Second, an anticyclonic eddy covering northeast Taiwan and the Kuroshio Current west of Taiwan generated a geostrophic current that crossed the Kuroshio Current and transported the rafts to the Kuroshio Current and its outer waters. Such unusual seaweed distributions may influence the distribution of fauna accompanying the rafts. © 2013 The Author(s).
PubMed | Kashiwanoha
Type: Journal Article | Journal: Japanese journal of clinical oncology | Year: 2013
The objective of the study was to evaluate locoregional control after intensity-modulated radiotherapy for nasopharyngeal cancer using a target definition along with anatomical boundaries.Forty patients with biopsy-proven squamous cell or non-keratinizing carcinoma of the nasopharynx who underwent intensity-modulated radiotherapy between April 2006 and November 2009 were reviewed. There were 10 females and 30 males with a median age of 48 years (range, 17-74 years). More than half of the patients had T3/4 (n = 21) and/or N2/3 (n = 24) disease. Intensity-modulated radiotherapy was administered as 70 Gy/33 fractions with or without concomitant chemotherapy. The clinical target volume was contoured along with muscular fascia or periosteum, and the prescribed radiotherapy dose was determined for each anatomical compartment and lymph node level in the head and neck.One local recurrence was observed at Meckels cave on the periphery of the high-risk clinical target volume receiving a total dose of <63 Gy. Otherwise, six locoregional failures were observed within irradiated volume receiving 70 Gy. Local and nodal control rates at 3 years were 91 and 89%, respectively. Adverse events were acceptable, and 25 (81%) of 31 patients who were alive without recurrence at 2 years had xerostomia of Grade 1. The overall survival rate at 3 years was 87%.Target definition along with anatomically defined boundaries was feasible without compromise of the therapeutic ratio. It is worth testing this method further to minimize the unnecessary irradiated volume and to standardize the target definition in intensity-modulated radiotherapy for nasopharyngeal cancer.