著者
JongEun Yim
出版者
Tohoku University Medical Press
雑誌
The Tohoku Journal of Experimental Medicine (ISSN:00408727)
巻号頁・発行日
vol.239, no.3, pp.243-249, 2016 (Released:2016-07-16)
参考文献数
60
被引用文献数
38 85

In modern society, fierce competition and socioeconomic interaction stress the quality of life, causing a negative influence on a person’s mental health. Laughter is a positive sensation, and seems to be a useful and healthy way to overcome stress. Laughter therapy is a kind of cognitive-behavioral therapies that could make physical, psychological, and social relationships healthy, ultimately improving the quality of life. Laughter therapy, as a non-pharmacological, alternative treatment, has a positive effect on the mental health and the immune system. In addition, laughter therapy does not require specialized preparations, such as suitable facilities and equipment, and it is easily accessible and acceptable. For these reasons, the medical community has taken notice and attempted to include laughter therapy to more traditional therapies. Decreasing stress-making hormones found in the blood, laughter can mitigate the effects of stress. Laughter decreases serum levels of cortisol, epinephrine, growth hormone, and 3,4-dihydrophenylacetic acid (a major dopamine catabolite), indicating a reversal of the stress response. Depression is a disease, where neurotransmitters in the brain, such as norepinephrine, dopamine, and serotonin, are reduced, and there is something wrong in the mood control circuit of the brain. Laughter can alter dopamine and serotonin activity. Furthermore, endorphins secreted by laughter can help when people are uncomfortable or in a depressed mood. Laughter therapy is a noninvasive and non-pharmacological alternative treatment for stress and depression, representative cases that have a negative influence on mental health. In conclusion, laughter therapy is effective and scientifically supported as a single or adjuvant therapy.
著者
Maya KAMAO Yoshitomo SUHARA Naoko TSUGAWA Masako UWANO Noriko YAMAGUCHI Kazuhiro UENISHI Hiromi ISHIDA Satoshi SASAKI Toshio OKANO
出版者
Center for Academic Publications Japan
雑誌
Journal of Nutritional Science and Vitaminology (ISSN:03014800)
巻号頁・発行日
vol.53, no.6, pp.464-470, 2007 (Released:2008-01-18)
参考文献数
32
被引用文献数
55 118

Several reports indicate an important role for vitamin K in bone health as well as blood coagulation. However, the current Adequate Intakes (AI) might not be sufficient for the maintenance of bone health. To obtain a closer estimate of dietary intake of phylloquinone (PK) and menaquinones (MKs), PK, MK-4 and MK-7 contents in food samples (58 food items) were determined by an improved high-performance liquid chromatography method. Next, we assessed dietary vitamin K intake in young women living in eastern Japan using vitamin K contents measured here and the Standard Tables of Food Composition in Japan. PK was widely distributed in green vegetables and algae, and high amounts were found in spinach and broccoli (raw, 498 and 307 μg/100 g wet weight, respectively). Although MK-4 was widely distributed in animal products, overall MK-4 content was lower than PK. MK-7 was observed characteristically in fermented soybean products such as natto (939 μg/100 g). The mean total vitamin K intake of all subjects (using data from this study and Japanese food composition tables) was about 230 μg/d and 94% of participants met the AI of vitamin K for women aged 18-29 y in Japan, 60 μg/d. The contributions of PK, MK-4 and MK-7 to total vitamin K intake were 67.7, 7.3 and 24.9%, respectively. PK from vegetables and algae and MK-7 from pulses (including fermented soybean foods) were the major contributors to the total vitamin K intake of young women living in eastern Japan.
著者
新井 康通 広瀬 信義 川村 昌嗣 本間 聡起 長谷川 浩 石田 浩之 小薗 康範 清水 健一郎 中村 芳郎 阪本 琢也 多田 紀夫 本間 昭
出版者
一般社団法人 日本老年医学会
雑誌
日本老年医学会雑誌 (ISSN:03009173)
巻号頁・発行日
vol.34, no.3, pp.202-208, 1997-03-25 (Released:2009-11-24)
参考文献数
22
被引用文献数
3 5

東京都在住の百寿者45名 (男15例, 女30例, 平均年齢101.1±1.4歳, mean±SD, 以下同じ) の血清脂質値, アポ蛋白A1 (以下アポA1と略す), アポ蛋白B (以下アポBと略す), リポ蛋白分画, 低比重リポ蛋白 (以下LDLと略す) 分画の被酸化能を測定し, 健常な若年対照群と比較検討した.百寿者では対照群に比べ, 総コレステロール (以下TCと略す), 高比重リポ蛋白コレステロール (以下HDL-Cと略す), アポA1, アポBが有意に低値を示した. アポBが60mg/dl以下の低アポB血症の頻度は対照群の2.3%に対し, 百寿者では23%と有意に高かった. 各リポ蛋白分画中のコレステロール濃度は超低比重リポ蛋白コレステロール (以下VLDL-Cと略す), LDL-C, HDL-C, のいずれにおいても百寿者で有意に低かった. HDLの亜分画を比べると百寿者で低下していたのはHDL3-Cであり, 抗動脈硬化作用を持つHDL2-Cは両群で差がなく, 百寿者の脂質分画中に占めるHDL2-Cの割合は有意に増加していた. LDLの被酸化能の指標である lag time には有意差を認めなかった (百寿者44.7分±31.8対対照群49.9±26.0分). 百寿者を日常生活動度 (以下ADLと略す) の良好な群と低下している群に分け, 脂質パラメータを比較したところ, ADLが良好な群でHDL3-Cが有意に高値を示していた. 認知機能を Clinical Dementia Rating (以下CDRと略す) によって正常から重度痴呆まで5段階に評価し, 各群の脂質パラメータを比較したところ, 中等度以上の痴呆群でHDL-Cが正常群に比べ有意に低下していた.百寿者はアポBが低く, HDL2-Cが比較的高値であり, 遺伝的に動脈硬化を促進しにくい脂質組成を示すことが明らかとなった.
著者
Xiaolu FENG Jincai LU Hailiang XIN Lei ZHANG Yuliang WANG Kexuan TANG
出版者
The Pharmaceutical Society of Japan
雑誌
YAKUGAKU ZASSHI (ISSN:00316903)
巻号頁・発行日
vol.131, no.3, pp.423-429, 2011-03-01 (Released:2011-03-01)
参考文献数
25
被引用文献数
19 31

The aim of this study was to ascertain the anti-arthritic active fraction of Capparis spinosa L. (Capparidaceae) fruits and its chemical constituents. The adjuvant arthritic rat model was developed to evaluate the anti-arthritic effects of different fractions of ethanol extraction from C. spinosa L. The fraction eluted by ethanol-water (50:50, v/v) had the most significant anti-arthritic activity. The chemical constituents of this fraction were therefore studied; seven known compounds were isolated and identified as: (1) P-hydroxy benzoic acid; (2) 5-(hydroxymethyl) furfural; (3) bis (5-formylfurfuryl) ether; (4) daucosterol; (5) α-D-fructofuranosides methyl; (6) uracil; and (7) stachydrine.
著者
Hirotoshi UTSUNOMIYA Tadashi YAMAKAWA Junzo KAMEI Kazuaki KADONOSONO Shun-Ichi TANAKA
出版者
バイオメディカルリサーチプレス
雑誌
Biomedical Research (ISSN:03886107)
巻号頁・発行日
vol.26, no.5, pp.193-200, 2005 (Released:2005-12-05)
参考文献数
30
被引用文献数
11 24

Dried plums, considered a healthy food in the West and used as medicine in India, contain phenolic compounds with protective actions against age-related diseases. Effects of oral plum ekisu (concentrated juice) on lipid and glucose tolerance were assessed in insulin-resistant obese Wistar fatty rats. Plum ingestion decreased blood glucose (P < 0.05) and plasma triglyceride concentrations (P < 0.01) compared with controls. Plum treatment for 2 weeks reduced areas under the curve (AUCs) for glucose and insulin during a glucose tolerance test. In db/db mice, plum decreased these AUCs, and also blood glucose during an insulin tolerance test. Plum treatment significantly increased plasma adiponectin concentrations and PPARγ mRNA expression in adipose tissue from Wistar fatty rats. Plum thus may increase insulin sensitivity in these rats via adiponectin-related mechanisms.
著者
大久保 修三 黒川 忠英 鈴木 徹 船越 将二 辻井 禎
出版者
日本貝類学会
雑誌
貝類学雑誌 (ISSN:00423580)
巻号頁・発行日
vol.56, no.3, pp.259-269, 1997
参考文献数
28

Generation of the streak-like flash in the inner-fold of the mantle in Ctenoides ales was investigated by video-camera recording, and stereo, light, fluorescence and electron microscopy. The stereo microscopy revealed the presence of a pale white band along the entire width of the marginal edge of the shell side surface of the inner fold. Since the flashing could not be seen in the dark, it was not due to the luminescence but the reflection of light. The light microscopy showed that the band region consisted of about ten rows of epithelial cells, cylindrical and 40 μm tall and 10 μm wide. The cytoplasm was densely filled with fine granules, eosinophilic in H-E staining. Under the electron microscope, those granules appeared as electron-dense vesicles, 0.5-0.6 μm in diameter, each containing a highly electron-dense spherical core, 0.2-0.3 μm in diameter. The cell had a nucleus, few mitochondria and lysosomes, however, other cellular organelles such as Golgi apparatus, rough and smooth endoplasmic reticulum were not evident, in the present observation. We assume that the electron-dense vesicles packed in the cytoplasm function to reflect light strongly. This highly reflecting structure found in C. ales is quite different from those have been reported in eyes of scallop and squid, and in iridophores of giant clam, cuttlefish, long-spined sea urchin and of fishes. The video observation showed that the mantle made a movement to roll the white band towards the shell-side and then, within a second, the rolling movement was released. The phase of the movement was different by the portions of the mantle, and the mantle edge made a wave-like motion. When the pale white band was hidden by the roll, the reflection of light disappeared. When the rolling was released, the reflection of light reappeared. Since the "roll and release movement" repeat quickly, it looks as though a streak-like flash run along the mantle margin.
著者
高田 知紀 梅津 喜美夫 桑子 敏雄
出版者
公益社団法人 土木学会
雑誌
土木学会論文集F6(安全問題) (ISSN:21856621)
巻号頁・発行日
vol.68, no.2, pp.I_167-I_174, 2012 (Released:2013-01-30)
参考文献数
32
被引用文献数
1 10 5

東日本大震災では,多くの神社が津波被害を免れたことが指摘されている.本研究では,日本の神社に祀られる祭神の多様性は,人びとの関心に応じた差異化の結果であるという仮説から,宮城県沿岸部の神社についてその祭神と空間的配置に着目しながら被害調査を行った.祭神については特に,ヤマタノオロチ退治で知られるスサノオノミコトに着目した.スサノオは無病息災の神として祀られることから,洪水や津波といった自然災害時にも大きな役割を果たすと考えられる.また,地域の治水上の要所に鎮座していることが多い.東北での調査から,スサノオを祀った神社,またスサノオがルーツであると考えられる熊野神社は,そのほとんどが津波被害を免れていることを明らかにした.この結果は,地域の歴史や文化をふまえたリスク・マネジメントのあり方について重要な知見を提供する.
著者
Seiji Yukimoto Kunihiko Kodera Rémi Thiéblemont
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.13, pp.53-58, 2017 (Released:2017-04-04)
参考文献数
29
被引用文献数
8

A delayed response of the winter North Atlantic oscillation (NAO) to the 11-year solar cycle has been observed and modeled in recent studies. However, the mechanisms creating this 2-4-year delay to the solar cycle have still not been well-understood. This study examines the effects of the 11-year solar cycle and the resulting modulation in the strength of the winter stratospheric polar vortex. A coupled atmosphere–ocean general circulation model is used to simulate these effects by introducing a mechanistic forcing in the stratosphere. The intensified stratospheric polar vortex is shown to induce positive and negative ocean temperature anomalies in the North Atlantic Ocean. The positive ocean temperature anomaly migrated northward and was amplified when it approached an oceanic frontal zone approximately 3 years after the forcing became maximum. This delayed ocean response is similar to that observed. The result of this study supports a previous hypothesis that suggests that the 11-year solar cycle signals on the Earth's surface are produced through a downward penetration of the changes in the stratospheric circulation. Furthermore, the spatial structure of the signal is modulated by its interaction with the ocean circulation.
著者
Koji Tamakoshi Hideaki Toyoshima Hiroshi Yatsuya Kunihiro Matsushita Tomonori Okamura Takehito Hayakawa Akira Okayama Hirotsugu Ueshima The NIPPON DATA90 Research Group
出版者
日本循環器学会
雑誌
Circulation Journal (ISSN:13469843)
巻号頁・発行日
vol.71, no.4, pp.479-485, 2007 (Released:2007-03-25)
参考文献数
23
被引用文献数
24 52

Background The association of white blood cell (WBC) count with all-cause and cardiovascular disease (CVD) mortality were examined in the National Integrated Project for Prospective Observation of Non-communicable Disease and Its Trends in the Aged (NIPPON DATA) 90. Methods and Results A total of 6,756 Japanese residents (2,773 men and 3,983 women) throughout Japan without a history of CVD were followed for 9.6 years. A Cox proportional hazards regression model was used to estimate the relative risk (RR) and 95% confidence interval (CI). We documented 576 deaths with 161 deaths from CVD. Overall, after adjusting for several confounders including age, sex, body mass index at baseline, smoking status, alcohol consumption, regular exercise, diastlic blood pressure, total cholesterol, high-density lipoprotein-cholesterol and hemoglobin A1c, a graded association between WBC count and higher risk of all-cause mortality was observed (WBC of 9,000-10,000 cells/mm3 vs WBC of 4,000-4,900: RR =1.61, 95% CI: 1.07-2.40, p for trend =0.02). Elevated WBC count was almost significantly associated with high risk of CVD mortality (WBC of 9,000-10,000 vs WBC of 4,000-4,900: RR =1.79, 95% CI: 0.97-3.71). These associations strengthened among women. Stratified by smoking status, never-smokers with WBC counts of 9,000-10,000 had a 3.2 fold elevated risk for CVD death compared with those with WBC counts of 4,000-4,900. Conclusions The WBC count may have potential as a predictor for all-cause mortality, particularly CVD mortality. (Circ J 2007; 71: 479 - 485)
著者
Yasuoka Koichi Yasuoka Motoko
出版者
Institute for Research in Humanities Kyoto University
雑誌
ZINBUN (ISSN:00845515)
巻号頁・発行日
vol.42, pp.161-174, 2011-03

QWERTY keyboard is widely used for information processing nowadays in Japan, United States, and other countries. And the most frequently asked question about the keyboard is: “Why are the letters of the keyboard arranged the way they are?” Several papers in the field of information processing answer the question like this: “To slow down the operator.” It’s nonsense. In this paper we reveal the prehistory of QWERTY keyboard along the history of telegraph apparatus: Morse, Hughes-Phelps, and Teletype. The early keyboard of Type-Writer was derived from Hughes-Phelps Printing Telegraph, and it was developed for Morse receivers. The keyboard arrangement very often changed during the development, and accidentally grew into QWERTY among the different requirements. QWERTY was adopted by Teletype in the 1910’s, and Teletype was widely used as a computer terminal later.
著者
Yuta Katori Kan Okubo
出版者
The Institute of Electronics, Information and Communication Engineers
雑誌
IEICE Communications Express (ISSN:21870136)
巻号頁・発行日
vol.7, no.10, pp.352-357, 2018 (Released:2018-10-01)
参考文献数
12
被引用文献数
2

For years, researchers have been studying the relation between earthquakes and geomagnetic field signals using observation results. Following our continuous geomagnetic observation, this report describes geomagnetic signal changes generated by earthquakes and tsunami waves. Results show that detection of their occurrence using geomagnetic field measurement is effective for providing an early alarm system for disaster mitigation. Robust detection requires the robust estimation of a geomagnetic field using multiple observation results. This study introduced a deep neural network (DNN) to estimate geomagnetic fields. Results clarified that the proposed DNN model using data of multiple axes at multiple observation points as input data provides efficient solutions for geomagnetic estimation.
著者
Chitose Ishikawa Takayoshi Tsutamoto Masanori Fujii Hiroshi Sakai Toshinari Tanaka Minoru Horie
出版者
日本循環器学会
雑誌
Circulation Journal (ISSN:13469843)
巻号頁・発行日
vol.70, no.7, pp.857-863, 2006 (Released:2006-06-25)
参考文献数
31
被引用文献数
36 50

Background The prognostic role of serum C-reactive protein (CRP) in chronic heart failure (CHF) patients, especially those with nonischemic dilated cardiomyopathy (DCM), remains unknown. In the present study, whether CRP provides prognostic information in DCM patients was evaluated. Methods and Results Neurohumoral factors and hemodynamics in 84 consecutive DCM patients were measured and these patients were followed up for a mean period of 42 months. During the follow-up period, 23 patients developed cardiac events and 18 patients died of cardiac causes. Using stepwise multivariate Cox proportional hazards regression analyses, log brain natriuretic peptide (BNP) (p=0.007) and high-sensitivity CRP (hsCRP) >1 mg/L (p=0.008) were significant independent predictors of cardiac events. The patients were stratified into 4 groups based on the normal serum concentration of hsCRP (1 mg/L) and median plasma concentration of BNP (110 pg/ml). Survival rates were significantly higher in patients with hsCRP <1 mg/L and BNP <110 pg/ml. The hazard ratio of patients with BNP >110 pg/ml and hsCRP >1 mg/L was 15.8 (95% confidence interval, 1.9-127.2) compared with those with BNP <110 pg/ml and hsCRP <1 mg/L for cardiac death. Conclusions Serum hsCRP level is an independent prognostic predictor in patients with DCM and the combination of hsCRP and BNP may be useful for the management of CHF patients with DCM. (Circ J 2006; 70: 857 - 863)
著者
上田 浩 石井 良和 外村 孝一郎 植木 徹
出版者
情報処理学会
雑誌
情報処理学会研究報告[教育学習支援情報システム] (ISSN:21888620)
巻号頁・発行日
vol.2015-CLE-16, no.9, pp.1-8, 2015-05-15

SIG Technical Reports are nonrefereed and hence may later appear in any journals, conferences, symposia, etc.
著者
Satoshi Yamaori Yoshimi Okushima Kazufumi Masuda Mika Kushihara Takashi Katsu Shizuo Narimatsu Ikuo Yamamoto Kazuhito Watanabe
出版者
公益社団法人日本薬学会
雑誌
Biological and Pharmaceutical Bulletin (ISSN:09186158)
巻号頁・発行日
vol.36, no.7, pp.1197-1203, 2013-07-01 (Released:2013-07-01)
参考文献数
39
被引用文献数
2 15

Our recent work has shown that cannabidiol (CBD) exhibits the most potent direct inhibition of human cytochrome P450 1A1 (CYP1A1) among the CYP enzymes examined. However, the mechanism underlying this CBD inhibition remains to be clarified. Thus, to elucidate the structural requirements for the potent inhibition by CBD, the effects of CBD and its structurally related compounds on CYP1A1 activity were investigated with recombinant human CYP1A1. Olivetol, which corresponds to the pentylresorcinol moiety of CBD, inhibited the 7-ethoxyresorufin O-deethylase activity of CYP1A1; its inhibitory effect (IC50=13.8 µM) was less potent than that of CBD (IC50=0.355 µM). In contrast, d-limonene, which corresponds to the terpene moiety of CBD, only slightly inhibited CYP1A1 activity. CBD-2′-monomethyl ether (CBDM) and CBD-2′,6′-dimethyl ether inhibited CYP1A1 activity with IC50 values of 4.07 and 23.0 µM, respectively, indicating that their inhibitory effects attenuated depending on the level of methylation on the free phenolic hydroxyl groups in the pentylresorcinol moiety of CBD. Cannabidivarin inhibited CYP1A1 activity, although its inhibitory potency (IC50=1.85 µM) was lower than that of CBD. The inhibitory effects of Δ9-tetrahydrocannabinol and cannabielsoin (IC50s ≈10 µM), which contain a free phenolic hydroxyl group and are structurally constrained, were less potent than that of CBDM, which contains a free phenolic hydroxyl group and is rotatable between pentylresorcinol and terpene moieties. These results suggest that the pentylresorcinol structure in CBD may have structurally important roles in direct CYP1A1 inhibition, although the whole structure of CBD is required for overall inhibition.
著者
高橋 達也 藤盛 啓成 山下 俊一 齋藤 寛
出版者
長崎大学
雑誌
基盤研究(C)
巻号頁・発行日
2000

1993年から1997年まで、マーシャル諸島甲状腺研究(The Marshall Islands Nationwide Thyroid DiseaseStudy)によって、現地で医学的・疫学調査が行われた。マーシャル諸島住民では、甲状腺結節性病変の有病率が高かった。甲状腺結節の最も一般的な形態は、腺腫様甲状腺腫(adenomatous goiter)であった。しかしながら、本研究で発見された腺腫様甲状腺腫の患者の多くは、医学的治療を必要としなかった。幾多の他の研究と同じように、女性では、男性と比較して甲状腺結節の有病率が高かった。また、有病率は、年齢とともに高くなり、50歳代の女性で最も高率(約50%)であった。甲状腺結節例の約半数は、触診で診断できたが、残りの半数は、超音波診断によってのみ診断し得た(触診できなかった)。甲状腺機能低下症や甲状腺亢進症(バセドウ病)の様な甲状腺機能の異常は、マーシャル諸島では、比較的まれで、有病率は他国と比較して同程度、もしくは、低かった。太平洋地域(日本を含む)などに多く見られる橋本病(自己免疫性甲状腺炎)は、マーシャル諸島では、まれであった。甲状腺癌の疑いで43人の患者が、現地のマジェロ病院において、マーシャル諸島甲状腺研究の医療チームによってなされた手術を受けた。この43人中、25人については、病理学的に癌が確認された。外科手術で重篤な合併症は、1人も発生しなかった。マーシャル諸島全体での、一般住民の甲状腺結節や甲状腺癌の頻度は、従来報告されているよりもかなり高かった。しかし、我々は、ハミルトン博士(Dr.Hamilton)の仮説、すなわち、「甲状腺結節の頻度は、ブラボー実験の時に住んでいた場所とビキニ環礁からの距離に反比例する(ビキニから遠くなると、結節は減る)」、を確認できなかった。この点に関して、ブラボー実験で被曝した住民における甲状腺癌の頻度に関する予備的な分析では、概算した甲状腺放射線被曝量と甲状腺癌有病率は正の相関(被曝量が増えると甲状腺癌も増える)が有意に示された。
著者
高井 良尋 山田 章吾
出版者
東北大学
雑誌
一般研究(C)
巻号頁・発行日
1992

現在までに低線量全身(ないし体幹)照射(low dose total body(or trunk)irradiation:以下L-TBI)が行われた症例は89例となり、ある程度症例が集積されたためL-TBIの適応症例の検討が可能となった。89例の内訳は非ホジキンリンパ腫50例(うち32例は新鮮症例)、固形腫瘍などが39例である。L-TBI単独の抗腫瘍効果が評価できるL-TBI先行例(局所照射後でも転移巣などの評価可能病巣のある症例も含む)は非ホジキンリンパ腫新鮮症例13例、再燃症例13例、固形腫瘍など17例であった。奏効率はそれぞれ85%,23%,18%であり、非ホジキンリンパ腫新鮮例に対してはきわめて良好であったが、再燃例や、固形腫瘍などはL-TBI単独での効果は期待できない結果となっている。固形腫瘍などPR3例のうち2例はリンパ系腫瘍のホジキンリンパ腫2例であり、真の固形癌ではL-TBI単独ではほとんど抗腫瘍効果はないと思われる。非ホジキンリンパ腫再燃例では、以前に根治的な化学療法の行われていない、免疫機構の荒廃していない症例でのみL-TBI単独の効果が認められており、2,3次以上の再燃例で化学療法が何度も行われていた症例ではすべてNCかPDであり、L-TBI単独の効果は期待できない。非ホジキンリンパ腫の新鮮例に対しては極めて有効で、局所照射と化学療法の上にL-TBIをアジュバンドとして使用したI,II期患者の5年生存率は、histrical control群に比し有意に有効であった。固形癌では新鮮例の局所照射と併用することにより局所制御率向上と遠隔転移抑制に期待できるがこれに対する答えはこの3年間では出せない。今後の課題である。末梢血リンパ球サブセット分画の解析ではヘルパーT、ヘルパーインデューサーT細胞分画に有意な増加またサプレッサーT細胞の有意傾向のある減少を認めたことよりL-TBIの抗腫瘍効果の一つは細胞性免疫の賦活効果であることは間違いない。体幹部照射で鼻腔原発のリンパ腫がCRとなった症例を認めたことは特筆に値する。
著者
Jonny Wu John Suppe Renqu Lu Ravi V.S. Kanda
出版者
日本地球惑星科学連合
雑誌
JpGU-AGU Joint Meeting 2017
巻号頁・発行日
2017-03-10

Seismic tomography has revealed enigmatic stagnant slab anomalies under Japan, Korea and NE China (i.e. the Japan slab). The stagnant slabs flatten near the mantle transition zone around ~410 to 660 km depths and extend >2000 km westward from the NW Pacific subduction zones. The location of the outboard stagnant slabs far inland under Eurasia cannot be explained by slab rollback alone and pose a challenge to our current understanding of subducted slab dynamics, in which slabs sink vertically over time with minimal lateral motion.In this study, we use new and recently published 3D slab mapping, slab unfolding and plate reconstruction constraints (Wu et al., 2016, JGR) from MITP08 and GAP_P4 global tomography (Li et al., 2008, G3; Fukao et al., 2013, JGR). We show that the Japan stagnant slabs are best reconstructed as Pacific slabs that subducted in the Cenozoic after Pacific-Izanagi ridge subduction between 60 to 50 Ma. Mantle flow forward models reproduce our Japan slab reconstruction results (Seton et al., 2015, GRL). Our reconstruction implies the Japan slabs moved laterally westwards within the upper mantle and transition zone after subduction at near-plate tectonic rates (~2 cm/yr over 50 Ma), indicating a greater lateral mobility of slabs within the upper mantle and transition zone than previously recognized.Using our Japan slab subduction model, we re-examine the enigmatic Vityaz deep earthquakes under the Fiji Basin, which are widely thought to be a globally-unique case of seismicity within a foundered and detached slab. Our Tonga slab mapping shows the Vityaz earthquakes are actually part of a >2500 km-long mega-Wadati-Benioff zone of the northern Tonga stagnant slab. Our slab reconstruction suggests the northern Tonga slab moved laterally westward in a similar fashion to the Japan slabs, but at a faster rate of >5 cm/yr over 15 Ma within the upper ~660 km. Our results suggest that earthquakes can be produced thousands of kilometers away from a subduction zone from lateral movements of still-attached but mobile stagnant slabs within the uppermost ~660 km mantle.