著者

Miyazawa Masatoshi

出版者

American Geophysical Union

雑誌

Geophysical Research Letters (ISSN:00948276)

巻号頁・発行日

vol.38, 2011-12

被引用文献数

56

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Increases in seismicity have been widely observed at varying distances from the source area following large earthquakes. The increased number of earthquakes are usually called aftershocks if the area is within a rupture length of the mainshock, and called remotely triggered events if they are well beyond that distance. These earthquakes can be explained as being induced by static and/or dynamic stress changes due to the mainshock. However, clear observations of dynamic triggering have been inadequate to differentiate between the two mechanisms. This study shows that early post-seismic events triggered by the 2011 M(w) 9.0 Tohoku-Oki earthquake systematically propagated over Japan in a southwestern direction, associated with the strong seismic waves from the source. The propagation front was consistent with the arrivals of large amplitude surface waves traveling at 3.1 to 3.3 km/s and extending to a distance of 1, 350 km. There were no observations of triggered earthquakes in the northern direction. Dynamic stress changes toward the north were comparable to or smaller than those necessary for triggering in the southwestern direction. Static stress changes were one to two orders smaller than dynamic stress changes at remote distance, indicating that static stress was not the main mechanism of the triggering. Furthermore, the dynamic stress/strain changes play an important role for remote triggering if the value is more than ∼500 kPa in stress or ∼10[−6] in strain.

著者

Ebihara Y. Tanaka T.

出版者

American Geophysical Union

雑誌

Journal of Geophysical Research: Space Physics (ISSN:21699402)

巻号頁・発行日

vol.120, no.12, pp.10466-10484, 2015-12-21

被引用文献数

37

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オーロラ爆発はなぜ起こるのか? --スーパーコンピューターでオーロラ爆発の基本的な仕組みを明らかに--. 京都大学プレスリリース. 2015-12-21.

著者

Aoki S. Kobayashi R. Rintoul S. R. Tamura T. Kusahara K.

出版者

American Geophysical Union

雑誌

Journal of Geophysical Research Oceans (ISSN:21699275)

巻号頁・発行日

vol.122, no.8, pp.6277-6294, 2017-08-13

著者

Yi Shuang Sun Wenke Heki Kosuke Qian An

出版者

American Geophysical Union

雑誌

Geophysical Research Letters (ISSN:00948276)

巻号頁・発行日

vol.42, no.10, pp.3998-4006, 2015-05-28

被引用文献数

77

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The global mean sea level (GMSL) was reported to have dropped 5 mm due to the 2010/2011 La Niña and have recovered in 1 year. With longer observations, it is shown that the GMSL went further up to a total amount of 11.6 mm by the end of 2012, excluding the 3.0 mm/yr background trend. A reconciled sea level budget, based on observations by Argo project, altimeter, and gravity satellites, reveals that the true GMSL rise has been masked by El Niño–Southern Oscillation-related fluctuations and its rate has increased since 2010. After extracting the influence of land water storage, it is shown that the GMSL has been rising at a rate of 4.4 ± 0.5 mm/yr for more than 3 years, due to an increase in the rate of both land ice loss and steric change.

著者

Ishii Masao Kosugi Naohiro Sasano Daisuke Saito Shu Midorikawa Takashi Inoue Hisayuki Y.

出版者

American Geophysical Union

雑誌

Journal of Geophysical Research, Oceans (ISSN:01480227)

巻号頁・発行日

vol.116, pp.C06022, 2011-06-28

被引用文献数

56

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Ocean acidification resulting from increases in present and future atmospheric CO2 levels could seriously affect diverse coastal and oceanic ecosystems. In this work, we determine that a significant trend in ocean acidification is superposed on the large seasonal and interannual variabilities of acidity in surface waters off the south coast of Honshu, Japan, based on our repeated observations of partial pressure of CO2 (pCO2), total inorganic carbon (TCO2), and pH. Multiple regression analysis of TCO2 as a function of temperature, salinity, and timing of observations shows that TCO2 increased at a rate of + 1.23 ± 0.40 μmol kg^[-1] yr^[-1] for the period 1994-2008, while no long-term change has been determined for total alkalinity calculated from TCO2 and pCO2 in seawater. These results indicate that pH and the aragonite saturation state (Ωarag) are decreasing at a rate of -0.020 ± 0.007 decade^[-1] and -0.12 ± 0.05 decade^[-1], respectively. If future atmospheric CO2 levels keep increasing as predicted by the Intergovernmental Panel on Climate Change emission scenario A1FI, which postulates intensive fossil fuel use associated with very rapid economic growth, a further reduction of -0.8 to -1.0 in Ωarag is likely in the next 50 years. Such a rapid reduction of Ωarag could have negative impacts on a variety of calcareous organisms.

著者

Nishizawa Seiya Odaka Masatsugu Takahashi Yoshiyuki O. Sugiyama Ko-ichiro Nakajima Kensuke Ishiwatari Masaki Takehiro Shin-ichi Yashiro Hisashi Sato Yousuke Tomita Hirofumi Hayashi Yoshi-Yuki

出版者

American Geophysical Union

雑誌

Geophysical Research Letters (ISSN:00948276)

巻号頁・発行日

vol.43, no.9, pp.4180-4188, 2016-05-16

被引用文献数

19

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火星ダストデビルの性質を解明-火星天気予報や火星有人探査への一歩-. 京都大学プレスリリース. 2016-07-27.

著者

Akiya Y. Saito A. Sakanoi T. Hozumi Y. Yamazaki A. Otsuka Y. Nishioka M. Tsugawa T.

出版者

American Geophysical Union

雑誌

Geophysical Research Letters (ISSN:00948276)

巻号頁・発行日

vol.41, no.19, pp.6943-6948, 2014-10-06

被引用文献数

13

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Spaceborne imagers are able to observe the airglow structures with wide field of views regardless of the tropospheric condition that limits the observational time of the ground-based imagers. Concentric wave structures of the O[2] airglow in 762 nm wavelength were observed over North America on 1 June 2013 from the International Space Station. This was the first observation in which the entire image of the structure was captured from space, and its spatial scale size was determined to be 1200 km radius without assumptions. The apparent horizontal wavelength was 80 km, and the amplitude in the intensity was approximately 20% of the background intensity. The propagation velocity of the structure was derived as 125 ± 62 m/s and atmospheric gravity waves were estimated to be generated for 3.5 ± 1.7 h. Concentric structures observed in this event were interpreted to be generated by super cells that caused a tornado in its early phase.

著者

Kato Hiroaki Onda Yuichi Gomi Takashi

出版者

American Geophysical Union

雑誌

Geophysical research letters (ISSN:00948276)

巻号頁・発行日

vol.39, no.20, pp.L20403, 2012-10

被引用文献数

126

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The Fukushima Daiichi nuclear power plant accident resulted in extensive radioactive contamination of the surrounding forests. In this study, we analyzed fallout 137Cs, 134Cs, and 131I in rainwater, throughfall, and stemflow in coniferous forest plantations immediately after the accident. We show selective fractionation of the deposited radionuclides by the forest canopy and contrasting transfer of radiocesium and 131I from the canopy to the forest floor in association with precipitation. More than 60% of the total deposited radiocesium remained in the canopy after 5 month of the initial fallout, while marked penetration of the initially deposited 131I through the canopy was observed. The half-lives of137Cs absorbed in the cypress and cedar canopies were calculated as 620 days and 890 days, respectively for the period of 0–160 days. The transfer of the deposited radiocesium from the canopy to the forest floor was slow compared with that of the spruce forest affected by fallout from the Chernobyl nuclear reactor accident.

著者

Lengliné O. Enescu B. Peng Z. Shiomi K.

出版者

American Geophysical Union

雑誌

Geophysical research letters (ISSN:00948276)

巻号頁・発行日

vol.39, no.18, pp.L18309, 2012-09

被引用文献数

55

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The 2011, Mw9.0 Tohoku earthquake was followed by an abundant amount of seismicity providing a unique opportunity to analyze the triggering mechanism of great earthquakes. Although the Tohoku earthquake occurred close to a dense seismic network, many aftershocks that occurred in the first few hours after the mainshock are not recorded in the earthquake catalogs. Here we use a template waveform approach to recover as many as possible missing events in the first 12 hours following the Tohoku mainshock. Our analysis is able to detect about 1.4 times more events than those listed in the High Sensitivity Seismograph Network earthquake catalog. Combining our new dataset with earthquakes that occurred at latter times, we are able to observe a continuous decay of the aftershock rate and along strike expansion of aftershock area. We relate the latter observation to the occurrence of post-seismic slip over the deep interface.

著者

Sato Tomonori Tsujimura Maki Yamanaka Tsutomu Iwasaki Hiroyuki Sugimoto Atsuko Sugita Michiaki Kimura Fujio Davaa Gombo Oyunbaatar Dambaravjaa

出版者

American Geophysical Union

雑誌

Journal of geophysical research: Atmospheres (ISSN:2169897X)

巻号頁・発行日

vol.112, no.D17, pp.D17112, 2007-09

被引用文献数

47

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Origin of water vapor, which falls as precipitation over arid/semiarid area in northeast Asia, is investigated by modeling and observational approaches. The regional climate model evaluates the spatiotemporal variations of precipitation and water vapor budget, which are used to drive the single-layer isotope circulation model. Intraseasonal variations of δ 18O in precipitation are well simulated during June-July-August of 2003. The δ 18O in water vapor experiences rapid decreases according to the passage of synoptic-scale disturbances. The rapid decreases of δ 18O are attributed to two processes. (1) The δ 18O in air mass locally decreases over the western mountains associated with the mountain precipitation; the light vapor is advected to eastern Mongolia by the prevailing westerly wind. (2) Convective systems pass by in the vicinity of the observation site, which persistently keep the lower δ 18O in the air mass. Origin of the water vapor during June-July-August in 2003 is evaluated by the colored moisture analysis in which the tracers are assigned depending on the region where the water vapor finally evaporated. Seasonal mean result indicates that the regions contributing to precipitation in Mongolia are not low-latitude regions but central Asia and western Siberia located to the northwest of Mongolia. Observed multilevel isotopic composition supports the model estimation. The moisture transport along the southwesterly wind of the Asian summer monsoon has difficulty reaching Mongolia as a monthly/seasonal mean perspective. However, eastern Mongolia and northeast China are situated on the border area between westerly wind moisture transport (by midlatitude synoptic cyclones) and southerly wind moisture transport (by Asian summer monsoon).

著者

Kawase Hiroaki Yoshikane Takao Hara Masayuki Kimura Fujio Yasunari Tetsuzo Ailikun Borjiginte Ueda Hiroaki Inoue Tomoshige

出版者

American Geophysical Union

雑誌

Journal of geophysical research: Atmospheres (ISSN:2169897X)

巻号頁・発行日

vol.114, pp.D24110, 2009-12

被引用文献数

130 24

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Changes in the Baiu rainband owing to global warming are assessed by the pseudo global warming downscaling method (PGW-DS). The PGW-DS is similar to the conventional dynamical downscaling method using a regional climate model (RCM), but the boundary conditions of the RCM are obtained by adding the difference between the future and present climates simulated by coupled general circulation models (CGCMs) into the 6-hourly reanalysis data in a control period. We conducted the multiple PGW-DS runs using the selected Coupled Model Intercomparison Project Phase 3 (CMIP3) multimodel data set, giving better performance around East Asia in June, and the PGW-DS run using the multiselected CGCM model ensemble mean (PGW-MME run). The PGW-MME and PGW-DS runs show an increase in precipitation over the Baiu rainband and the southward shift of the Baiu rainband. The PGW-MME run has good similarity to the average of all PGW-DS runs. This fact indicates that an average of the multiple PGW-DS runs can be replaced by a single PGW-DS run using the multiselected CGCM ensemble mean, reducing the significant computational expense. In comparison with the GCM projections, the PGW-DS runs reduce the intermodel variability in the Baiu rainband caused by the CGCMs themselves.