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

57

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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

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

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

14

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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

127

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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.