Negative excursion of surface electric fields during gamma-ray glows in winter thunderstorms

Wada, Yuki*; Kamogawa, Masashi*; Kubo, Mamoru*; Enoto, Teruaki*; Hayashi, Shugo*; Sawano, Tatsuya*; Yonetoku, Daisuke*; Tsuchiya, Harufumi

Journal of Geophysical Research; Atmospheres, 128(21), p.e2023JD039354_1 - e2023JD039354_20, 2023/11

https://doi.org/10.1029/2023JD039354

Termination of downward-oriented gamma-ray glow by normal-polarity in-cloud discharge activity

Wada, Yuki*; Wu, T.*; Wang, D.*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Morimoto, Takeshi*; Nakamura, Yoshitaka*; Shinoda, Taro*; Tsuchiya, Harufumi

Journal of Geophysical Research; Atmospheres, 128(15), p.e2023JD038606_1 - e2023JD038606_9, 2023/08

https://doi.org/10.1029/2023JD038606

Denudation process of crystalline nappes in a continental collision zone constrained by inversion of fission-track data and thermokinematic forward modeling; An Example from Eastern Nepalese Himalaya

Nakajima, Toru; Kawakami, Tetsuo*; Iwano, Hideki*; Danhara, Toru*; Sakai, Harutaka*

Journal of Geophysical Research; Solid Earth, 127(5), p.e2021JB023630_1  - e2021JB023630_33, 2022/05

https://doi.org/10.1029/2021JB023630

The thermochronological methods were applied to the Higher Himalayan Crystalline (HHC) nappe and the underlying Lesser Himalayan sediments (LHS) to elucidate the denudation process of the middle- and upper-crust of eastern Nepal over the geological time scale. The thermochronological inverse analysis was undertaken for new results of fission-track (FT) age and FT length data of zircon and apatite in order to reconstruct the time-temperature () paths in the temperature range of 60-350 degree. Eight paths obtained along the across-strike section showed that the cooling process of the HHC nappe was characterized by following three aspects: (1) gradual cooling followed by rapid cooling and subsequent gradual cooling, (2) northward-younging of the timing of the rapid cooling, (3) gradual cooling followed by ca. 2 Myr rapid cooling in the frontmost part of the HHC nappe. The observed FT ages and paths were then compared with those predicted by forward thermokinematic modeling. The results of the thermokinematic modeling for the Flat-Ramp-Flat MHT model, in which the HHC and the underlying LHS are denudated accompanied with the movement of the Main Himalayan Thrust (MHT), well reproduced the observed paths and FT ages in eastern Nepal. This suggests that the observed FT ages and paths reflect a denudation process driven by the movement of the MHT showing the flat-ramp-flat geometry, and that the denudation rate and its spatial distribution have roughly been constant in eastern Nepal since ca. 9 Ma.

Deposition and dispersion of radio-cesium released due to the Fukushima Nuclear accident, 2; Sensitivity to aerosol microphysical properties of Cs-bearing microparticles (CsMPs)

Kajino, Mizuo*; Adachi, Koji*; Igarashi, Yasuhito*; Satou, Yukihiko; Sawada, Morihiro*; Sekiyama, Tsuyoshi*; Zaizen, Yuji*; Saya, Akane*; Tsuruta, Haruo*; Moriguchi, Yuichi*

Journal of Geophysical Research; Atmospheres, 126(1), p.e2020JD033460_1 - e2020JD033460_23, 2021/01

https://doi.org/10.1029/2020JD033460

Photonuclear reactions in lightning, 2; Comparison between observation and simulation model

Wada, Yuki*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; Furuta, Yoshihiro; Odaka, Hirokazu*; Makishima, Kazuo*; Tsuchiya, Harufumi

Journal of Geophysical Research; Atmospheres, 125(20), p.e2020JD033194_1 - e2020JD033194_15, 2020/10

https://doi.org/10.1029/2020JD033194

Inverse magnetic susceptibility fabrics in pelagic sediment; Implications for magnetofossil abundance and alignment

Usui, Yoichi*; Yamazaki, Toshitsugu*; Oka, Toshitaka; Kumagai Yuho*

Journal of Geophysical Research; Solid Earth, 124(11), p.10672 - 10686, 2019/11

https://doi.org/10.1029/2019JB018128

We report the discovery of inverse AMS fabrics from pelagic clay recovered by a 12 m long piston core from the western North Pacific. Rock magnetic data and ferromagnetic resonance spectroscopy indicated that magnetofossils account for most of the mean susceptibility regardless of normal or inverse AMS, suggesting that the inverse AMS fabrics due to magnetofossils may be widespread in pelagic clay.

Analysis of the ozone reduction event over the southern tip of South America in November 2009

Akiyoshi, Hideharu*; Kadowaki, Masanao; Nakamura, Haruna*; Sugita, Takafumi*; Hirooka, Toshihiko*; Harada, Yayoi*; Mizuno, Akira*

Journal of Geophysical Research; Atmospheres, 123(22), p.12523 - 12542, 2018/11

AA2018-0443.pdf:12.61MB

https://doi.org/10.1029/2017JD028096

A reduction of the total ozone over the southern tip of South America lasting 3 weeks occurred in November 2009. Analyses of the ERA-Interim reanalysis data and the total ozone observed by the Ozone Monitoring Instrument indicate that the total ozone reduction event was caused by a migration of the polar vortex toward the South American continent at the time of the vortex breakup. The vortex migration is associated with an enhanced wave flux from the troposphere at 120-150W and 50-60S to the west of the South American continent to the stratosphere over the southern part of the continent, which led to a large negative geopotential height anomaly in the lower stratosphere. In November, a blocking event was diagnosed from the 500-hPa geopotential height over the west of the South American continent. These results suggest a relation between the long-lasting reduction of the total ozone over the southern tip of South America and the blocking phenomenon in the troposphere of the Southern Hemisphere through wave propagation from the blocking region in 2009. Analysis of the total ozone anomaly for 50-60S and 65-75W over the southern tip of South America in November for 1979-2015 indicates that the negative ozone anomaly in November 2009 was one of the largest anomalies in this 37-year period and was associated with the large negative geopotential height anomaly in the lower stratosphere. Analyses of dynamical fields were also conducted for other years with large geopotential height anomalies.

Atmospheric modeling of Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of Japan

Kitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.

Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07

https://doi.org/10.1029/2017JD028230

We compared seven atmospheric transport model results for Cs released during the Fukushima Daiichi Nuclear Power Plant accident. All the results had been submitted for a model intercomparison project of the Science Council of Japan in 2014. We assessed model performance by comparing model results with observed hourly atmospheric concentrations of Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.

Uplift and denudation history of the Akaishi Range, a thrust block formed by arc-arc collision in central Japan; Insights from low-temperature thermochronometry and thermokinematic modeling

Sueoka, Shigeru; Ikeda, Yasutaka*; Kano, Kenichi*; Tsutsumi, Hiroyuki*; Tagami, Takahiro*; Kohn, B. P.*; Hasebe, Noriko*; Tamura, Akihiro*; Arai, Shoji*; Shibata, Kenji*

Journal of Geophysical Research; Solid Earth, 122(8), p.6787 - 6810, 2017/08

http://doi.org/10.1002/2017JB014320

no abstracts in English

Far-field stress dependency of the failure mode of damage-zone fractures in fault zones; Results from laboratory tests and field observations of siliceous mudstone

Ishii, Eiichi

Journal of Geophysical Research; Solid Earth, 121(1), p.70 - 91, 2016/01

https://doi.org/10.1002/2015JB012238

Macroscopic failure modes (extensional failure or shear failure) in fault damage zones influence hydrogeological properties of fault zones. Based on the Griffith-Coulomb criterion and a simple assumption that the failures are predominantly induced by increasing of differential stresses and/or decreasing of effective normal stresses due to stress concentration along faults, it is implied that extension fractures can exclusively propagate from the faults when the effective mean stress is less than twice the rock tensile strength, whereas shear fractures also can develop when the effective mean stress is more than twice the rock tensile strength, which suppresses the formation of extension fractures. In this study, mechanical tests (the undrained triaxial tests and the unconfined compressive strength tests) using siliceous mudstone specimens given artificial fault(s) were performed under multiple effective confining pressures. Comparison between the damage zone fractures formed at the fault tips by the tests and the loaded effective mean stresses provided results consistent with the above simple model. The similar results are also suggested from the occurrence of natural damage zone fractures observed in the same siliceous mudstone by core logging. Laboratory-measured tensile strengths could be used as the lower threshold strengths considering the strain rate and scale effects and it is implied that hard-linked highly permeable fault zones involving many extension fractures are limited to rock domains which have experienced the effective mean stress less than twice the tensile strength.