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Kataoka, Ryuho*; Sato, Tatsuhiko
Geoscience Frontiers, 8(2), p.247 - 252, 2017/03
Times Cited Count：5 Percentile：14.09(Geosciences, Multidisciplinary)Estimation of the depth-dose profile of ionization in protoplanetary disks by galactic cosmic rays (GCRs), solar protons, and by supernova remnants is of great importance in the analysis of planet formation. We therefore calculated the profile using Particle and Heavy Ion Transport code System PHITS. The attenuation length of GCR ionization is updated as 118 g cm
, which is approximately 20% larger than the popular value. Hard and soft possible spectra of solar protons give 5% larger and 20% smaller attenuation lengths compared with those from standard GCR spectra, respectively. Further, all of the attenuation lengths become 10% larger in the compound gas of cosmic abundance, e.g. 128 g cm for GCRs, which can significantly affect the minimum estimate of the size of dead zones in protoplanetary disks.
Sueoka, Shigeru; Tsutsumi, Hiroyuki*; Tagami, Takahiro*
Geoscience Frontiers, 7(2), p.197 - 210, 2016/03
Times Cited Count：18 Percentile：55.9(Geosciences, Multidisciplinary)Thermochronology is a discipline to determine the timing/temperature of past thermal events based on radiometric ages, which is used to reconstruct denudation history of mountains and has been successfully applied to major orogens worldwide. It has been however difficult to apply the method to relatively young/low-relief mountains in Japan. Nonetheless, the recent development of low-temperature thermochronology has greatly expanded its applicability. In this review, we introduce (1) tectonic and geomorphic settings of the Japanese Islands and their mountains, (2) previous attempts to measure uplift/denudation of the mountains in Japan by using methods other than thermochronology, (3) problems of the thermochronologic applications to reveal denudation histories of the Japanese mountains and overview of some previous attempts, and (4) a case study of the Kiso Range and discussions about the current effectivity and applicability of low-temperature thermochronology on the Japanese mountains.
Tokiwa, Tetsuya; Tsusaka, Kimikazu; Matsubara, Makoto*; Ishikawa, Taiki*; Ogawa, Daisuke*
Geoscience Frontiers, 4(1), p.105 - 111, 2013/01
Times Cited Count：8 Percentile：23.68(Geosciences, Multidisciplinary)This paper focuses on the formation mechanism of fractures induced by excavation of a gallery in soft sedimentary rocks in the Horonobe area of Japan. Detailed fracture mapping of the gallery indicates that the fractures consist of both pre-existing fractures (shear fractures) and EDZ fractures (extension fractures). EDZ fractures correspond to bedding planes or potential joints inferred by paleo-stress field, and the EDZ fractures terminate against pre-existing fractures. Therefore, even for excavations in soft sedimentary rocks, formation of the EDZ fractures are controlled by pre-existing fractures and weakness planes associated with bedding planes and potential joints.
