| フルテキストURL | esr_031_cover_j.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2025-03-31 |
| 巻 | 31巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2025 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_031_colophon.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2025-03-31 |
| 巻 | 31巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2025 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| JaLCDOI | 10.18926/ESR/68676 |
|---|---|
| タイトル（別表記） | Improved sedimentary layer model including the accretionary prism in the fore-arc region of the Ryukyu arc, Japan |
| フルテキストURL | esr_031_001_015.pdf |
| 著者 | 小松 正直| 浦上 想平| 岡元 太郎| 竹中 博士| |
| 抄録 | We combine the recent seismic reflection profiles to construct a new seismic velocity model of the sedimentary layer incorporating the accretionary prism along the Ryukyu trench. In constructing the new model, we refer to the zoning (ZONE1 to ZONE4) identified by Okamura et al. (2017, Tectonophys.). The construction process consists of the following steps: First, we digitize either unconformities or VP=4 to 5 km/s lines as the seismic basement, whichever is more clearly identifiable. Second, the digitized thickness data of the sedimentary layer from the reflection profiles are geometrically modeled and interpolated to make the three-dimensional structure model. Finally, we supplement the external region of the constructed 3-D sedimentary model using the J-SHIS model provided by the NIED to complete the velocity structure model in the entire Ryukyu arc. The main features of our model are as follows: In ZONE1, off Ishigaki-jima island, the thick sedimentary layer extends about 50 km wide from the Ryukyu trench. In ZONE2, off Miyako-jima island, the thinner layer compared to the other zones is found near the trench, with a thin sedimentary terrace covering the area behind it. In ZONE3, off Okinawa-jima island, the sedimentary layer deepens as it approaches the trench. In ZONE4, off Tokara islands, the deepest layer among all zones is identified. We then conduct 3-D finite-difference simulations of seismic wave propagation using the new and the previous models to confirm the improvement of the new model. In the simulations, the effects of the accretionary prism along the Ryukyu trench on the seismic wave propagation are clearly identified. |
| キーワード | Sedimentary layer model Accretionary prism Ryukyu arc |
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2025-03-31 |
| 巻 | 31巻 |
| 号 | 1号 |
| 開始ページ | 1 |
| 終了ページ | 15 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2025 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_031_titlepage.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2025-03-31 |
| 巻 | 31巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 英語 |
| 著作権者 | © 2025 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_031_cover.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2025-03-31 |
| 巻 | 31巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 英語 |
| 著作権者 | © 2025 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_030_cover_j.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2024-03-31 |
| 巻 | 30巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2024 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_030_colophon.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2024-03-31 |
| 巻 | 30巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2024 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| JaLCDOI | 10.18926/ESR/66846 |
|---|---|
| フルテキストURL | esr_030_021_035.pdf |
| 著者 | MAURER, Robert| HARKER, Stuart| SUZUKI, Shigeyuki| WHEELER, Allan| |
| 抄録 | Mantle convection currents are the currently accepted driving force for plate tectonics that have ripped apart the continents and created oceans. Because of these actions, continental collisions and ocean closures have resulted. Our paper challenges the conventional concept and provides an alternate, mathematically justified drive mechanism. The pull-push motions of such convection currents in the upper mantle are here concluded to be too weak to be the driving mechanism. Our proposal for such global scale forces concerns the effect of an offset centre of mass of the Earth that results in rotational wobbling. Kepler’s laws of planetary motion demonstrate the rotational behavior of the Earth to be aligned with the Sun on the outward and inward motions of the elliptical orbit. The unbalanced rotation on a fixed gravitational axis results in circumferential stresses on the outer Earth’s rim that is more than strong enough to pull the continental plates apart. The proposed unbalanced rotational stress force equation is shown to be sufficient to drive the cyclic breakup and reassembly of the continental plates, as well as the generation of new oceanic crust and subduction zones. Mantle convection currents are here demonstrated to have a passive rather than active role in the plate movements. |
| キーワード | Differential circumferential tensile force Rotating Earth Offset centre of mass radius of eccentricity |
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2024-03-31 |
| 巻 | 30巻 |
| 号 | 1号 |
| 開始ページ | 21 |
| 終了ページ | 35 |
| ISSN | 1340-7414 |
| 言語 | 英語 |
| 著作権者 | © 2024 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| JaLCDOI | 10.18926/ESR/66845 |
|---|---|
| タイトル（別表記） | Microtremor exploration in Tsushima Campus, Okayama University |
| フルテキストURL | esr_030_013_020.pdf |
| 著者 | 山田 伸之| 竹中 博士| |
| 抄録 | In this report, microtremor array observations were conducted in the Tsushima Campus of Okayama University, and the subsurface velocity structure was estimated from the analysis of the records. The results indicate that a five-layer S-wave velocity structure from the surface to the seismic basement equivalent layer with thicknesses of 8, 24, 80 and 180 m and velocities of 150, 450, 1100, 1700 and 3200 m/s, respectively, is reasonable. This model explains to some extent the observed phase velocity and H/V spectral ratios. It is also consistent with the surface borehole results. Furthermore, the areal characteristics of the H/V spectral ratios were also presented, allowing us to estimate the trend of the ground structure in shallow areas. |
| キーワード | Okayama Microtremor array exploration S-wave velocity H/V spectral ratio |
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2024-03-31 |
| 巻 | 30巻 |
| 号 | 1号 |
| 開始ページ | 13 |
| 終了ページ | 20 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2024 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| JaLCDOI | 10.18926/ESR/66844 |
|---|---|
| タイトル（別表記） | Petrological characteristics of the stone chamber of Tobiotsuka Kofun, Okayama Prefecture |
| フルテキストURL | esr_030_001_012.pdf |
| 著者 | 金子 峻大| 野坂 俊夫| 清家 章| |
| 抄録 | Tobiotsuka Kofun, a tumulus built on the Misu Hills in the Kofun period, has a horizontal stone chamber made of huge stone blocks with a width up to 2 meters or more. To specify the source of the stone blocks, we carried out the measurement of magnetic susceptibility, petrographic observation, and chemical analysis of minerals. The stones are amphibole-biotite granite with phenocrystic large grains of K-feldspar. The back-wall stone of the chamber has higher magnetic susceptibility than ceiling and side-wall stones, which probably results from a higher amount of magnetite formed by the alteration of biotite in the back-wall stone. Furthermore, the back-wall stone is different from ceiling stone in that it has lower XMg [Mg/(Mg + Fe) mole ratio], lower Al, Ti, and Na + K contents and higher Si contents of amphibole, higher XMg of biotite, and shows a tendency to have higher Na (albite component) contents at rims of plagioclase crystals and lower Ti contents of zircon. These characteristics of the back-wall stone are similar to those of granite exposed in the Koshinzan area about 2 km northeast of Tobiotsuka Kofun, whereas the ceiling and side-wall stones are similar to granite outcrops in the vicinity of Tobiotsuka Kofun, e.g., in the Midoriyama area. It is concluded that the quarry for the back-wall was located at a different place from that for the ceiling and side-wall stones. |
| キーワード | Tobiotsuka Kofun stone chamber granite |
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2024-03-31 |
| 巻 | 30巻 |
| 号 | 1号 |
| 開始ページ | 1 |
| 終了ページ | 12 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2024 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_030_titlepage.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2024-03-31 |
| 巻 | 30巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 英語 |
| 著作権者 | © 2024 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_030_cover.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2024-03-31 |
| 巻 | 30巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 英語 |
| 著作権者 | © 2024 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_029_cover_j.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2023-03-31 |
| 巻 | 29巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2023 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_029_colophon.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2023-03-31 |
| 巻 | 29巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2023 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| タイトル（別表記） | ERRATA: FDM simulation of long-period ground motions around Oita Prefecture, Japan, using a land-ocean unified 3D structure model |
|---|---|
| フルテキストURL | esr_029_065_066.pdf |
| 著者 | 奥仲 達也| 小松 正直| 竹中 博士| 吉見 雅行| 中村 武史| 岡元 太郎| |
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2023-03-31 |
| 巻 | 29巻 |
| 号 | 1号 |
| 開始ページ | 65 |
| 終了ページ | 66 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2023 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| JaLCDOI | 10.18926/ESR/65481 |
|---|---|
| タイトル（別表記） | Onset time and location of the main rupture of the 2018 Hokkaido Eastern Iburi, Japan, earthquake |
| フルテキストURL | esr_029_049_063.pdf |
| 著者 | 小割 啓史| 小松 正直| 竹中 博士| |
| 抄録 | The rupture process at the beginning stage of the 2018 Hokkaido Eastern Iburi, Japan, earthquake (MJ 6.7) is investigated by analyzing P-wave records from local strong-motion stations. The records show about 3 s of small amplitude arrival (so-called "initial rupture phase") followed by the onset of the main energy release ("main rupture phase"). In this paper we address the issue: where the seismic energy release corresponding to the main rupture phase started at the primary stage of the main rupture, by locating the main rupture onset position. For this aim we applied the 2D and the 3D search methods to estimate the relative location of the onset of the main rupture with respect to the hypocenter, and the time difference between them. The 2D method assumes a plausible initial fault plane and locates the main rupture onset position on the initial fault plane, while the 3D method does not require such assumed fault planes. In the 2D method we employed each of the nodal planes of the first-motion focal mechanism as the initial rupture plane. The 3D method was able to give a better solution than the 2D one. It suggests that the main rupture initiation point might not be on the same fault plane as the hypocenter is. The solution shows that the main rupture onset point is 5.8 km southward and 2.5 km upward from the hypocenter, with the rupture time of 3.3 s from the origin time. It is consistent with the previous studies on the relationship between the magnitude and the initial rupture duration. |
| キーワード | 2018 Hokkaido Eastern Iburi earthquake fault plane initial rupture strong motion |
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2023-03-31 |
| 巻 | 29巻 |
| 号 | 1号 |
| 開始ページ | 49 |
| 終了ページ | 63 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2023 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| JaLCDOI | 10.18926/ESR/65480 |
|---|---|
| タイトル（別表記） | Summary of our activities toward development of the ESD interdisciplinary study plans on climate and cultural understanding education with attention to the seasonal cycle and “seasonal feeling” around Japan and Europe |
| フルテキストURL | esr_029_029_048_rev.pdf |
| 著者 | 加藤 内藏進| 加藤 晴子| 赤木 里香子| |
| 抄録 | We have continued the interdisciplinary integration of the knowledge on climate and music and have developed the crosscutting study plans on the climate and cultural understanding education. A part of these results had been summarized in a Japanese book titled “Climate and music (Cultural understanding and ESD spreading from the “Doors of Song”)” (Kato and Kato 2019), building mainly our papers written in Japanese. This article will re-integrate our above study results, mainly for the climate and songs/traditional seasonal events around Germany, Northern Europe and Japan, with special attention to (A) asymmetric seasonal progression from autumn to next spring around Japan, (B) winter climate around Germany in association with the seasonal feeling on the traditional events “Fasnacht” for driving winter away and (C) climate around Northern Europe in association with the seasonal feeling on the summer solstice festival “Juhannus” with comparison to the summer climate around Japan. |
| キーワード | climate and music interdisciplinary climate and cultural understanding education seasonal cycle around Japan and Europe seasonal feeling ESD comparative climatology |
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2023-03-31 |
| 巻 | 29巻 |
| 号 | 1号 |
| 開始ページ | 29 |
| 終了ページ | 48 |
| ISSN | 1340-7414 |
| 言語 | 英語 |
| 著作権者 | © 2023 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| JaLCDOI | 10.18926/ESR/65479 |
|---|---|
| タイトル（別表記） | Geology of the Paleogene to Neogene successions and gentle upwarping of the Kibi Plateau Surface, surrounding area of Kibichuou Town, Okayama Prefecture, Southwest Japan |
| フルテキストURL | esr_029_001_027.pdf |
| 著者 | 田中 元| 鈴木 茂之| |
| 抄録 | The Paleogene to Neogene successions which are composed of the Paleogene Kayo Formation, the late Oligocene to earliest Miocene Yagane Formation and the middle Miocene Ukan Formation are sporadically distributed in the Kibi Plateau region, surrounding area of Kibichuou Town, Okayama Prefecture, Southwest Japan. The gravel of the Kayo Formation occupied paleo-valley of Pre-Paleogene basement. The Yagane and Ukan formations unconformably overlay Pre-Paleogene rocks and occupy the gentle valley on the Kibi Surface as valley fill deposits. The fluvial of the Kayo Formation is mainly composed of conglomerate with minor amount of sandstone and mudstone. The fluvial Yagane Formation is mainly composed of conglomerate and associated with sandstone, mudstone and coal beds. The marine Ukan Formation is subdivided into 3 members, the Yamagata Muddy sandstone Member (YMM), the Shimoyokomi Sandstone Member (SSM) and the Tsuneyama Mudstone Member (TMM) in ascending order. The YMM is characterized by the bio-disturbed very poorly sorted muddy sandstone with frequent burrows, which indicate tidal flat deposits. The SSM is mainly composed of parallel bedded well-sorted sandstone with occasional burrows, which suggest near shore deposits. The TMM is composed of homogeneous clay rich mudstone, which implies off shore deposits. The boundary between the SSM and TMM (the contact of the sandstone and mudstone) is distinctive and correlative throughout the study area. The boundary is considered to be formed under similar water depth. The variations of the boundary height indicate a later ground movement. From the north to the south in about 25km distance, the height of the boundary changes 260m (in Ukan), 300m (in Takeshou), 360m (in Kibikogentoshi) and 260m (in Nichiouji). It indicates that a very gentle upwarping of the Kibi Plateau Surface was formed after the deposition of the Miocene. |
| キーワード | Kibi Plateau Surface Upwarping Miocene Ukan Formation |
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2023-03-31 |
| 巻 | 29巻 |
| 号 | 1号 |
| 開始ページ | 1 |
| 終了ページ | 27 |
| ISSN | 1340-7414 |
| 言語 | 日本語 |
| 著作権者 | © 2023 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_029_titlepage.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2023-03-31 |
| 巻 | 29巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 英語 |
| 著作権者 | © 2023 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |
| フルテキストURL | esr_029_cover.pdf |
|---|---|
| 出版物タイトル | Okayama University Earth Science Report |
| 発行日 | 2023-03-31 |
| 巻 | 29巻 |
| 号 | 1号 |
| ISSN | 1340-7414 |
| 言語 | 英語 |
| 著作権者 | © 2023 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved |
| 論文のバージョン | publisher |