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Volume 51 (2012)
- Issue 6 Pages 317-
- Issue 5 Pages 297-
- Issue 4 Pages 195-
- Issue 3 Pages 131-
- Issue 2 Pages 65-
- Issue 1 Pages 1-
Volume 51, Issue 3
Displaying 1-4 of 4 articles from this issue
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The Paper for the 2010 Japan Association for Quaternary Research Award
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Atsumasa Okada2012 Volume 51 Issue 3 Pages 131-150
Published: June 01, 2012
Released on J-STAGE: June 12, 2013
JOURNAL FREE ACCESSThe Median Tectonic Line (MTL) fault zone is the longest and most acive intraplate fault in the Japanese Islands. The author has pointed out fault topographies accompanied with right-lateral strike-slip faulting and has made clear the average slip-rate of 5-10mm/y in Shikoku and 1-3mm/y in western Kii Peninsula since 1968. And he has carried out trench excavation surveys, detailed mappings (strip maps and precise active fault maps in the scale of 1 : 25,000 ) along this fault zone and proposed the division to the rupture segments on the MTL. Local governments, the Geological Survey, and university researchers have conducted many kinds of mapping and field surveys (drilling, trenching, seismic refraction survey, etc.) of the active faults to assess their earthquake potentials, especially since the 1995 Kobe earthquake.
Based on the extensive data obtained by these investigations, the characteristics and chronology of Holocene surface faulting on the MTL have illuminated the slip amount of each event in the latest surface rupture and its date. The most recent rupture on the MTL in Shikoku occurred in the 16th century and is probably correlated to the 1596 Keicho earthquake. It is highly probable that the active faults from the Awaji Islands and the south front of the Rokko Mountains to the Arima-Takatsuki fault zone were activated at the same time. As long-term occurrence probabilities for the MTL fault zone were announced to the public by the Earthquake Research Committee of the Headquarters for Earthquake Research Promotion (2003, 2012), the author commented on these evaluations, the problems remaining and perspectives on the future.View full abstractDownload PDF (2816K) -
Ryuji Tada2012 Volume 51 Issue 3 Pages 151-164
Published: June 01, 2012
Released on J-STAGE: June 12, 2013
JOURNAL FREE ACCESSIn 1989, the Ocean Drilling Program (ODP) leg 127 cruise to the Japan Sea recovered a series of Quaternary hemipelagic sediments characterized by millennial-scale rhythmical alternation of dark and light layers, which are traceable basin-wide. Subsequent studies revealed that these dark and light alternations are well correlated with millennial-scale oxygen isotope variations observed in Greenland ice cores, suggesting that they reflect abrupt climatic changes of hemispheric scale. Furthermore, it was demonstrated that deposition of the dark and light alternations was resulted from changes in nutrient flux through the Tsushima Strait, which reflected summer monsoon precipitation over South China. On the other hand, studies on eolian dust component in the Japan Sea sediments demonstrated that dust provenance changed between the Taklimakan Desert and the Gobi Desert in association with the dark and light altenations, suggesting north-south oscillations of the subtropical westerly jet axis. This finding suggests that the westerly jet mediates a tele-connection between East Asian summer monsoon and North Atlantic climate changes on a millennial time scale. The hemipelagic sediments in the Japan Sea preserve a long and continuous record of variation in the East Asian monsoon and its temporal evolution throughout Neogene. Thus the sediments can provide us a unique opportunity to study the onset timing and evolution process of millennial-scale variability of the East Asian monsoon and explore the ultimate cause and amplification and propagation mechanisms of millennial-scale abrupt climatic changes. IODP drilling in the Japan Sea and northern East China Sea is now scheduled in the summer of 2013, and presents a great opportunity for us.View full abstractDownload PDF (1616K)
The Paper for the 2011 Japan Association for Quaternary Research Award
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Yo Naruse2012 Volume 51 Issue 3 Pages 165-174
Published: June 01, 2012
Released on J-STAGE: June 12, 2013
JOURNAL FREE ACCESSThe following six main themes were investigated through my Quaternary studies in the half century since 1949. (1) Geology and depositional environment of the Pliocene to Quaternary formations distributed in the southmost area of the Boso Peninsula. (2) Separation of amount of the Holocene eustatic changes in sea level from that of relative earth movement during the Holocene, examining the height of the elevated shoreline of the marine terraces and the amount of seismic upheaval in 1923. (3) Division of the “Kanto Loam” in the southern Kanto district into four members ; correlation of those members with those of the north Kanto ; tephrochronology of the Kanto Plain ; and its correlation to the glacial chronology in Europe. (4) Stratigraphy of the recent formations and their basal topography in and around Tokyo Bay, and sea level change since the Würmian stage in relation to the development of the lowland plain around Tokyo Bay. (5) Presentation of the Quaternary tectonic map of Japan (1 : 2,000,000) (especially the uplift and subsidence maps), and the distribution maps and catalogue of active faults in and around Japan, (6) Study of the main Pliocene to Quarternary tectonic basins of Japan, especially their rate of subsidence and regional features ; their origin and tectono-deposional development in relation to the subduction of the plates since the Pliocene.View full abstractDownload PDF (1189K)
Article
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Yaeko Igarashi, Toshiro Naruse, Shin’ichi Yatagai, Tohru Danhara2012 Volume 51 Issue 3 Pages 175-191
Published: June 01, 2012
Released on J-STAGE: June 12, 2013
JOURNAL FREE ACCESSVegetation and climate variabilities since MIS 7 were reconstructed using a 13.5m-long sediment core taken from Site 2 in the Kenbuchi Basin, northern Hokkaido, based on pollen analysis, AMS 14C dating, and tephra determination. The reconstructed vegetation in the Kenbuchi Basin was compared with the pollen assemblages of surface mosses collected from the mires of Sakhalin as well as the meteorological data there. During MIS 7, evergreen conifer forest, dominated by Picea in association with Abies and Larix, developed under a cool/moist climate. During the major period of MIS 6, evergreen conifer forest, mainly composed of Picea with more Larix than in MIS 7, and Abies, developed under a cold climate. In the late stage of MIS 6, open Larix forest with Picea, Pinus, and Betula developed under a cold/dry climate, and then Picea forest with Abies and Betula was formed under the ameliorated climate. During MIS 5e, vegetation drastically changed from broad-leaved forests dominated by Quercus to Picea-Abies forests, and then, back again to Quercus dominant forest. Climate in MIS 5e has fluctuated between warm/moist and cool/moist. During MIS 5d dated by Toya tephra (11,200-11,500yrsBP), open Picea-Abies-Betula forest developed under a cool/moist climate. During the latter half of MIS 3, Picea forest with Larix and Pinus has flourished under the stable cool/moist climate. During MIS 2, vegetation changed between the open Larix-Pinus forest associated with Picea and Betula, and open Picea-Pinus-Betula forest, which suggests that the climate has fluctuated between cold/dry and cool/moist conditions. At the beginning of MIS 1, Quercus forest was abruptly formed with Juglans and Ulmus. Then Quercus decreased, and mixed forest of Picea, Abies, Juglans and Ulmus developed under a cool/moist climate. During the major period of MIS 1, the cool temperate broad-leaved forest mainly composed of Quercus has flourished until the present. The rate of climate change from MIS 2 to 1 was more rapid than that from MIS 6 to 5e. Moreover, both interglacial periods were interrupted by remarkable cooling periods.View full abstractDownload PDF (2068K)
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