The geochemical and geological studies of climate change in the Tertiary age indicate that temperature is controlled by the combined processes of global CO2 cycle (weathering, hydrothermal-igneous activities, metamorphism), ocean circulation, albedo, and development of continental ice-sheet. The temperature change during the Tertiary age has been estimated from analytical data (paleontological data and oxygen isotope data on foraminifera), and computer simulations of the global CO2 cycle. The analytical studies indicate that the middle Miocene age (15-16 Ma) had the climatic optimum. This could be related to the increased rate of CO2 degassing, which was caused by intense hydrothermal-igneous activities at back arc basins, change of mode of plate subduction, and change of ocean circulation pattern. High temperatures in the early Tertiary age (Eocene) are considered to have been also related to CO2 degassing by intense hydrothermal, igneous, and metamorphic activities. The decrease of temperature since the middle Miocene age could have been caused by the combined processes of development of ice sheet, changes in ocean circulation patterns, and intense weathering rate related to the uplifting of the Himalayas.
Iwo Jima is a small volcanic island located in the Western Pacific about 1, 250 km south of Tokyo. The island, with an area about 23 km2, is mostly rimmed by sandy beaches exceeding 200 m in width. No ports or shore protection works have been constructed along the coast of this island since it became a territory of Japan. Further, the beach is always subjected to rough seas because it is fully exposed to the open sea. Therefore, a natural sandy beach has been preserved on this island, where we can observe the coastal geomorphology formed by ocean waves. It should be noted however, that there exists quite an unusual upheaval on this island. Since 1982, the author has been conducting various surveys along the entire coast of Iwo Jima to investigate both crustal movements and variations of the coastal geomorphology of this island. In this paper, cross-levelling data are analyzed to check variations of coastal geomorphology on Iwo Jima. Here, cross-levelling has been done at fifty measuring sections distributed along the entire beach of the island at intervals of roughly 300 m. The surveys have been performed 17 times so far since 1982 at each of the fifty sections, resulting in 850 data points. In the analysis, the following five physical terms have been chosen as the terms representing the features of the coastal geomorphology of the island : (1) Variations of the shoreline in a certain period, Δ Lx ; (2) Foreshore slope, Ifs ; (3) Variations of foreshore area in a certain period, Δ Sfs ; (4) Backshore slope, Ibs ; and (5) Foreshore height, Zfs. Analyses have been done on the data of each physical term to investigate both time-course and local variations. The following is a summary of the findings. (a) Shoreline has advanced roughly 50 m on average over the island during the past 14 years since 1982, and is still advancing at almost the same rate. (b) Foreshore slope is stable at every coast, keeping values which range from roughly 0.15 to 0.22. (c) Foreshore area has been increased roughly 170 m2 on average over the island during the past 14 years since 1982, and is still increasing at almost the same rate. (d) Backshore slope is stable at every coast, keeping values which range from roughly 0.08 to 0.18. (e) Foreshore height ranges from 1.6 m to 4.2 m, although it varies with time and location.
Many Quaternary tephra layers are well preserved in the Kanto and Chubu regions of central Japan. In the last 30 years, radiometric ages for some of these tephra layers were determined by various methods. However, previous fission track ages have been shown to be inaccurate by recent work. In this study, 19 Quaternary tephra layers were newly dated by fission track method with zircon crystals based on zeta calibration, as the I.U.G.S. recommended. The ages determined in the southwest area of the Kanto region, in ascending order of stratigraphy, are as follows : GoP2 : 0.27±0.12 Ma, GoP1 : 0.36±0.16 Ma, HBP : 0.43±0.09 Ma, HcP-1 : 0.64±0.23 Ma, HdP-2 0.40±0.17 Ma, Sa Bi : 0.64±0.06 Ma (error is1σ). Ages determined in the Boso Peninsula are as follows : Ks 5 : 0.39±0.20 Ma, Ku 1 : 0.70±0.25 Ma, Kd 10 : 1.20±0.30 Ma. In the Shinshu area of the Chubu region, eight Quaternary tephra layers were dated as follows : Iz-NY : 0.18±0.08 Ma, A5Pm : 0.31 ± 0.06 Ma, A4Pm : 0.41±0.07 Ma, A3Pm 0.39±0.07 Ma, A2Pm : 0.42±0.08 Ma, A1Pm : 0.47±0.08 Ma, Nashinoki Cl : 0.74 ±0.09 Ma, Misawa Cl : 0.66±0.09 Ma. The ages determined in the Takayama area of Chubu region are as follows Takayama Pumice : 0.43±0.07 Ma, Kamitakara pfl. : 0.55±0.07 Ma.
Detailed morphotectonic and geological research shows the the Quaternary surface deformation processes associated with the thrusting in the eastern Shonai basin, northeast Japan. The Neogene and Quaternary structure in the eastern Shonai basin is dominated by a series of major north-south trending folds and thrust belts which include the Aosawa trend, the Sakata trend, and the Oishi trend from east (mountain-side) to the west (basin central-side). The Aosawa trend, which bounded the Shonai basin and the Dewa Hills, began to move in the late Pliocene. The Sakata trend and the Oishi trend, which are located at the eastern margin of the Shonai alluvial lowland, began to move in the Early Pleistocene and the Middle Pleistocene, respectively with the frontal migration of thrusting. These structures are interpreted to be fault propagation folds on a east dipping detachment fault. On the Aosawa trend, the late Pleistocene terraces are tilted with little faulting overlying the late Pliocene to middle Quaternary reverse faults. On the Sakata trend, the late middle Pleistocene deformation is similar to the underlying Neogene structure, which is characterized by asymmetrical folds with thrusts. On the Oishi trend, the late Quaternary terraces deformed as asymmetrical folding with a narrow flexure zone on the western (thrust tip side) limb overlying symmetrical early to middle Quaternary folds. These morphological figures show the general deformation processes of each structure in the eastern Shonai fold and thrust zone as follows. ·In the early stage, the tip of the concealed thrust elongates to the surface, so the figurefor surface deformation changes from symmetrical folding to asymmetrical folding with a narrow flexure zone on the thrust tip side limb. ·In the middle stage, the fault tip reaches near the surface, with continuing uniformdeformation composed of asymmetrical folding with surface faulting. ·In the later stage, the thrusting on the fault near the surface is decreased, and gentletilting becomes to predominate on the surface. A simple dislocation model suggests that the elongation rate of the fault tip of the thrust underlying the Oishi trend is about 1 mm/yr in the late Pleistocene. This rate is similar to its vertical displacement rate.
Hachijojima, one of the Izu Islands, is located on the Volcanic front of the Izu-Ogasawara (Bonin) Arc which lies south to north along the boundary of the Pacific plate and the Philippine Sea Plate. Hachijojima consists of two stratovolcanoes : Higashiyama and Nishiyama. There is a sharp contrast between Higahshiyama, which is a well-dissected mountain, and Nishiyama, which is cone-shaped. It is topographically clear that Higashiyama was formed earlier than Nishiyama. The following is a summary of the results of this study. 1) The eruptive history of Higashiyama can be divided into six ages : Sokodo I (40-50 ka), Sokodo II (ca. 25-33 ka), Sueyoshi (ca. 17-25 ka), Nakanogo I (ca. 11-17 ka), Nakanogo II (ca. 5.8-11) and Mitsune (ca. 5.8 ka and later). 2) At Higashiyama, a large amount of dacitic magma erupted in the Sokodo I Age and the Sueyoshi Age, and formed a caldera. In the Sokodo I age, the early stratovolcanoes were subjected to landslides and collapsed, and the Higashiyama caldera emarged. In the Sueyoshi Age, the summit of Higashiyama stratovolcanoes were subject to landslides and collapsed to form the Nishihakuunzan caldera. 3) the Higashiyama stratovolcano (young stratovolcano I) was formed in the Sokodo II Age and Mihara stratovolcano (young stratovolcano II a, b) in the Nakanogo I Age by eruptions of basalt and andesite magma. 4) Higashiyama formed a central cone at the end of Nakanogo I Age and eruptions from the summit ended around ca. II ka. Thereafter, it transformed into a flank eruption which issued andesite magma in the Nakanogo II age. In the Mitsune age, volcanic activities of Higashiyama receded. 5) In the Nishiyama region, eruptions became active from the Nakanogo I Age and issued mainly basaltic tephra and pyroclastic surges. However, dacitic tephra was also issued. Occasional finding of pumice fall deposit suggest the generation of daciticmagma. 6) On Higashiyama, deposits Aira-Tn ash (ca. 24.5 ka) and Kikai-Akahoya ash (ca. 6.3 ka) were transported by westerlies from the Kyusyu area. They prove to be important marker tephras clarifing the tephra stratigraphy and eruptive history in this region.
The purpose of this study is to analyze the factors underlying the selection of export channels by exporting firms. The data used in this study were obtained from interviews with 73 firms in Taegu doing export business with Japan. The author analyzed the following three points ; 1) characteristics of export channels selected from an international viewpoint, 2) relations between spatial distribution of customer firms in Japan and selection of export channels by exporting firms, and 3) factors affecting those export channels. The results are summarized as follows; 1. A cluster analysis identified three types of channel selected : direct export (35 firms, 48% of the total), semi-direct export (18 firms, 25%), and indirect export (20 firms, 27%). This result shows the advanced stages of internationalization of the firms studied, according to the Nakano and Kolde models. 2. An analysis of the variance of transactions with customer firms in major cities in Japan by type reveals that Taegu's linkages with Osaka and Tokyo are significantly stronger than those with other cities, reflecting the fact that customer firms are concentrated more in Osaka and Tokyo than in Fukuoka and Nagoya, and that there is no relation between selection of export channels and distribution of customer firms. 3. A factor analysis and a discriminatory analysis revealed five factors underlying the selection of export channels : advantages to growth of exporting firms, concomitant functions with transactions, characteristics of transactions, positive attitudes to export marketing, and international competitiveness of exporting firms
On January 10, 1998, an earthquake with a magnitude of 6.2 occurred in the northwestern Hebei Province, China. The earthquake killed approximately 50 persons and caused widespread damage. The epicenter was at the cross location between two active fault zones, striking E-W and NNE-SSW to NE-SW, located on the north and east edges of the Ordos tableland, respectively. More than 50 strong earthquakes (M≥6) have occurred along the active faults surrounding the Ordos tableland. The native people found some anomalous behavior of animals and luminous phenomenon just before the earthquake. Some peasants reported that, after anomalous light at the early stage of the ground motion, flows of white smoke or vapor came from the fissures. The most damaged area, forming an ellipse with the strike of N-S to NNE-SSW, was centered 8-10 km away from the epicenter, where more than 70-90 % buildings were damaged. Many chimneys and gate pillars of stone fence walls were broken and fell in the SSE-SSW direction at the western side of the inferred surface trace of seismic fault and to the NNE-NNW direction at the eastern side. Aftershocks were concentrated in the most damaged area. Based on the data of the earthquake mechanism, the aftershocks, the damaged area, and the downfallen directions of the chimneys and gate pillars, it is inferred that the surface trace of the seismic fault strikes NNE and dips west.