著者
青山 雅史
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.111, no.4, pp.583-593, 2002-08-25
参考文献数
25
被引用文献数
4 1

Mean annual air temperature (MAAT), mean annual surface temperature (MAST), bottom temperature of winter snow cover (BTS), and morphometric parameters of rock glaciers indicate the states of the rock glacier activities in the Yari-Hotaka mountain range, Northern Japanese Alps. The air temperature conditions at the Mountain Hut Minamidake suggest that this monitoring site belongs to the discontinuous permafrost zone. The BTS and MAST values at the North and South Okiretto rock glaciers indicate the occurrence of permafrost. BTS and MAST at the Tenguppara I rock glacier indicate the absence of permafrost. At the North Minamisawa rock glacier, MAST was slightly above 0 °C, accordingly degrading permafrost that possibly exists in this rock glacier. These rock glaciers are not moving at present, as inferred from the morphologic and vegetational characteristics of these rock glaciers. These results suggest that the North Minamisawa, North Okiretto, and South Okiretto rock glaciers are of the inactive type, and Tenguppara I rock glacier is of the fossil type. The other rock glaciers in this mountain range are of the fossil type, as inferred from collapse and subdued forms, and extensive vegetation cover.
著者
古村 孝志 武村 俊介 早川 俊彦
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.116, no.3, pp.576-587, 2007-08-25
参考文献数
15
被引用文献数
5 9

Large and prolonged shaking with long-period ground motions having periods of about 7 sec were observed in central Tokyo during the Off Niigata-ken Chuetsu, Japan, M6.8 earthquake on 16 July, 2007. The observed ground motions from a dense nationwide strong motion network (KNET and KiK-net) demonstrate clearly that the long-period ground motions consist of Rayleigh waves, which developed at the northern edge of the Kanto Basin and were induced by conversion from the S waves radiating from the earthquake source. The amplitude and the duration of the long-period surface waves were enhanced dramatically as they propagated in the Kanto Basin, which has a thick cover of sedimentary rocks overlaying rigid bedrock. Observed ground motions of long-period signals at the center of Tokyo from the 2007 Off Niigata-ken Chuetsu event correlated well with observations from the Chuetsu earthquake on 23 Oct. 2004 (<I>M</I> 6.8). By analyzing waveform data from the main shock and aftershocks of the 2007 Off Niigata-ken Chuetsu earthquake and the Chuetsu earthquake in 2004, it is found that the long-period surface wave having a dominant period of about 7 sec at the center of Tokyo is developed efficiently by a large earthquake with a magnitude greater than about M6.5-7, but it is not developed by small earthquakes of less than about <I>M</I>6.5.
著者
久田 英子
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.110, no.1, pp.1-16, 2001
被引用文献数
1

The Vredefort Dome, located in the central part of the Witwatersrand Basin in South Africa, is the type locality for pseudotachylite. Pseudotachylite at the Vredefort Dome is generally regarded to be of impact origin. Pseudotachylites which are closely associated with faults are, however, also known to be common along the northern and northwestern edges of the Witwatersrand Basin. In order to compare pseudotachylites from the Vredefort Dome and from the surrounding Witwatersrand Basin, different studies were undertaken in the past. Mode of occurrence, microscopic textures, geochemical analyses and chronological measurements of pseudotachylites are briefly reviewed in this paper.<BR>In the Vredefrot Dome, pseudotachylites are commonly observed except in the central part of its core. In the surrounding Witwatersrand Basin, they are reported from drill core sections and in underground workings. The matrix in pseudotachylite from the Vredefort Dome is mostly a recrystallized melt phase, while those from the surrounding Witwatersrand Basin seem to be composed of clastic material. Pseudotachylites both from the Vredefort Dome and the surrounding Witwatersrand Basin are geochemically closely related to their host rocks. Although evidence for more than one generation of pseudotachylite has been presented, both in the Vredefort Dome and the surrounding Witwatersrand Basin, it is widely believed that most of them were formed as a result of the Vredefort impact event (<I>ca</I>. 2.0 Ga). Other fault rocks reported from the surrounding Witwatersrand Basin are older than the pseudotachylites and therefore not related to their formation.
著者
吉田 明夫 高山 博之
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.103, no.6, pp.696-705, 1994-12-10
参考文献数
12
被引用文献数
1 1

We show that seismic activity decreased clearly in a wide area before the 1953 Boso-oki earthquake and the 1972 Hechijojima-toho-oki earthquake. In both cases the seismic quiescence extended to the Tokyo Metropolitan area. Marking precursory activity appeared several years before the Boso-oki earthquake in the Chiba prefecture and in the sea region off-Ibaraki prefecture. It is also noted that the seismicity in the Kanto region as well as in the sea region south off-Boso Peninsula decreased conspicuously after the Boso-oki earthquake. On the contrary an increase of the seismicity was observed after the Hachijojima-toho-oki earthquake, although deep seismic activities decreased remarkably. We show that seismic quiescences preceding the Boso-oki earthquake and the Hachijojima-toho-oki earthquake were detectable before their occurrences, and no other statistically significant quiescence has appeared in the south off-Kanto region since 1926. It is proposed that the occurrence of a large earthquake may be predicted by monitoring changes of the seismicity in a wide area.
著者
町田 洋 新井 房夫 村田 明美 袴田 和夫
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.83, no.5, pp.302-338, 1974
被引用文献数
25 17

This paper presents the basic data for tephrochronology of the Middle Pleistocene events of South Kanto, Central Japan. The tephra preceding to the last interglacial age (the Tama tephra) is found in highly dissected terraces (Fig. 1) much thicker than the younger tephra formations (Fig. 2). It is subdivided into five formations from T-A to T-E in order of increasing age (Table 1 and Fig. 2). This classification is based not on the eruptive history of the volcanoes but on the sequence of terraces. The relationship between these two is shown in Fig. 2.<BR>Of the four columnar sections (Fig. 6), section 1, synthesized from many sections in the Ooiso Hill (Fig. 3), 25 km east of the Hakone volcano, provides a standard section for South Kanto. There are so many tephra layers of the Tama stage (about 150 m in thickness) preserved in a relatively fresh state, that they are expected to cover a long time in the Middle Pleistocene. A detailed description is therefore needed for specifying any particular tephra bed. 75 marker beds have been selected, and described in terms of lithological and petrographical characteristics as in Table 2 and Fig. 4. The most valuable for characterizing marker tephras are the refractive indices of orthopyroxene and hornblende.<BR>The distribution and the petrographic character of tephras indicate that the tephras mainly comprising two pyroxene phenocrysts might come chiefly from the Old Somma of the Hakone volcano (Fig. 8-1 and 8-2) and partly from the Ashitaka volcano. Whereas such salic tephras with abundant hornblende, biotite and other phenocrysts as GoPi and TE-5 might originate from distant volcanoes (Fig. 8-3).<BR>As a result of precise examination, tens of the marker beds have been traced eastward to the environs of Tokyo and Yokohama (Fig. 6), where the standard Quaternary sequence had been established. Furthermore, several marker beds have been recognized within the Middle Pleistocene marine sediments in the Boso Peninsula. By use of these the Quaternary stratigraphy already established in South Kanto is significantly revised (Table 3 and 6).
著者
渡辺 和衞
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.64, no.3, pp.71-86, 1955

1) All geological phenomena in research works reveal its substance according to the sharp conceptions concerning its stratigraphical position and structural aspect. Especially, younger sediments, Neogene Tertiary, have more intricated forming process and interbed highly evoluted flora & fauna, therefore its stratigraphical subdivision meets accelerated difficulties along with the advance of geologic times. On this account, the geochemical criteria, i. e. -pleochroic halos or radioactivity, and the keybed probation have considerably been available to explain the geologic system. Above all the age determination method of C<SUP>14</SUP> ratio is the epoch-making discovery, in this century, but its applicable scope is about 30, 000 years. And its accuracy has often given rise to discussion from the stratigraphical view point. Recently Ernst Antevs discusses this problem in the report. (Jour. of Geology, Vol. 61, No. 3, 1953, p. 195-230) Another excellent works were published by W. D. Urry in 1949 by the tool of the &ldquo;percentage of equilibrium method&rdquo; for uranium, ionium, and radium. (ibid.p.252-262) But this method has its applicable scope of 300, 000 years. Setting aside this scope problem, these contributions have surely been valid to make the rigid progress of the earth science.<BR>2) The author has recently established the age determination method, that is, as stated above, &ldquo;the percentage equilibrium method&rdquo; for organic carbon. (K. Watanabe : The chronological significance of coal, Bull. Geol. Surv. Japan., Vol. 2, No. 8, 1951) In 1953, this device was reasonably appreciated by Dr. D. W. Van Krevelen, Director of the Central Research Laboratory in Holland. Thereafter this method has greatly been improved by making a comparative study with C14 method (three Japanese specimens, No. 629, 548, 603, determined by Libby were used.). These are considerably satisfactory results to the effect that they are not absolute but relative, Needless to say, this organic carbon method has a chronological index -&theta; (0&deg;-180&deg;), ranging from the present time to Carboniferous period or so on. Accordingly he applied this method to 76 specimens from Kuwana district. (Table 2, Fig. 3). These specimens have various indices ranging from 0.2&deg; to 5.9&deg; (3, 000 years-12, 600, 000 years; recent?upper Miocene). Synthesizing these data, he has drawn the new map, -Isogeochronological map of Kuwana. (Fig. 4) Of course these indices have performed a r&ocirc;le of the correlative tool and manifested several new geologic phenomena which had not been found before. He can show them as follows ;<BR>(1) Synchronous bed with the Chigusa member (marine sediments) exclusively depositing on the side of the Suzuka mountains has been detected on the other side of the Yoro mountains as a member of the terrigenous deposits.<BR>(2) The tentative boundary between Tertiary and Quaternary has quantitatively been determined.<BR>(3) A presumptive fault or folding A-B has been found out by recognizing the uncontinuous zone of &theta;-Isohypsen.<BR>(4) Both structural basins (Machiya system and Asaka system) have contracted drainage areas downwards by upwarping movement at the coastal plain.<BR>(5) Collectively all geologic displacements and fluctuations can quantitatively be measured.<BR>3) Applied geology of this region.<BR>(1) Porcelain clay or other lower class clay.<BR>By organic carbon method of age determination, synchronous strata with ones interbedding good porcelain clay (kaolinite-rich) at Seto, Tajimi, have been detected in this region, -Minami-Nakatsuhara, Tado, Oharaisshiki etc, but its quality is not so good as those porcelain clay. On the contrary, the Chigusa marine bed is rich in montmorillonite or illite minerals. All other lower class clay can be traced their origins and occurrences by Fig. 4 chart from the environmental or genetic point of view. (cf. Fig. 5)
著者
鶴岡 弘 大竹 政和
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.111, no.2, pp.256-267, 2002
参考文献数
34
被引用文献数
1 6

We conducted a numerical simulation to clarify the effects of the earth tide on earthquake occurrence. In the simulation, fault planes, having different initial stresses, are loaded by constantly increasing tectonic stress and cyclic stress due to the earth tide. Earthquakes are assumed to occur when the shear stress reached a certain threshold level. The result of the simulation indicates that the tidal effect on earthquake occurrence is strongly controlled by the ratio of stress change rate between earth tide and tectonic stress accumulation; earthquakes concentrate near phase angle 0&deg; (maximum tidal stress) when the ratio is large, and they are distributed with a peak around-90&deg; (maximum acceleration of tidal stress) when the ratio is small. This phase selectivity is very similar to the observations of tidetriggered earthquakes reported so far, and rock failure experiments under cyclic loading, suggesting that our approach may provide an important clue for clarifying the physical mechanism of tidal triggerings of earthquakes. Schuster's test has been widely used for detecting tidal effect on earthquake occurrence. However, it is shown by the numerical simulation that the result of a test strongly depends on the size of a data set when earthquakes have phase selectivity by nature, and that Schuster's <I>p</I>-value is not appropriate to represent the strength of tidal effects. Alternatively, we propose to use &alpha;, which is the amplitude of a sine curve fitted to the frequency distribution of earthquakes against phase angle, to evaluate the strength of tidal effects. We also emphasize that the effect of ocean loading is an important component of the earth tide, and cannot be neglected in a study of tidal triggerings of earthquakes.
著者
大村 纂
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.121, no.4, pp.626-634, 2012

&emsp;The article presents a summary of the development of geography in Switzerland since the late 19th century. After initial development placed weight on physical geography, there was a period after the Second World War until the early 1970s when human geography blossomed, mainly because of the need for regional planning. During the 1970s, geography in Switzerland searched for a new direction either as an environmental science or as a part of the Earth sciences. In a method-oriented development, satellite-based remote sensing and computer-based Geographic Information System were actively introduced. During the last thirty years, the field of physical geography has been productive, while human geography has failed to establish itself either as an environmental science or a scientific discipline with a global perspective. Notable accomplishments at universities in Berne and Zurich, as well as at the Federal Institute of Technology (E.T.H.), are summarized. Coordinated contributions that are internationally acknowledged have been made in various fields of climatology and geomorphology. Furthermore, the teaching of geography at Swiss high schools and teaching training methods at universities are outlined.
著者
小俣 利男
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.121, no.4, pp.699-716, 2012

&emsp;The discipline of geography in Russia has evolved during the twenty years since the systemic transformation of Russia following the collapse of the Soviet Union. Viewed from a historical perspective, geography has undergone distinct changes throughout the Imperial, Soviet, and current Russian eras. In this sense, the history of geography in Russia is richer and more complex than it may seem at first glance. When discussing the present situation of geography in Russia, it is important to consider historical continuity and discontinuity. Accordingly, this paper examines the present situation of geography in Russia, partly by adopting a historical approach, based primarily on previous literature.<br>&emsp;The following main characteristics of geography in Russia were identified. Russia has two kinds of scientific center&mdash;the Academy of Sciences and the universities&mdash;in addition to its famous Geographical Society and large national territory. As a result, Russia has become one of the world leaders in the fields of geography and geographical education. Russian geography includes a wide range of fields of geography, known in Russia as the &ldquo;geographical sciences,&rdquo; and has experienced ecologization since the late 1970s. The influence of the systemic transformation on geography, although it varies by field, has not completely ceased today. Recently, new sources of support for the development of geography have emerged. One of the factors involved in most of the above-mentioned characteristics is the relationship between geography and the government. This concept is used to explain changes in the discipline of geography from the Imperial era to the present.
著者
中西 正男
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.126, no.2, pp.125-146, 2017
被引用文献数
4

<p> A newly compiled bathymetric map including parts of the Kuril, Japan, and northern Izu–Ogasawara trenches in the northwestern Pacific Ocean demonstrates that most bending-related topographic structures are limited to less than 80 km from the trench axis. This observation contrasts with one that bending-related structures of eastern Pacific trenches are limited to less than 50 km from the trench axis. The discrepancy may be due to differences in the ages of subducting oceanic plates. Bending-related topographic structures of the western Kuril and southern Japan trenches are not parallel to the trench axis, but instead are parallel to magnetic anomaly lineations. Those of the northern Izu–Ogasawara Trench are parallel to fracture zones. These observations indicate the rule that the inherited seafloor spreading fabric is reactivated instead of forming new faults when the degree of obliquity between inherited seafloor spreading fabric and trench axis reaches about 30°. This rule is applicable to most trenches around the Pacific Ocean, except for some parts of curved trenches and trenches near seamounts or other volcanic edifices constructed by off-ridge volcanism. Most bending-related topographic structures near off-ridge volcanic edifices are parallel to the trench axis. This observation suggests that inherited seafloor spreading fabric around the volcanic edifies was disrupted by volcanism.</p>
著者
杉本 興運 小池 拓矢
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.124, no.6, pp.1015-1031, 2015
被引用文献数
4

&emsp;This study examines tourist behavior in the Mt. Fuji area in terms of distance traveled by tourists, and clarifies differences in types of tourist and their movements based on distance traveled. Moreover, it describes the social impact of the area's recognition as a UNESCO World Heritage site on the behavior of tourists. Tourism in the Mt. Fuji area began as Fuji Tohai, which means &ldquo;climbing for worship&rdquo; in the Edo era, and was popularized by subsequent tourism development. At present, the Fuji area is a tourism region that provides opportunities for sightseeing, leisure, and recreational activities, such as exploring and staying in the Fuji Five Lakes region, to visitors who live in or near urban and metropolitan areas. By analyzing the results of a questionnaire survey given to domestic individual travelers who use private cars, we found that their behavior is characterized by differences related to travel distance, although most of them share the common purpose of experiencing natural landscapes during their travels. Neighborhood residents tend to visit for daily leisure activities, whereas visitors from distant places tend to make overnight trips and visit only major tourist attractions. This shows the nature of the concentric model, which means that travel distance influences the behavior of tourists, their perceptions, and frequency of trips, and vice versa. However, we simultaneously discovered a distortion in this model, which is caused by the locality of the Mt. Fuji area. Tourism in the Mt. Fuji area currently faces changes resulting from the significant social impact of the area's recognition as a World Heritage site: Tourism demand is increasing, especially among persons who live in more distant places, which means foreigners living abroad in this study, and local residents are working to develop tourist areas and touring routes, focusing on World Heritage. Tourist behavior, such as perception and movements, have gradually changed in parallel with social and environmental changes.
著者
川畑 幸夫
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.61, no.4, pp.121-125, 1953

In this paper the author summarized the researches done in Japan on the relation between sunspots and meteorological phenomena.<BR>The idea common to almost all the researchers is that the sunspots as an index of solar activity cause the variations of atmospheric pressure on the earth namely, as the conditions of the earth's atmosphere which receives solar radiation are varying according to seasons and locations, the changes in solar radiation due to sunspots cause the variations of the distribution of atmospheric pressure, which result in disturbances of air currents and in climatic variations. And these disturbances are almost strongly effected, in Japan, by the changes in the intensity of the North Pacific High and by the migration of its center.<BR>A few Japanese researchers are making use of the faculae instead of sunspots in their researches, and they consider the degree of the faculae's facing to the earch as the solar activity index, and this consideration seems to be an excellent one perhaps unseen in other countries.
著者
安里 進
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.105, no.3, pp.364-371, 1996-06-25
参考文献数
33

Is it possible that modern Ryukyuans are the descendants of Palaeolithic Minatogawa Man, and the people of the Shellmound Period, which is partially equivalentto the Jomon Period ? There is a blank period of about 10, 000 years between the Minatogawa population and the population of the Okinawan Shellmound Period. Sakishima prehistoric culture was one of the Southeast Asian prehistoric cultures until the beginning of the Heian Period. A dramatic cultural change occurred in Okinawa after the Shellmound Period, in the Gusuku Period, which began in the 10th to 11th centuries as a result of culturalinfluence from the Mediaeval Period of Kyushu. Darling 13th to 14th centuries the culture of the Gusuku Period also expanded into the Ryukyu Islands from Amami Islands to the Sakishima Islands, and there was a general rapid population increase. Modern Ryukyuans are descended from the populations of the Gusuku Period. Some geneticists and anthropologists insists that modern Ryukyuans possess hereditary blood factors found in northern Asian populations. It is suggested that those factors flowed into the Ryukyuan population in the Gusuku Period.