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Volume 103, Issue 3
Displaying 1-16 of 16 articles from this issue
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Akio YOSHIDA1994 Volume 103 Issue 3 Pages 201-206
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
JOURNAL FREE ACCESSCorrelation between earthquakes in Kanto region and intermediate-depth earthquakes in Hida region, central Japan is re-investigated. We found that a significant correlation exists between earthquakes with depth of 70 km and deeper in western Kanto and intermediate-depth earthquakes in Hida region, but such a correlation is not seen for earthquakes in eastern Kanto. This result shows that earthquakes occurring in the Pacific slab are well correlated each other, but earthquakes which occur in relation to the subduction of the Philippine Sea plate are not correlated with intermediate-depth earthquakes in the Pacific plate. Intermediate-depth earthquakes in Hida region have a tendency to precede earthquakes in western Kanto. This feature may be related to the dynamics of the plate motion which oceanic plate is pulled by the subducted slab.View full abstractDownload PDF (1029K) -
Poly-generation volcanoKenji HAYATSU, Satoshi SHIMIZU, Tetsumaru ITAYA1994 Volume 103 Issue 3 Pages 207-220
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
JOURNAL FREE ACCESSThe Myoko volcano group, consisting of five stratovolcanoes, Myoko, Kurohime, Iizuna, Yakeyama and Madarao, is situated in the northern part of central Japan. Twenty one volcanic rocks from the early stage of volcanic successions of Myoko (5 samples), Kurohime (4 samples), Iizuna (9 samples) and Madarao (3 samples) were dated with K-Ar methods. On the basis of previously well studied geology and petrology of the volcano group and chronology of marker tephra layers in this area together with newly obtained K-Ar ages, volcanic history of the Myoko volcano group was discussed in detail. The results confirmed the genetical story of the volcanoes by Hayatsu (1985), i. e., the Myoko volcano has grown by four stages of active volcanisms with three distinctive pauses and each stage has a chemical fractionation trend from basalt to dacite through andesite during a volcanism, and other volcanoes were also in the same story though number of stages was variable : three for Kurohime and two for Iizuna and Madarao, and the fractionation trend was little changeable. This paper calls this type of volcano “poly-generation volcano”.
Growth mechanism of the poly-generation volcano was also revealed in detail : life span of each generation, that is time span of each stage of activity, is nearly constant, 20-50 kyrs though some exceptions but total amount of volcanic ejecta decreases with time, e. g., 40-20-7-5 km3 for Myoko, and pause period between any two active volcanic stages decreases with time from 100-160 kyrs of early pause to ca. 10 kyrs of late one.
This poly-generation volcano is common in Japan and should be studied in further detail from view points of igenous petrology and tectonics of magmatism as well as geothermal energy and volcanic hazards.View full abstractDownload PDF (2733K) -
A case study in Kanazawa CityYoshiki WAKABAYASHI, Satoru ITOH1994 Volume 103 Issue 3 Pages 221-232
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
JOURNAL FREE ACCESSGeographical approach to cognitive maps has mainly focused on measurement of their spatial patterns. Recently Lloyd (1989) devised a useful method for analyzing the components of distortions in cognitive maps by means of Euclidean regression. Until now, however, this method has not yet been validated. The purpose of this study was to reexamine his concepts about the distortions in cognitive maps and to test their validity.
We pointed out several discrepancies between the concepts of distortions and their operational definitions given by Lloyd (1989). To overcome this problem, the absolute distortion that appears in the configuration before Euclidean regression ought to be distinguished from the systematic distortion that is measured by the parameters of Euclidean regression. While the systematic distortion that indicates a Euclidean property of the distortion can be explained by alignment and rotation heuristics (Tversky, 1981) and implicit scaling model (Holyoak and Mah, 1982), the relative distortion that remains after Euclidean regression cannot be explained by general theories. In addition, these geometrical components of distortion ought to be distinguished from statistical ones, namely, distortion (central tendency) and fuzziness (dispersion) defined by Gale (1982).
On the basis of this conceptualization, we carried out an empirical analysis of the distortion in the cognitive map of Kanazawa City. The data used in this study were obtained by a conditional sketch mapping drawn from 113 students of Kanazawa University. Locations to be answered were 21 transportation nodes within the central part of the city known by more than 90 percent of the students. From these locations, two major landmarks of CBD were selected as reference points. Subjects were asked to indicate the remaining 19 locations on the legal-size sheet in which the two reference points were printed.
We detected the absolute distortions, overlaying the cognitive maps for all samples on the actual map so as to fit the locations of two reference points into the actual ones. The patterns of the absolute distortion indicated that the amount of errors increased with distance from the reference points, and that the locations in cognitive maps commonly shifted outward from the actual ones. Specifically, these displaced locations in southern or eastern part of the city indicated a counterclockwise shift, which suggested a directional bias in cognitive maps.
In order to separate the systematic distortion from the relative one, each of the cognitive configurations was fitted into the actual map by Euclidean regression. Parameter estimates of the scale change averaged 0.593, which suggested that cognitive maps were enlarged about twice the size of the actual map. Mean direction of the rotated angle amounted to-22.2 degrees, which implied that cognitive maps were rotated counterclockwise about 20 degrees from the actual map so as to coordinate the cardinal directions of the cognitive map with the actual one. This tendency can be due to the displacement of two river channels as major reference lines in Kanazawa from cardinal directions.
After eliminating the systematic distortions by Euclidean regression, the actual map was overlaid with all the cognitive maps. The overlaid maps indicated that the local patterns of relative distortions reflected hierarchical structure of cognitive maps (Stevens and Coupe, 1978) although the amount of them was smaller than that of the systematic distortions.View full abstractDownload PDF (2215K) -
Sedimentary environment in Mikata Lowland since the last interglacial timeKeiji TAKEMURA, Hiroyuki KITAGAWA, Akira HAYASHIDA, Yoshinori YASUDA1994 Volume 103 Issue 3 Pages 233-242
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
JOURNAL FREE ACCESSThe sediments of Mikata Lowland (including Mikata Five Lakes), central Japan, contain a potential record of paleoenvironments and paleoclimates that date since the last interglacial time. Three continuous drill cores of lake and fluvial sediments in Mikata Lowland were obtained in 1991-1993, from Lake Mikata, Lake Suigetsu and Kurota Lowland. Dating of core samples by a combination of tephrochronology and 14C dating has revealed that three core samples include the paleoenvironmental history since at least the most recent interglacial time. The sedimentation process in Mikata Lowland has also been clarified by the sedimentary facies of core samples. The average sedimentation rate in Lake Mikata is twice as large as in Kurota Lowland which situated at the southern part of Mikata Lowland.View full abstractDownload PDF (2125K) -
Yoko OTA, Satoko ODAGIRI1994 Volume 103 Issue 3 Pages 243-267
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
JOURNAL FREE ACCESSThis paper aims to establish the late Quaternary chronology of marine terraces and pattern and rate of late Quaternary tectonic deformation of a coastal area over ca. 50 km long from Cape Ino to Cape Ashizuri along the Tosa Bay, based on late Pleistocene and Holocene marine terrace data. This area is close to the Nankai Trough on the boundary between the Philippine Sea plate and Eurasia plate, and is known as a seismically active area.
Marine terraces are classified into Hi, H2, H3, M and L terraces in descending order. The M terrace is identified as the last interglacial terrace that corresponds to oxygen isotope stage 5e with an age of ca. 125 ka, judging by the following evidences : 1) This terrace is the most continuous, and has the best-preserved surface ; 2) It is underlain by relatively thick (up to 20 m) transgressive deposits in the vicinity of large river mouths, indicating that it formed in association with a rising sea level ; 3) Amino acid ratio of shells in the transgressive deposits implies an age of ca. 138ka (Mitsushio et al., 1989); and 4) Dune sand overlying the terrace surface includes K-Tz tephra of ca. 75-95 ka BP, demonstrating that the emergence of the M terrace surface was older than this age.
A eustatic origin is also inferred for the formation of H2 and H1 terraces, which are continuously traced within the study area. Judging by the close positive relationship between the former shoreline height of M terrace and that for H1 and H2 terraces, the ages for H1 and H2 terraces are estimated to be ca. 270 ka and 176 ka, respectively, although no direct evidence was obtained for the age determination of these high terraces. L terrace is Holocene in age and is subdivided into at least 3, and possibly 4 steps, implying that episodic uplift has repeated during the Holocene. Li, the highest Holocene terrace, represents the culmination of Holocene sea level rise and L3 is dated at ca. 500-700 yr BP, older than the last 1946 coseismic uplilt of ca. 0.4 m along the western part of the Ashizuri Peninsula.
The former shoreline of the M terrace now ranges in height from 20 m to 75 m with generaly northwestward (landward) downtilting. The study area can be subdivided into two subregions, Cape Ino subregion and Ashizuri subregion, both of which also tilt northwestward, when we consider that the abnormally low height at the northern margin of the Ashizuri Peninsula is an extension of Cape Ino fault, which represents one of subsidary faults from the main subduction thrust (Kato, 1983). The causative subsidary fault which is responsible for the tilting of Ashizuri subregion is not identified, however. Progressive northwestward tilting is obvious from the former shoreline height of the older terraces. L terrace also tilts northwestward. Therefore it can be said that this coastal area has been affected by the same pattern of deformation by movements of at least two subsidary faults for the last ca. 300 ka, since the estimated time of formation of the oldest terrace (H1).View full abstractDownload PDF (5039K) -
Kotaro YAMAGATA1994 Volume 103 Issue 3 Pages 268-285
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
JOURNAL FREE ACCESSThe surrounding area of the Shikotsu and the Kuttara volcanoes, and Ishikari-Lowland, in the southwestern Hokkaido, are covered with thick pyroclastic deposits of the late Pleistocene. These pyroclastic deposits have been subdivided into units according to facies changes. consequently each unit does not necessarily represented a single eruption. In the present paper, the products of one eruption (tephra formations) are separated from one another by recognition of intervening “volcanic ash soils” which are considered to be the most suitable for indicating quiet period, owing to its low depositional rate and generality.
In the Ishikari-Lowland, the previously defined two groups of tephra formations (En-c and Spfl · Spfa 1; Spfa 7, 8, 9 and 10) are reinterpreted to represent the products of two eruptions, because the volcanic ash soils are absent among them. And three tephra formations are newly recognized. Twenty two tephra formations constitute the late Pleistocene pyroclastic deposits in the Ishikari-Lowland.
The pyroclastic deposits distributed around the Kuttara volcano are subdivided into twelve tephra formations and one scoria fall group. The tephra formations derived from the Kuttara volcano are as follows in ascending order : Kt-8, 7, 6, 5, 4, Kt-Hy, Kt-3, Kt-Tk scoria fall group, Kt-2, Kt-1. The Kt-8 …-1 are mainly composed of plinian pumice fall deposits and pumice flow deposits generated by large and moderate scale explosive eruptions.
The correlation of the tephra formations in the surrounding area of the Kuttara volcano and the Ishikari-Lowland is attempted with several petrographic parameters and stratigraphic position. The following tephra formations are correlated each other : Kt-8 and Aafa 1, Kt-5 and Mpfa 2b, Kt-4 and Mpfa 2a, Kt-3 and Spfa 4, Kt-Tk and Spfa 3, Kt-1 and Spfa 2. In addition, it is proved that the following tephra formations spread to the Ishikari-Lowland : Kt-7, Kt-Hy, Nj-Os.
On the Shikotsu volcano, three explosive eruptions preceded a large scale caldera forming eruption (Spfl · Spfa 1 : Ca. 32 ka), and after a short repose time, present post caldera activity started. The Kuttara Volcano was the site of seven explosive eruptions during the period from 70-40 ka ; then the stratovolcano was formed by erupting Kt-Tk scoria fall group, and the summit caldera was formed by the last two explosive eruption (Kt-1 and 2).View full abstractDownload PDF (3601K) -
Chousei SHIMIZU, Yoshitsugu SUZUKI1994 Volume 103 Issue 3 Pages 286-294
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
JOURNAL FREE ACCESSThe forest limit is defined in this paper as a line which divides such scrubs as Pinus pumila from subalpine coniferous forests. Usually, control factors which determine the position of forest limits are temperature, wind, snow depth, slope form, and soil condition, and so forth. In this paper, effects of slope deposit and soil condition of the forest limit were discussed.
Mt. Kinpu-san (2, 595 m; 35°52'N) in Central Japan consists of granitic rocks. The forest limit on the slopes around summit ranges from 2, 280 to 2.570 m in altitude. It was found the periglacial block slope formed during the late stage of the Last Glacial age at higher than 2, 280 m in altitude around the summit. The surface of this slope is composed almost entirely of matrix-free blocks (0.5 to 6.0 m in diameter) covered with thin soil. The site condition on such slopes has halted forest from developing but to support the scrub. On the other hand, the periglacial block slope of the early Last Glacial age was distributed in lower altitudes than the younger one. Subalpine coniferous forests was developed on this older slope covered with thick soil. The forest limit is situated below the small cliff formed at the terminal of the younger periglacial block slope. From these facts we conclude that the local forest limit in this area is forced to be located in the margin of younger periglacial block slopes.View full abstractDownload PDF (1704K) -
Takaaki KAWASUMI1994 Volume 103 Issue 3 Pages 295-300
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
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[in Japanese]1994 Volume 103 Issue 3 Pages 301
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
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[in Japanese]1994 Volume 103 Issue 3 Pages 301a
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
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[in Japanese]1994 Volume 103 Issue 3 Pages 301b-302
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
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[in Japanese]1994 Volume 103 Issue 3 Pages 302
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
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1994 Volume 103 Issue 3 Pages 302a
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
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[in Japanese], [in Japanese]1994 Volume 103 Issue 3 Pages 303-305
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
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[in Japanese]1994 Volume 103 Issue 3 Pages Plate1-Plate2
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
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Chousei SHIMIZU1994 Volume 103 Issue 3 Pages Plate3-Plate4
Published: June 25, 1994
Released on J-STAGE: November 12, 2009
JOURNAL FREE ACCESSDownload PDF (8165K)
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