Correlation 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.
The 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.
Geographical 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.
The 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.
The 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).
The 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.