Surface weather charts have been analyzed nearly for one century on a hemisphere scale. The present study tries to demonstrate characteristics of the occurrence frequency of pressure patterns in the global cold, warm, and recent variable periods, which correspond to or are responsible for anomalies in air temperature and precipitation, and to investigate the intraseasonal variations and singularities of pressure patterns over East Asia. This study defines the period from 1906 to 1920 as a cold period, that from 1936 to 1950 as a warm period, and that from 1971 to 1985 as a recent variable period. According to the classification of pressure pattern types by Yoshino (1968), a calendar of pressure patterns during the periods 1906-1920 and 1936-1940 was originally made on the basis of “Daily Synoptic Series, Historical Weather Maps, Northern Hemisphere Sea Level”. The statistics of this study are also based on the calendars for the periods 1941-1950 (Yoshino and Kai, 1974), 1971-1980 (Yoshino and Yamakawa, 1985) and 1981-1985 (original). The results of this paper are summarized as follows : The annual frequency of the typical winter type (type W) of west high and east low does not reveal much difference between the cold and warm periods. However, in the warm period, the duration of Type W appearance is shorter, but it occurs more frequently in January than in that of the cold period. The typical summer type (Type S), south high and north low, is most distinguished in August, though it is perceptible from July, in the warm period. The temperate migratory high type (Type H) (excluding highs passing North Japan) is clearly eminent throughout the year in the warm period. Particularly in April, Type H accounts for 43% (13% more than that of the cold period); in October it forms 37% (16% more). In the warm period, singularities of Type H are recorded five times in spring and autumn seasons, respectively. The north high type (Type N), which includes migratory highs in North Japan, southern coastal lows and southern coastal fronts, appears with low frequency in the warm period. The difference in occurrence frequency of Type N between the both periods is large in spring (April, May) and autumn (Sept., Oct.). In the cold period when the onset and end of the Baiu season are quite clear, the frontal zone type, consisting of Types N and L, appears with very high frequency (about 90%) throughout the Baiu season. With regard to the typhoon type (Type T), it tends to appear more frequently in August and September of the cold period ; in October of the warm period. Type T appears less frequently in both the summer and autumn seasons of the recent variable periods. Ratios of anticyclonic singularities to cyclonicones are 43 to 57 in the cold period, 54 to 46 in the warm period and 42 to 58 in the recent variable period. In the last period there are many identical singularities with those in the warm period. Especially from mid-August (Aug. 14-18) to mid-September (Sept. 8-12), a series of common singularities-Types T, S, L, S, L and L-are recognized in this order both in the warm and recent variable periods.
The Tsurumi River, noted for its frequent inundations, was not within the scope of the national or prefectural flood control programs in the Meiji era, because the Tsurumi River was too short to be covered by the national flood control policies under the old River Act after 1886. Flood control works for the Tsurumi River were left to private activities at the expense of the local land owners in the Meiji era. The Water Use and Reclamation Cooperative, which was founded in 1888 for the middle and lower reaches of the Tsurumi River, remained inactive and failed to develop either to a more organized water use cooperative or to a flood prevention cooperative in the Meiji era, mainly because of a substantial regional diversity of water use and flood risk. Among the various local flood control works, two types of sharing expenses have been identified through the fieldwork. The first and main type was applied to many smaller works, where shares were not equal and owners or users of the land at the outer side of the banks bore much more than those at the inner side of the banks. The second and minor type was applied to larger works, where total expense was almost equally shared by all the land owners or users involved, by land area or by per capita base. The serious floods at the end of the Meiji era (the late 1900's) was a turning point which resulted in the construction of modern banks at the middle reaches of the Tsurumi River by Kanagawa Prefectural Government, although a heavy burden to the local land owners was involved. The heavy share to the local people was also applied to the flood control expenses at the beginning of the Taisho era (the 1910's) for the Tama River, which affected the Tsurumi River Basin as well as the lower reaches of the Tama River. The local people in the middle and lower reaches of the Tsurumi River organized the Tsurumi River Union in the early 1920's, to campaign for flood control works at the expense of the national government, which was eventually realized in the 1930's. The running cost of the union was shared by the villages involved according to the flood damage at the end of the Meiji era. The regional diversity of flood risk resulted in unequal shares of flood control expenses. The system of unequal imposition continued for a long time until the major flood control works at the public expenses were realized.
Widespread Tephra is a valuable time marker for tephrochronology and archaeology. Several fine ash fall deposit are distributed in central and northern part of Miyagi Pref. The authors have correlated them to widespread tephras by means of following methods. They are lithological description of tephras, measurements of refractive indices of glass shards and heavy minerals, and analyses of major elements chemical composition of glass shards using a microprobe analyzer. As a results, four late Pleistocene widespr ead tephras are discovered in this study area. They are AT, Aso-4, On-PmI and Toya. The authors described the stratigraphic positions of those widespread tephras in detail. And furthermore, they mentioned the significance that four late Pleistocene widespread tephras were discovered in this study area. The results are summarized as follows. 1) In central part of Miyagi Pref., the stratigrafic sequence of AT ash, Kawasaki scoria layer, Aso-4 ash and Medeshima pumice layer occur in ascending order is confirmed. Kawasaki scoria and Medeshima Pumice are valuable marker tephras in that region. In northern part of Miyagi Pref., 10 tephras or tephra formations and their stratigraphic positions are recognized. They are, in ascending order, Hijiori pumice layer, Narugo·Katanuma-Uehara tephra, AT ash, Narugo-Yanagisawa tephra layer, Aso-4, Narugo-Nisaka tephra layer, Kitahara ash layer, On-PmI, Toya ash and Ichihasama pumice layer. Consequently, the late Pleistocene tephra stratigraphy in Miyagi Prefecture is linked with those in central and southwestern part of Japan. 2) The stratigraphic relation between On-PmI and Toya ash is revealed for the first time to implicate the occurrence of marine terrace developed in ca 100 ka in a tectonically active region.
The Izu-Bonin intra-oceanic island arc-trench system is a product of the subduction of Pacific lithosphere since the Eocene. The purposes of Ocean Drilling Program (ODP) Leg 126 were to study the following three important and poorly understood aspects of this system, namely (1) the origin and evolution of the forearc basin, investigated by drilling a series of holes through the sediment piles and into the basement of the forearc basin (Sites 787 and 792-793); (2) the process and products of arc rifting, investigated by drilling holes into the center (Sites 790/791) and eastern footwall (Sites 788/789) of the Sumisu backarc depression ; and (3) recycling of subducted lithosphere and evolution of the mantle, investigated indirectly from the composition of the volcanic rocks as well as volcaniclastics recovered from all sites. The principal drilling results of Leg 126 show that the forearc basin formed about 35-30 Ma by separation of the formerly contiguous frontal and outer arc highs. Igneous basement beneath the center of the forearc basin includes high-Mg andesites, andesites with boninitic affinities, and low-Mg tholeiitic lavas. The forearc basin was rapidly buried immediately after its formation with volcaniclastic turbidites and debris flow deposits in the late Oligocene age. Following a minimum of volcanic output between 24 and 13 Ma, there has been a steady increase in explosive volcanic materials in the forearc with a dramatic increase in the late Quaternary. Paleomagnetic evidence shows that the forearc has been northwardly translated about 15° since 30 Ma. Benthic foraminiferal assemblage data suggest 1-2km of basement uplift has occurred since the mid-Oligocene. Pore waters in the Oligocene volcanogenic sediments of the forearc basin are the most extensively altered pore water of seawater origin ever sampled by DSDP/ODP. Low-temperature alteration of the volcanogenic sediments has produced fluids extremely enriched in Ca and depleted in Mg, Si and sulfate. The present stage of rifting together with deep sea explosive volcanic eruption of the basaltic mousse in the backarc Sumisu Rift at 31°N began between 3.56 and 1.1 Ma with both present-day and pre-rift volcanism along the volcanic front dominated by rhyolitic pumice eruptions. The footwall of the Sumisu Rift has been uplifted 200-1700m, and rift basement depth prior to 1.1 Ma exceeded 2 km. The basement of the rift is formed by early rift basaltic lavas and intrusives, as well as by arc pyroclastics metamorphosed to zeolite to greenschist facies. Bimodal volcanic activity with intra-rift basaltic eruptions (basaltic mousse) and rhyolitic eruptions was common but explosive arc volcanic activity dramatically increased 200 ka. at the Sumisu and South Sumisu Calderas along the volcanic front. Unlike the forearc region, fluids other than sea water are not circulating locally through the sediments in the Sumisu Rift.
Comprehending patterns of raw material utilization for stone implements can be a key to the solution of questions concerning cultural tradition, cultural behavior, culture areas and trade in prehistoric times. The materials of stone implements reflected “knowledge of requirements (specificastion)” of the tool-makers, and this point is exemplified by stone implements of the Middle Jomon period, the Neolithic period in Japan. Patterns of raw material utilization for stone implements, at that time, were different among tool types. Evidence is presented which supports the view that Jomon people intentionally selected raw materials according to their “knowledge of tool requirements” (relating to the size and the shape of the tools). In addition, utilization of raw materials for sometypes of stone tools varied between districts. However, such differences confirmed to the intentional hypothesis. Eight types of stone implements in the Middle Jomon period, arrowheads (sekizoku), drills (ishikiri), points (sentouki, sentoujyousekki), pounding stones (tatakiishi), ground or pitted stones (suriishi, kubomiishi), querns (ishizara), roughly chipped ax-like stone tools (daseisekifu) and polished ax-like stone tools (maseisekifu), have been divided into three categories (1, 2, 3) according to the pattern of raw material utilization. Category 1 : Arrowheads, drills and points. All these are small light thin and sharp pointed tools which were made from thin flakes and hard compact silicious materials, predominantly obsidian or shale. There were two regional spheres of raw material utilization, the shale area and the obsidian area. Near the producing areas of obsidian in Chubu and Kanto districts, Jomon people tended to use this material. However, in the shale producing district, Tohoku district, Jomon people used often shale (silicious shale and hard shale). Category 2 : Pounding stones, ground or pitted stones, and querns. These stone implements are big heavy round lumpish tools which were made from round stones and primarily either andesite or sandstone. In every site in Eastern Honshu, these implements were predominantly made of one of these two rock types regardless of region. In addition, such characteristic materials used for category 1, such as obsidian and shale (silicious shale or hard shale), were rarely utilized for this category. Category 3 : Roughly chipped ax-like stone tools and polished ax-like stone tools. These are the middle weight-thickness implements for which various kinds of raw materials were used, except for obsidian and shale (silicious shale or hard shale). The typical regional patterns of raw material utilization could not be found among the sites.