Several hundred years of astronomical observations have left no doubt that the Earth's orbit is subject to cyclic variations. While the annual energy receipt of solar radiation over the Earth as a whole is not change, the distribution of this energy, by latitude and by season, is affected by three parameters: an obliquity cycle of 41kyr, an eccentricity cycle of a quasi-period of 100kyr, and a precession cycle of 26kyr. The variance spectrum of the records of foraminiferal δ18O and magnetic susceptibility from Indian Ocean and organic carbon percentage from the equatorial regions of Pacific and Atlantic Oceans shows the well-documented concentrations of power at the orbital periodicities of 100kyr, 41kyr and near 23 and 19kyr. On the other hand, the resolution of the precessional bands in carbonate dissolution index is much less clear than those of obliquity and eccentricity bands. These results show that orbital forcing of global climate has strongly affected global carbon cycle. Detailed analysis of coherency and phase spectrum between δ18O and carbon-related data (i. e., carbon contents and isotopic composition) will improve our understanding global carbon cycle.
Hydrothermal flux from mid-oceanic ridges and back arc basins influences global seawater chemistry. For instance, Mg problem (Dreyer, 1974) can be solved by taking into account of Mguptake from seawater due to the interaction of seawater with oceanic crust under hydrothermal conditions. SO42-also removes considerably from seawater to oceanic crust. Ca, Si and K transfer from oceanic crust to seawater. This interaction takes place not only at mid-oceanic ridge axis, but also at mid-oceanic ridge flank system. The influence of hydrothermal flux from present-day back arc basins on seawater chemistry is small, compared with that of midoceanic ridges. However, hydrothermal flux from back arc basins in Circum Pacific region during middle Miocene (25-15 Ma)(e. g. Green tuff activity) is large. Especially, hydrothermal fluxes of volatile elements (S, As, Sb, Bi, Cl) from back arc basins are large, compared with the hydrothermal fluxes from mid-oceanic ridges. It is concluded that global seawater chemistry is controlled not only by exogenic processes (e. g. river input, sedimentation) but also by endogenic processes (e. g. hydrothermal activity).
The concentration of an illiterate population in the capital city is one of the common phenomenain developing countries, such as the Republic of Panama. Few studies have triedto examine socio-demographic factors and their effect on regulating the social space of literacyin the urban areas of developing countries. This paper, using 1990 census data at the neighborhoodlevel, tried to identify some factors concerning the spacial differentiation of literacyin Panama City, and attempted to analyze how the extracted factors affect the literacyrate. From observing the spacial differentiation pattern in the literacy rate (Fig. 2), highrate areas, in the central and intermediate zones of Panama City, appear near the centralbusiness district and elite residential zone. Apart from the city center, high rate areasexpand along the two principal highways, la Carretera Transismica and la Carretera Panamericana.Although, in the area along la Carretera Transismica, the high rate area is interruptedin the north-east part of Betania, in the area along la Carretera Panamericana it extendscontinuously to the east fringe of Panama City. The low rate areas, in the central zone, correspond to the urban slums, such as Crundu, Baca la Caja, Panama Viejo, and MonteOscuro, which have grown out of squatter settlements. Moreover in the suburban zone, lowrate areas appear in the widespread zone of the San Miguelito District and in the Pedregal'snorth-east hilly zone. As mentioned above, it is hypothesized that this spatial differentiationof the literacy rate in Panama City may correlate with certain socio-economic indices. To examine the relationship between the literacy rate and these socio-economic aspects, 22variables representing the population's economic status, housing status, and educational statuswere prepared (Table 1). Next, a stepwise multiple regression analysis was carried out.Six variables were selected as the independent variables (Table 2). These are the employmentrate, the patron rate, the individual income, the rate of housing built during 1980-1990, theschooling years, and the school enrollment rate of the population from ages six to fifteen. To clarify the causal relationship between literacy rate and selectd variables, a pathanalysis was carried out. From the path diagram, which was composed from the literacy rate and economic status indices, it is possible to describe a causal relationship between the liter acyrate and economic status variables, although this relationship is not particularly clear (Fig.3). However, in the path diagram that includes educational status variables, it is clearfrom Fig. 4 that schooling years are the best explained as a dependent variable and as animportant direct influence on the literacy rate. The correlation of the literacy rate witheconomic development indices has been widely mentioned, and in this study it is concludedthat this relationship is clearer when observed via educational status, such as schooling years. Two areal groups divided by individual income were analyzed separately to ex aminethis relationship with respect to differing development levels (Fig. 5). A strong relationshipbetween the selected variables was confirmed for the low income area (Fig. 6). For the highincome area, the same relationship was observed, but much more weakly, with only thepath coefficient of employment rate and individual income being worthy of note (Fig. 7).These results suggest the importance of economic, educational upward mobility in the lowincome area, and employment stability in the high income area, as critical factors in influencing the literacy rate.
A multi-disciplinary synthesis was made on the tectonics and seismotectonics in the northwestern Sagami Bay and adjacent areas, where the plate boundary between the Izu-Bonin and Northeast Japan arcs passes and historical M7-8 inter-and intraplate earthquakes frequentlyhave occurred. In a convergent boundary between plates, a displacement between plates is usually accommodatedalong a broad belt of active imbricated thrusts and folds, which develop in a wedge ofan overriding plate. In such a situation, we can easily identify two kinds of plate boundaries: a deformation front and a subduction entrance. The deformation front is a line connecting thethrusts or folds nearest to a trench/trough axis. The subduction entrance is a line connecting theedges of trench/trough filling coarse deposits, which cover a surface of a subducting plate. In Sagami Bay, the deformation front in the overriding Northeast Japan arc is estimated to belocated along the northern and eastern edges of the Sagami Basin, while the subductionentrance of the subducting Izu-Bonin arc is estimated to be located along the southern edge of the Basin. Many geomorphological, geological, geophysical observations need and support the existenceof the West Sagami Bay Fracture (WSBF), an intraplate propagating fracture between the Izu-Bonin outer and inner arcs, proposed by Ishibashi (1988), whereas these observations require slightmodification of the estimated geometry around the WSBF. Frequent dike intrusions in theHigashi Izu monogenetic volcano field cause spreading of the upper crust and probably move the Manazuru “microplate”(MNZ) to the NNE direction against the Izu block. The Tanna-Hirayama tectonic line is proposed as a transform fault, which accomodates the relativemovement between the MNZ and the Izu block. In the MNZ hypothesis, the Kozu-Matsuda fault, located to the northeast of the Izu Peninsula, is interpreted as a deformation front between theoverriding Northeast Japan arc and the MNZ, which is buoyantly subducting beneath the Oiso Hilland Tanzawa Mountains. The proposed new geometry around the WSBF and the hypothesis of the MNZ can explain (1) the crustal structure and tectonic features around the Kozu-Matsudafault, (2) tectonic implication of the “Oiso-type” earthquakes, which are expected to displacethe Kozu-Matsuda fault periodically, and (3) the rapid upheaval of the Tanzawa Mountains since 1Ma.
Mineralogical characteristics of last 2, 000 year records in a meromictic lake, Lake Suigetsu, are the indicators of eolian dust concentrations, sea-level and rainfall changes in central Japan.Lake Suigetsu sediment records shows that there was no large influx of terrestrial materials intolake basin. Sequential changes of illite crystallinity and quartz/illite ratio in Late Quaternaryfine-grained sediments at Site 794 and Site 795 of ODP Leg 127 of were well correlated tostandard recocds of oxygen isotope change by Prell et al.(1986). This suggests that theseparameters are useful to detect eolian dust concentration within sediments. In other words, occurrence of hydrated illite and small concentration of illite suggest that paleosols were greatlyformed under wet climate in northern China. Sea-level and rainfall changes were detected byiron mineral compositon and chlorite/illite ratio.Investigations show that climatic changes in northern China were parallel to sea-levelchanges of the Wakasa Bay in southern part of the Japan Sea. In 250, 820, 1170, 1320, 1500and 1889 A.D., sea-level was risen in the Wakasa Bay when northern China was in wetclimate. It is because that Asian monsoon was active in globally warm cliate at these times, andthat active monsoon took humid atmosphere into northern China. In 250, 820, 1050-1200, 1320, 1500 and 1880 A.D., there seems to have been heavy rainfall around Lake Suigetsu with sea-levelrising in the Wakasa Bay. This suggests of influxing of Tsushima Current, supplying humidatmosphere and rising of sea-level. In 350-550 and 1350-1400 A.D., precipitations were heavyin the Wakasa region, though there are no rising of sea-level, and dry and cool climate in China.
The Paleogene Hyuga Group of the Aradani Area in East Kyushu is regarded as an accretionary complex in the Shimanto Terrane. The Group was formerly inferred to form a melange including various sized blocks of sandstones, red and green siliceous mudstones, and basaltic volcanic rocks. The siliceous mudstones are not blocks in the melange, but occur as a low-angled thrust sheet of 40m thick. The Hyuga Group of the Aradani Area consists of four tectonic units;(1) lower chaotic unit, (2) siliceous mudstone unit, (3) mudstone unit, and (4) upper chaotic unit in ascending order. Each unit except for the siliceous mudstone unit forms a duplex structure, in which strata are imbricated, dipping 30° to 50° Each duplex is formed by mono-lithologic strata. The fundamental structure of the Paleogene Shimanto Terrane in Kyushu is characterized by low-angled nappe structures with stacked duplexes, in which duplexes lie one above the other, similarly to those of the Cretaceous Uchinohae Formation in South Kyushu. Original succession of the Hyuga Group is (1) basaltic volcanic rocks, (2) red and green siliceous mudstones of Middle Eocene, (3) black mudstones of Late Eocene, (4) sandstones and alternating beds of sandstone and mudstone of Late Eocene to Early Oligocene. Chaotic beds of melange facies originate from all above-mentioned strata. The siliceous mudstones, which are considered to be hemipelagic sediments, were subducted, and then formed a thrust sheet during underplating. The siliceous mudstones were probably situated in the decollement horizon, but did not flow as a lubricant layer.
A partial history of large earthquakes can be inferred from the stratigraphy, radiocarbon ages, fossil diatom assemblages, and FeS2-S contents of late Holocene intertidal sediments beneath South Slough, a narrow, protected arm of the Coos Bay estuary on the central Oregon coast. A total of 51 25-mm-diameter gouge cores collected to 2-7m depth showed sequences of interbedded peaty and muddy sediments beneath fringing marshes at ten small inlets around South Slough. Radiocarbon, diatom, and FeS2-S samples were obtained from two additional 70-mm-diameter cores at the Talbot Creek and Middle Creek sites. As many as nine peaty horizons, most interpreted to be former marsh soils, were encountered at some sites. Many of the buried soils have abrupt to sharp upper contacts with overlying mud suggesting that upper intertidal marsh soils were suddenly lowered into the lower part of the intertidal zone. In contrast, the gradual lower contacts of the peaty soils suggest gradual shoaling from a mud flat to the higher parts of a marsh. Repeated times of very rapid submergence inferred from the abrupt lithologic changes in the cores is supported by our interpretations of changes in diatom assemblages and FeS2-S contents in the two large-diameter cores. Peaty soils contain diatom assemblages of Group III, dominated by fresh to brackish species, whereas muddy sediments contain assemblages of Groups I (marine species) or II (brackish species). FeS2-S contents increase abruptly across the upper contact of peaty soils, also indicating a sudden change to a more strongly marine environment. Accelerator mass spectrometer radiocarbon dating indicates times of sudden submergence at about 0.4, 1.0, 1.3, 1.7, and 2.5ka. South Slough lies near the distal part of the active fold and thrust b elt of the North America plate, about 75km east of the inferred trace of the pl ate-bounday thrust of the Cascadia subduction zone. Pleistocene marine terraces near the slough record deformation on northwest-trending folds and flexure-slip and high-angle faults due to crustal shortening in the overriding North America plate. Thus, the repeated sudden submergence inferred from the sediments of the slough may record localized subsidence during shallow earthquakes on local structures in the overriding plate. However, given its distance arcward of the trace of the Cascadia thrust, South Slough may also fall within the western part of regional zones of coseismic subsidence during great plate-boundary earthquakes. If so, the interbedded peat and mud stratigraphy probably records a partial history of great subduction -zone earthquakes. Because many localized deformation events may be coincident with plate-boundary earthquakes, distinguishing local from regional coseismic subsidence is difficult at Sough Slough.
On January17, 1995, the earthquake of magnitude 7.2 occurred in the southern Hyogo Prefecture, Japan. The Nojima Earthquake Fault 17km long was formed from Ezaki lighthouse at the northeastern end of Awaji island to Ichinomiya-cho, which occurred along the Nojima geological fault in the northern segment and as a new fault in the southern segment. The northern segment of the Nojima Earthquake Fault is composed of some subparallel shear faults and a lot of echelon extension cracks, and the southern segment consists of some discontinuous surface ruptures. The Nojima Earthquake Fault shows a general trend striking N30°-60°E, dipping 75°-85°E. The topographical deformation and striations on the fault plane generated during seismic faulting show that the Nojima Earthquake Fault is a right-lateral strike-slip fault with some thrust component. The largest displacements are 180cm in horizontal, 130cm in vertical, and 215cm in netslip measured at the Nojima Hirbayashi fault scarp.
Distinctive ruptures of the surface faulting which generated the destructive 1995 Hyogoken-Nanbu Earthquake (Ms=7.2) appeared along the Nojima fault, an active fault on the northwestern coast of Awaji island, Japan. The surface fault ruptures in Awaji island extend southwestward continuously for about 9km from Easki near the epicenter to Toshima in Hokudan town, and caused prominent right-latearl off-sets of 1.9m at maximum on roads, paddy dikes with vertical displacement of 1.2m at maximum, while no large surface faulting has been reported in Kobe where major damage and casualties have appeared. Most of the surface ruptures follow along the pre-existing active fault traces of the Nojima fault. The ruptures are generally arranged in left-stepping echelon, and local extensional and compressional jog forms such as trenches, mole tracks, buldges are sometimes related to changes in fault strikes. The earthquake fault seems to have propagated bilaterally northeastward and southwestward from the hypocenter in the Straits of Akashi near the major jog of the earthquake fault system. The source process of the earthquake deduced from the slip distribution along the earthquake fault in Awaji island well explains near-field P-waveforms of broad-band seismometers for early part in about 4 seconds. The later part of much larger amplitude should attribute to the northeast fault ruptures toward Kobe.