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31.
Two piston cores, one located far from the continents (The North Pacific Ocean: ES core), and another located comparatively closer to the continents (The Bering Sea: BOW-8a core) were investigated to reconstruct environmental changes on source land areas. The results show significant contribution of terrestrial organic matter to sediments in both cores. The δ13C values of n-C27, n-C29, and n-C31 alkanes in sediments from the North Pacific ES core show significant glacial to interglacial variation whereas those from the Bering Sea core do not. Variations of δ13C values of land plant n-alkanes are related to the environmental or vegetational changes in the source land areas. Environmental changes, especially, aridity, rainfall, and pCO2 during glacial/interglacial transitional periods can affect vegetation, and therefore C3 / C4 plant ratios, resulting in δ13C changes in the preserved land plant biomarkers. Maximum values of δ13C as well as maximum average chain length values of long chain n-alkanes in the ES core occur mostly at the interglacial to glacial transition zones reflecting a time lag related to incorporation of living organic matter into soil and transportation into ocean basins via wind and/or ability of C4 plants to adapt for a longer period before being replaced by C3 plants when subjected to gradual climatic changes. Irregular variations with no clear glacial to interglacial trends in the BOW-8a core may result from complex mixture of aerosols from westerly winds and riverine organic matter from the Bering Sea catchments. In addition, terrestrial organic matter entering the Bering Sea could originate from multiple pathways including eolian, riverine, and ice rafted debris, and possibly be disturbed by turbidity and other local currents which can induce re-suspension and re-sedimentation causing an obliterated time relation in the Bering Sea biomarker records. 相似文献
32.
33.
This study estimated the trends in the number of days that fall within the near-zero (0?°C) range of the temperature continuum. This narrow range has importance for potential transportation hazards and freeze-thaw cycles. While the tails of the air-temperature distribution and their trends often are closely examined under the climate change context, the frequency and trend of other portions of the air-temperature distribution can be equally important, as many societal impacts are caused by events in the non-tail region, such as near-zero °C temperatures (NZT). Examining the trend of the number of NZT days over the conterminous USA for the period of 1948–1949 through 2010–2011, we found three distinct spatial clusters. The most distinctive spatial clusters are found along the West Coast (positive temperature trends leading to a decrease in NZT days), the High Plains and Northern Rockies (positive temperature trends leading to an increase in NZT days), and the southeastern USA (negative temperature trends leading to an increase in NZT days). While trends in the number of NZT days are linked to changes in mean minimum air temperature, increasing minimum temperature leads to a positive trend at NZT days only at some locations. 相似文献
34.
Reconnaissance report on landslide disasters in northeast Japan following the M 9 T��hoku earthquake
Toyohiko Miyagi Daisuke Higaki Hiroshi Yagi Shoji Doshida Noriyuki Chiba Jun Umemura Go Satoh 《Landslides》2011,8(3):339-342
An earthquake of Mw 9.0 struck the Pacific coast in northeast Japan on March 11, 2011 and was followed by a hugely damaging tsunami along 500 km
of the Japanese coastline. An inland aftershock of M. 7.0 occurred on April 11; during which, surface fault ruptures appeared
on land. A large variety of landslide disasters resulted from these earthquakes in various parts of northeastern Honshu, Japan.
The full extent of the landslides is still being determined. This brief report introduces some of the landslide phenomena
so far investigated by the Japanese Landslide Society. These are (1) failure of a water reservoir embankment dam in Sukagawa,
Fukushima prefecture, (2) landslides and surface seismic fault rupture from the April 11 aftershock in Iwaki, Fukushima, (3)
a concentration of surface failures at Matsushima Bay in Miyagi prefecture, and (4) small landslides on modified slopes in
residential areas around Sendai city. 相似文献
35.
Ichiro Kawasaki 《Geophysical Journal International》1982,71(2):395-424
Summary. A novel method is proposed for retrieving the 3-D orientation of axes of symmetry of near-source anisotropy by a non-linear inversion of observed radiation patterns of seismic displacement spectra of Rayleigh waves.
If faulting is generated within an anisotropic source region, body force equivalents for the faulting are in general not a double couple but the sum of three orthogonal dipole forces (Kosevich; Kawasaki & Tanimoto). As a result of the third dipole force, radiation patterns of Rayleigh waves are deformed, the deformation amounting to several per cent of those for an isotropic source medium. The non-linear inversion is carried out to find the optimum fault plane solutions giving the minimum square residual between observed and theoretical radiation patterns in some period range. In order to remove effects of heterogeneity along propagation paths, a pair-event scheme is involved in the inversion, which denotes taking spectral amplitude ratios and differential phases of the seismic displacement spectra of the pair-events having close hypocentres and different fault plane solutions. The uniqueness of the fault plane solutions of the non-linear inversion is afforded a proof by the Monte-Carlo experiment.
The non-linear inversion is repeated for some possible types of symmetry of the near-source orthotropic anisotropy due to the preferred orientation of olivine crystals as mantle materials. Square residuals thus obtained are compared with each other to see which orientation gives the minimum.
The method is applied to pair-events which occurred in the anomalous mantle beneath the Mid-Atlantic Ridge. This leads to a discovery that one type of symmetry of the preferred orientations with a -, b - and c-axes aligned vertical, parallel to and perpendicular to the trend (N11E) of the ridge axis, respectively, is most likely existing in the anomalous mantle. 相似文献
If faulting is generated within an anisotropic source region, body force equivalents for the faulting are in general not a double couple but the sum of three orthogonal dipole forces (Kosevich; Kawasaki & Tanimoto). As a result of the third dipole force, radiation patterns of Rayleigh waves are deformed, the deformation amounting to several per cent of those for an isotropic source medium. The non-linear inversion is carried out to find the optimum fault plane solutions giving the minimum square residual between observed and theoretical radiation patterns in some period range. In order to remove effects of heterogeneity along propagation paths, a pair-event scheme is involved in the inversion, which denotes taking spectral amplitude ratios and differential phases of the seismic displacement spectra of the pair-events having close hypocentres and different fault plane solutions. The uniqueness of the fault plane solutions of the non-linear inversion is afforded a proof by the Monte-Carlo experiment.
The non-linear inversion is repeated for some possible types of symmetry of the near-source orthotropic anisotropy due to the preferred orientation of olivine crystals as mantle materials. Square residuals thus obtained are compared with each other to see which orientation gives the minimum.
The method is applied to pair-events which occurred in the anomalous mantle beneath the Mid-Atlantic Ridge. This leads to a discovery that one type of symmetry of the preferred orientations with a -, b - and c-axes aligned vertical, parallel to and perpendicular to the trend (N11E) of the ridge axis, respectively, is most likely existing in the anomalous mantle. 相似文献
36.
John Menzies Michael Feast Patricia Whitelock Enrico Olivier Noriyuki Matsunaga Gary Da Costa 《Monthly notices of the Royal Astronomical Society》2008,385(2):1045-1052
JHK s near-infrared photometry of stars in the Phoenix dwarf galaxy is presented and discussed. Combining these data with the optical photometry of Massey et al. allows a rather clean separation of field stars from Phoenix members. The discovery of a Mira variable ( P = 425 d), which is almost certainly a carbon star, leads to an estimate of the distance modulus of 23.10 ± 0.18 that is consistent with other estimates and indicates the existence of a significant population of age ∼2 Gyr. The two carbon stars of Da Costa have M bol =−3.8 and are consistent with belonging to a population of similar age; some other possible members of such a population are identified. A Da Costa non-carbon star is Δ K s ∼ 0.3 mag brighter than these two carbon stars. It may be an asymptotic giant branch star of the dominant old population. The nature of other stars lying close to it in the K s , ( J − K s ) diagram needs studying. 相似文献
37.
Rain‐induced deep‐seated catastrophic rockslides controlled by a thrust fault and river incision in an accretionary complex in the Shimanto Belt,Japan
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To clarify the geological causes of rockslides induced by rainstorms in accretionary complexes, the geology and geomorphology of two large rockslides (volumes > 106 m3) induced by the heavy rainfall of Typhoon Talas in the Shimanto Belt, Kii Mountains, Japan in 2011 are investigated. Our analysis reveals that thrusts with brittle crush zones controlled the occurrence of the rockslides. The properties and distribution of thrusts were poorly constrained before this study. Flooding during the rainstorm removed surface materials along rivers, allowing thorough geological mapping to be performed. Gravitationally deformed slopes were studied using GIS analysis of 1 m digital elevation models (DEMs) and fieldwork, and X‐ray diffraction (XRD) analysis, permeability, and direct shear tests were used to characterize the mineralogy and geotechnical properties of fault gouge. The Kawarabi thrust has a brittle crush zone up to 6 m thick and acts as the sliding surface for both landslides. The thrust dips 34° downslope and is cut by high‐angle faults and joints along one or both sides of each landslide body. Prior to failure, the upper part of the slope contained small scarps, suggesting that the slopes were already gravitationally deformed. The slope instability can be attributed to long‐term river erosion, which has undercut the slope and exposed the thrust at the base of the slope. The groundwater level, monitored in boreholes, suggests that the Kawarabi thrust is a barrier to groundwater flow. The weak and impermeable nature of the thrust played an essential role in the generation of gravitational slope deformation and catastrophic failure during periods of increased rainfall. Thrusts are a common feature of accretionary complexes, including in the Shimanto Belt, and the mechanism of slope failure stated above can be typical of rockslides in accretionary complexes and provide new insights into landslide disaster mitigation. 相似文献
38.
Katsuyuki Sasaki Tsuneo Ono Katsuhisa Tanaka Kiyoshi Kawasaki Hiroshi Saito 《Journal of Oceanography》1998,54(5):593-603
Partial pressure of CO2 in surface sea water (pCO2) was measured continuously off Sanriku in May, 1997 by a new pCO2 measurement system. We have examined the relation of pCO2 to physical factors such as temperature, salinity and density, chemical and biological factors such as nutrients and carbonate
system and chlorophylla. In the Kuroshio region pCO2 was not correlated to physical, chemical and biological factors in the range of 260 to 290 μatom. In transition water (Tr1)
between Kuroshio and the Oyashio second branch, pCO2 was weakly correlated to physical factors and strongly correlated to nutrients. In transition water (Tr2) between the Oyashio
first and second branches, pCO2 was highly correlated to temperature (SD: 10.9 μatom) and salinity (SD: 8.6 μatom) and also to nutrients. In transition water
(Tr1+Tr2), pCO2 was highly multivariately correlated to temperature (T), salinity (S), chlorophylla (CH) (or nitrate+nitrite (N)) as follows, pCO2(μatom)= 10.8×T(°C)+27.7×S+2.57CH(μg/1) −769, R2= 0.86, SD = 20.9, or pCO2(μatom)= 3.9×T(°C)+25.5×S+16.0NO3(μM) −686, R2= 0.99, SD = 6.4. Moreover, pCO2 was predicted by only two factors, one physical (S) and the other chemical/biological (N) as follows: pCO2 (μatom)=32.8×S+19.4N−908, R2=0.97, SD=8.4. The pH measured at 25°C was well correlated with normalized pCO2 at a fixed temperature. In the Oyashio region pCO2 was decreased to 160 μatom, probably because of spring bloom, but was not correlated linearly to chlorophylla. The results obtained showed the possibility of estimating pCO2 of the Oyashio and transition regions in May by satellite remote sensing of SST, but the problem of estimation of pCO2 in Kuroshio water remains to be solved. 相似文献
39.
We investigated the structure and persistency of the dominant sea-surface temperature (SST) anomaly pattern in summer over
the North Pacific from 1960 to 2004, which has been attracting less attention than those in winter. The leading empirical
orthogonal functions (EOFs) for August and September, which can be treated as the summer patterns, rather resemble each other
in both spatial structure and time variations but are quite different from those of the other months. A lag correlation analysis
indicates that the summer patterns do not show significant persistency in the following winter and the summer of the next
year. An inappropriate definition of the summer season might obscure the characteristics of the dominant summer SST anomaly
pattern in the North Pacific. 相似文献
40.
Recent studies suggest that the destruction of methane by Cl in the marine boundary layer could be accounted for as another major sink besides the methane destruction by OH. High level ab initio molecular orbital calculations have been carried out to study the CH4+Cl reaction, the carbon Kinetic Isotope Effect (KIE) is calculated using Conventional Transition-State Theory (CTST) plus Wigner and Eckart semiclassical tunneling corrections. The calculated KIE is around 1.026 at 300 K and has a small temperature variation. This is by far the largest KIE among different processes involving atmospheric methane destruction (e.g., OH, soil). A calculated mass balance of atmospheric methane including the KIE for the CH4+Cl reaction is found to favor those methane budgets with enhanced biological methane sources, which have relatively lighter carbon isotope composition. 相似文献