Infrared polarization of venus: Its periodic fluctuations and evidence for thin haze

Infrared polarimetry of Venus over the phase angles from 18 to 171° has been made extending previous measurements (S. Sato, K. Kawara, Y. Kobayashi, H. Okuda, K. Noguchi, T. Mukai, and S. Mukai (1980). Icarus43, 288) in both wavelength λ and phase angle θ. The results of polarization measurements at 2.25 μm ? λ ? 5.0 μm are (i) small positive and negative values at K(2.25 μm), (ii) a remarkable variation with λ in the CVF(2.2?4.2μm) filter region, (iii) a nearly smooth curve as a function of θ having a peak value of ～36% at θ ～ 90° at both 3.6 μm and L′(3.8 μm), and (iv) a decrease with increasing field of view at M(5.0 μm) due to the contamination of thermal emission from the dark crescent. Furthermore, at 3.6 μm and L′(3.8 μm), (v) higher values at the poles than at the equator and (vi) 4.5- to 5.9-day periodic fluctuations are also found. From a comparison with model calculations, the results confirm the existence of a thin haze layer consisting of submicron-size particles above the main clouds of Venus; e.g., its optical thickness is about 0.1 at λ ～ 0.94 μm. In addition, result (vi) could be explained by a variation of the optical thickness of the haze layer or that of the brightness temperature of the main clouds.     

Horizontal and vertical components of earthquake ground motions at liquefiable sites

Field observations on ground motions from recent earthquakes imply that current knowledge is limited with regard to relating vertical and horizontal motions at liquefiable sites. This paper describes a study with the purpose of clarifying this emerging issue to some extent. A series of numerical analyses is carried out on a liquefiable soil deposit with a verified, fully coupled, nonlinear procedure. It is shown that the transformation of vertical motions in the deposit differs considerably from the transformation of horizontal motions. Both the amplitude and frequency content of the horizontal motions are strongly dependent on the shaking level or the associated nonlinear soil behavior. The transfer function for vertical motions is however likely to be independent of the intensity of input motions; no reduction in the amplitude occurs even in the case of strong shaking. The results are shown to be in consistence with the laboratory observations on shaking table tests and recent field observations that less nonlinearity exists for vertical motions. It is also shown that the possibility exists for using information on spectral ratios between the horizontal and vertical surface motions to quickly identify in situ soil behavior and liquefaction that are not readily covered by conventional field or laboratory experimentation procedures.     

A time-space based approach for mapping rainfall-induced shallow landslide hazard

A rainfall-induced shallow landslide is a major hazard in mountainous terrain, but a time-space based approach is still an unsettled issue for mapping rainfall-induced shallow landslide hazards. Rain induces a rise of the groundwater level and an increase in pore water pressure that results in slope failures. In this study, an integrated infinite slope analysis model has been developed to evaluate the influence of infiltration on surficial stability of slopes by the limit equilibrium method. Based on this new integrated infinite slope analysis model, a time-space based approach has been implemented to map the distributed landslide hazard in a GIS (Geographic Information Systems) and to evaluate the shallow slope failure induced by a particular rainfall event that accounts for the rainfall intensity and duration. The case study results in a comprehensive time-space landslide hazard map that illustrates the change of the safety factor and the depth of the wetting front over time.     

A computational procedure for joining separate map sheets

Map sheets have been often used as a basic spatial unit for managing spatial data produced from paper maps. This often results in incompatibility between adjacent map sheets, because spatial objects do not cross the boundaries smoothly and even the boundaries themselves do not match their neighbors exactly. To solve the problem this paper proposes a computational procedure for joining separate map sheets to obtain seamless spatial data. Line objects digitized separately in different map sheets are considered, which are frequently used to represent road networks, gas pipelines, and boundaries of polygon objects. The procedure consists of three steps: (1) extraction of end nodes, (2) detection of matching nodes, and (3) transformation of the map sheet. Each step goes interactively so that unexpected errors can be avoided by human observation. To test the validity of the procedure, map sheets are combined containing the road network data of Tokyo 23-ku area, Japan. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cation disorder in garnets along the Mg3Al2Si3O12-Mg4Si4O12 join: an infrared,Raman and NMR study

We have obtained infrared and Raman spectra for garnets synthesized at high (static) pressures and temperatures along the join Mg₃Al₂Si₃O₁₂ (pyrope) — Mg₄Si₄O₁₂ (magnesium majorite). The vibrational spectra of Mg-majorite show a large number of additional weak peaks compared with the spectra of cubic pyrope garnet, consistent with tetragonal symmetry for the MgSiO₃ garnet phase. The Raman bands for this phase show no evidence for line broadening, suggesting that Mg and Si are ordered on octahedral sites in the garnet. The bands for the intermediate garnet compositions are significantly broadened compared with the end-members pyrope and Mg-majorite, indicating cation disorder in the intermediate phases. Solid state ²⁷Al NMR spectroscopy for pyrope and two intermediate compositions show that Al is present only on octahedral sites, so the cation disorder is most likely confined to Mg-Al-Si mixing on the octahedral sites. We have also obtained a Raman spectrum for a natural, shock-produced (Fe,Mg) majorite garnet. The sharp Raman peaks suggest little or no cation disorder in this sample.     

满洲里-新巴尔虎右旗斑岩系列矿床石英流体包裹体液相组分的PIXE分析和地质应用

ＰＩＸＥ（质子感应Ｘ射线分析）方法是目前国际上新的流体包裹体成分分析方法。在前人工作的基础上,尝试用ＰＩＸＥ方法分析了满洲里－新巴尔虎右旗斑岩系列多金属矿床石英流体包裹体的液相多元素化学组分,其结果反映了地质矿化规律。该方法对于多金属矿床石英流体包裹体成分研究非常有用。结合其他包裹体研究,提出甲乌拉与直干布拉根矿床流体组分和成矿物理化学条件均不同,初步认为不存在同一矿化中心;还提出了查干布拉根矿床西矿段深部可能存在乌奴格吐山式斑岩型Ｃｕ矿床,应引起注意。     

Crustal structure of the continental margin of Korea in the East Sea (Japan Sea) from deep seismic sounding data: evidence for rifting affected by the hotter than normal mantle

Despite the various opening models of the southwestern part of the East Sea (Japan Sea) between the Korean Peninsula and the Japan Arc, the continental margin of the Korean Peninsula remains unknown in crustal structure. As a result, continental rifting and subsequent seafloor spreading processes to explain the opening of the East Sea have not been adequately addressed. We investigated crustal and sedimentary velocity structures across the Korean margin into the adjacent Ulleung Basin from multichannel seismic (MCS) reflection and ocean bottom seismometer (OBS) data. The Ulleung Basin shows crustal velocity structure typical of oceanic although its crustal thickness of about 10 km is greater than normal. The continental margin documents rapid transition from continental to oceanic crust, exhibiting a remarkable decrease in crustal thickness accompanied by shallowing of Moho over a distance of about 50 km. The crustal model of the margin is characterized by a high-velocity (up to 7.4 km/s) lower crustal (HVLC) layer that is thicker than 10 km under the slope base and pinches out seawards. The HVLC layer is interpreted as magmatic underplating emplaced during continental rifting in response to high upper mantle temperature. The acoustic basement of the slope base shows an igneous stratigraphy developed by massive volcanic eruption. These features suggest that the evolution of the Korean margin can be explained by the processes occurring at volcanic rifted margins. Global earthquake tomography supports our interpretation by defining the abnormally hot upper mantle across the Korean margin and in the Ulleung Basin.