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Multi‐scale Decomposition of Co‐seismic Deformation from High Resolution DEMs: a Case Study of the 2004 Mid‐Niigata Earthquake 总被引：1，自引：0，他引：1
Decomposing co-seismic deformation is an immediate need for researchers who are interested in earthquake inversion analysis and geo-hazard mapping. However, conventional InSAR or digital elevation models (DEMs) imagery analyses only provide the displacement in the Line-of-Sight (LOS) direction or elevation changes. The 2004 Mid-Niigata earthquake in Japan provides lessons on how to decompose co-seismic deformation from two sets of DEMs. If three adjacent points undergo a rigid-body-translation movement, their co-seismic deformation can be decomposed by solving simultaneous equations. Although this method has been successfully used to discuss tectonic deformations, the algorithm needed improvement and a more rigorous algorithm, including a new definition of nominal plane, DEMs comparability improvement and matrix condition check is provided. Even with these procedures, the obtained decomposed displacement often showed remarkable scatter prompting the use of the moving average method, which was used to determine both tectonic and localized displacement characteristics. A cut-off window and a pair of band-pass windows were selected according to the regional geology and construction activities to ease the tectonic and localized displacement calculations, respectively. The displacement field of the tectonic scale shows two major clusters of large lateral components, and coincidently major visible landslides were found mostly within them. The localized displacement helps to reveal hidden landslides in the target area. As far as the Kizawa hamlet is concerned, the obtained vectors show down-slope movements, which are consistent with the observed traces of dislocations that were found in the Kizawa tunnel and irrigation wells. The method proposed has great potential to be applied to understanding post-earthquake rehabilitation in other areas. 相似文献
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MARI OGAWA AKIRA TAKEUCHI MUTSUO HATTORI MASAHARU OKANO MISUMI AOKI MAKIKO IMAMURA TOYOKI KSUBOI TOMONORI TSUBOI DAISUKE TANIMOTO TAKESHI NAGANUMA 《Island Arc》2002,11(4):274-286
Abstract The manned submersible Shinkai 2000 investigated yellow patches on the near-summit slope of Shiribeshi Seamount in the Japan Sea. Yellowish patches are often associated with seepage, and the possibility of seepage at Shiribeshi Seamount was tested by the following four lines of observation: (i) high subsurface temperature was measured at a ring-like patch, although no increase in subsurface temperature was observed at other patches; (ii) high gamma ray (γ-ray) intensity from the thorium series was recorded in the patch zone; (iii) the yellowish deposit was composed of calcite, quartz and amorphous iron compound, as seen at the yellowish patches in other seeps and volcanoes; (iv) lipid phosphate, a measure of microbial abundance, in sediments of the ring-like patch was determined, and the recorded microbial abundance was higher inside the patch than outside it. The four lines of observation are explained consistently by postulating that the seepage of warm fluid contained Fe and γ-ray sources. A hydrothermal origin of the yellow patches is not ruled out for the extinct but young (0.9 Ma) arc volcano. 相似文献
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Pressure-Temperature Path Recorded in the Yangkou Garnet Peridotite, in Su-Lu Ultrahigh-pressure Metamorphic Belt, Eastern China 总被引：2，自引：0，他引：2
Chemical variations along with changes in microstructure ofthe principal constituent minerals make it possible to identifyat least four equilibrium stages in the evolution of the Yangkougarnet peridotite in the Su-Lu ultrahigh-pressure metamorphicbelt, eastern China: Stage I—a primary garnet lherzolitestage represented by coarse-grained (a few millimeters size)porphyroclastic aluminous pyroxenes + chromian spinel ±garnet; Stage II—an ultrahigh-pressure (UHP) stage definedby fine-grained matrix phases (0·1–0·3 mmsize) of garnet + extremely low-Al orthopyroxene + high-Na clinopyroxene+ chromite; Stage III—a medium-pressure stage definedby fine-grained mineral aggregates (<0·1–0·2mm size) mainly composed of aluminous spinel + high-Al orthopyroxenein the matrix; Stage IV—an amphibolite- to greenschist-faciesstage defined by poikiloblastic amphibole. Orthopyroxene–clinopyroxenethermometry and an empirical spinel barometer give temperaturesof around 800–830°C and pressures of 1·2–2·9GPa for porphyroclasts of Stage I. Garnet–orthopyroxene,garnet–clinopyroxene and empirical spinel geothermobarometersgive relatively uniform P–T conditions for the matrixgarnet–orthopyroxene–clinopyroxene–chromiteassemblage of Stage II ( 相似文献
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Abstract— The Mg‐isotopic compositions in five barred olivine (BO) chondrules, one coarse‐grained rim of a BO chondrule, a relic spinel in a BO chondrule, one skeletal olivine chondrule similar to BO chondrules in mineralogy and composition, and two non‐BO chondrules from the Allende meteorite have been measured by thermal ionization mass spectrometry. The Mg isotopes are not fractionated and are within terrestrial standard values (±2.0%o per amu) in seven of the eight analyzed ferromagnesian chondrules. A clump of relic spinel grain and its host BO chondrule R‐11 give well‐resolvable Mg fractionations that show an enrichment of the heavier isotopes, up to +2.5%‰ per amu. The Mg‐isotopic compositions of coarse‐grained rim are identical to those of the host chondrule with BO texture. The results imply that ferromagnesian and refractory precursor components of the Allende chondrule may have been formed from isotopically heterogeneous reservoirs. In the nebula region where Allende chondrules formed, recycling of chondrules and multiple high‐temperature heating did not significantly alter the chemical and isotopic memory of earlier generations. Chemical and isotopic characteristics of refractory precursors of carbonaceous chondrite chondrules and CAIs are more closely related than previously thought. One of the refractory chondrule precursors of CV Allende is enriched in the heavier Mg isotopes and different from those of more common ferromagnesian chondrule precursors. The most probable scenario at the location where chondrule R‐11 formed is as follows. Before chondrule formation, several high‐temperature events occurred and then RPMs, refractory oxides, and silicates condensed from the nebular gas in which Mg isotopes were fractionated. Then, this CAI was transported into the chondrule formation region and mixed with more common, ferromagnesian precursors with normal Mg isotopes, and formed the BO chondrule. Because Mg isotope heterogeneity among silicates and spinel are found in some CAIs (Esat and Taylor, 1984), we cannot rule out the possibility that Mg isotopes of a melted portion of the refractory precursor (i.e., outer portion of CAI) are normal or enriched in the light isotope. Magnesium isotopes in the R‐11 host are also enriched in the heavier isotopes, +2.5%o per amu, which suggests that effects of isotopic heterogeneity among silicates and spinel, if they existed, are not considered to be large. It is possible that CAI precursor silicates partially dissolved during the chondrule forming event, contributing Mg to the melt and producing a uniform Mg‐isotopic signature but enriched in the heavier Mg isotopes, +2.5%‰ per amu. Most Mg isotopes in more common ferromagnesian chondrules represent normal chondritic material. Chemical and Mg‐isotopic signatures formed during nebular fractionations were not destroyed during thermal processes that formed the chondrule, and these were partly preserved in relic phases. Recycling of Allende chondrules and multiple heating at high temperature did not significantly alter the chemical and Mg‐isotopic memory of earlier generations. 相似文献
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祁连山七一冰川物质平衡的最新观测结果 总被引：36，自引：16，他引：20
祁连山七一冰川观测结果表明, 2001/2002年度和 2002/2003 年度冰川物质平衡分别为-810mm和-316 mm水当量, 冰面出现显著的减薄状态. 和过去的观测结果相比较, 20 世纪 70 年代为较大的正平衡, 年平均为360 mm水当量; 80年代年平均为4 mm水当量, 基本接近零平衡状态. 到近两年亏损强烈, 为所有观测资料中负平衡值最大的年份, 零平衡线也达到最高位置. 物质平衡出现较大的负值和零平衡线位置升高的状况, 强烈反映了祁连山冰川对气候变暖过程的响应. 如果气候变暖趋势继续, 冰川物质平衡负值将增大、冰面减薄和雪线的升高, 冰川将继续呈现萎缩状态. 相似文献
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