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991.
992.
Formation and shortening deformation of a back-arc rift basin revealed by deep seismic profiling, central Japan 总被引:1,自引:0,他引:1
Hiroshi Sato Takaya Iwasaki Shinji Kawasaki Yasutaka Ikeda Nobuhisa Matsuta Tetsuya Takeda Naoshi Hirata Taku Kawanaka 《Tectonophysics》2004,388(1-4):47
The northern Fossa Magna (NFM) basin is a Miocene rift system produced in the final stages of the opening of the Sea of Japan. It divides the major structure of Japan into two regions, with north-trending geological structures to the NE of the basin and EW trending structures to the west of the basin. The Itoigawa-Shizuoka Tectonic Line (ISTL) bounds the western part of the northern Fossa Magna and forms an active fault system that displays one of the largest slip rates (4–9 mm/year) in the Japanese islands. Deep seismic reflection and refraction/wide-angle reflection profiling were undertaken in 2002 across the northern part of ISTL in order to delineate structures in the crust, and the deep geometry of the active fault systems. The seismic images are interpreted based on the pattern of reflectors, the surface geology and velocities derived from refraction analysis. The 68-km-long seismic section suggests that the Miocene NFM basin was formed by an east dipping normal fault with a shallow flat segment to 6 km depth and a deeper ramp penetrating to 15 km depth. This low-angle normal fault originated as a comparatively shallow brittle/ductile detachment in a high thermal regime present in the Miocene. The NFM basin was filled by a thick (>6 km) accumulation of sediments. Shortening since the late Neogene is accommodated along NS to NE–SE trending thrust faults that previously accommodated extension and produce fault-related folds on their hanging wall. Based on our balanced geologic cross-section, the total amount of Miocene extension is ca. 42 km and the total amount of late Neogene to Quaternary shortening is ca. 23 km. 相似文献
993.
Zoltn Hajnal Endre Hegeds G. Randy Keller Tams Fancsik Attila Cs. Kovcs Rbert Csabafi 《Tectonophysics》2004,388(1-4):239
A specially designed 700-km2 grid survey, deploying 1000 regularly distributed low-frequency seismic recording systems, successfully investigated one of the most complex geologic environments of the Pannonian basin. The wide-angle signals penetrated through over 1000 m of multi-phase igneous lithology and recognized, for the first time, the underlying enigmatic Permian to Early Triassic basement rocks. Tomographic inversion of the first arrival grid data resulted in determination of an accurate three-dimensional (3-D) velocity field, to a depth of 4 km. The anomalous changes of the spatial velocity data outline the regional extent of the Late Miocene magmatic intrusions, which are covered by over 2000 m of Mid-Miocene to Pleistocene clastics. Complex relationship was found between the surface potential data and the intrusive bodies. This multi-faceted geophysical data analysis established a functional technique for mapping a subsurface with intricate acoustic and structural complexity. 相似文献
994.
于3个假说和林冠上方2m处的气象变量,采用Penman-Monteith组合模型估算了一个生长季节内川西亚高山林区分别以云杉(SF)、冷杉(FF)和白桦(BF)为优势树种的3个林分的湿林冠蒸发速率(Er)。研究结果表明,SF、FF和BF的湿林冠蒸发量(E)分别为44.51mm、88.51mm和57.8mm,分别占总降雨量的9.2%、16.6%和10.2%。与SF和BF相比,FF具有最高的月平均Er和蒸发比例。SF、FF和BF的平均Er分别为0.097mm/h(变化范围:0.028-0.487mm/h)、0.242mm/h(变化范围:0.068~0.711mm/h)和0.149mm/h(0.060~0.576mm/h)。最高和最低的月平均Er分别在6月(SF、FF和BF分别为0.120mm/h、0.317mm/h和0.169mm/h)和10月(SF、FF和BF分别为0.083mm/h、0.187mm/h和0.101mm/h)。8:00至16:00期间的平均点Er显著高于0:00至8:00以及16:00至0:00期间的平均Er。Er显著的日变化和月变化主要归因于林冠上方的太阳辐射、空气温度和相对湿度的变化。 相似文献
995.
洛川黄土剖面中矿物固定态铵的分布 总被引:1,自引:2,他引:1
对洛川黄土中的固定铵进行了初步分析。结果表明,在所测定的黄土古土壤层中,固定铵态氮含量在130-1之间变化。黄土中的固定铵态氮含量明显低于古土壤。13万a以来洛川黄土剖面中固定铵的分布呈~210现三次大的低高值的振荡特征,即末次间冰期S1古土壤中固定铵态氮含量最高,其次为冰后期的S0古土壤层,末次冰期形成的马兰黄土中固定铵态氮含量最低;在马兰黄土中同样体现出三次小的低高值的波动特征。黄土与μm组分的分布具有相似性,这些特征反映了洛川黄土中固定铵态氮的含量变化与气互层的古土壤中固定态铵的分布与黄土高原区气候的冷暖变化有较好的一致性,并且13万a以来洛川黄土剖面中固定铵的分布与磁化率和<2候条件有紧密的联系,揭示了黄土中固定铵的变化在一定程度上能指示黄土高原区古气候的演变。 相似文献
996.
Aggregate is a low unit-value mineral commodity. Costs to move aggregate from the mine site to the point of use is a large fraction of the resource cost to users. Production sites for aggregate occur where suitable source materials exist and where transportation and market conditions are favorable. The increasing demand for aggregate and the difficulty of developing and permitting new sites and of renewal of permits on existing sites of aggregate production indicates that aggregate will be supplied from sources yet to be developed or delineated in many areas. Site development and permitting for aggregate production is difficult because many land management plans and zoning actions fail to anticipate prospective source areas for aggregate in a way that is consistent with both the source rock quality and the transportation and socioeconomic factors that define the economic viability of the industry. Spatial analysis provides a method to integrate both geology and economic (transportation and marketplace) parameters in a regional model. Weights of evidence (WofE) analysis has been used to measure the spatial correlation of geologic map, transportation network, and population data with current production sites for crushed stone aggregate in the New England region of the northeastern United States. Weighted logistic regression (WLR) is used with the WofE results to rank areas in terms of their relative suitability for production of crushed stone. Spatial analysis indicates that 85% of the 106 crushed stone aggregate quarries in New England are sited within 1.6 km (1 mile) of either a principal highway or rail line in the region. Seventy-eight percent of crushed stone aggregate quarries are sited in census tracts with population densities exceeding 100 people/mile2. These relations illustrate the importance of proximity to both transportation corridors and developing areas where aggregate is predominately used. Only one active crushed stone quarry is located in a census tract with a population density less than 15 people/mile2, reflecting the lack of sufficient market demand in many rural areas to develop an operation there. However, since 1990, almost all new quarries have been developed in census tracts with population densities less than 200 people/mile2, indicating the difficulty of permitting new quarry sites in highly populated areas. Crushed stone aggregate is produced predominately from three hard rock types that are distributed widely in New England; 28% of sites use granitic rock, 25% use carbonate rocks, and 25% use mafic rock types that are categorized as trap rock by the aggregate industry. The other crushed stone aggregate sources include a variety of fine-grained metamorphic rock types. Carbonate rocks and Jurassic basalt (the primary trap rock source) are the most prevalent source rocks on an area-weighted basis. Spatial analysis can be used on a regional scale to rank areas by their relative suitabilityfor crushed stone aggregate production based on geology, transportation, and population parameters. The results of this regional analysis can identify areas for more detailed evaluation. As transportation or population features change, the model can be revised easily to reflect these changes. 相似文献
997.
998.
介绍了基于代理Servlet的移动定位服务系统AMLS的系统架构,重点讨论了空间对象的高效查询和解析、移动用户GPS位置的获取和代理Servlet等关键技术的实现方法,并对AMLS进行了具体的实践。 相似文献
999.
1000.