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941.
通过精细的地震资料解释,在塔里木盆地中部的满西地区发现晚志留世-石炭纪伸展构造。伸展构造由一系列规模不大的正断层组成,平面上组成两条北东-南西向的左行雁列状正断层带,剖面上构成负花状构造和堑垒构造。根据生长系数计算结果,正断层形成于晚志留世,在泥盆纪和石炭纪持续活动,于石炭纪末停止活动。正断层活动的高峰期为晚志留世。该期伸展构造在塔中和塔北地区也有发育,反映当时塔里木盆地处于区域性伸展构造背景。塔里木盆地晚志留世-石炭纪的伸展构造,是昆仑早古生代晚期(晚奥陶世-中志留世)碰撞造山后构造应力松弛作用的产物。 相似文献
942.
2013年12月16日三峡库区巴东发生Ms5.1地震.根据eigen-6c2模型研究了巴东地区的8-638阶卫星重力异常, 结果表明: 该地区场源深度为10 km的地壳为局部重力低异常, 反映了该处物质密度较周围偏低, 形成低密度层.同时, 研究了该地区速度结构剖面, 结果表明: 巴东地区地壳5~9 km及10~15 km深处存在上下两个低速层, 上部低速层与水库渗水有关, 下部低速层与地幔热流体的上涌有关.低密度层和低速层的确定为韧性流变层的存在提供了证据.巴东地震是地壳深部能量的长期集聚与突发释放, 属构造地震.然而, 库水下渗引起的上部低速异常降低了断层活动的阈值, 震前库水载荷的变化对此次巴东地震的发生起到了触发作用.通过对比次声波和地震波, 我们得出次声波仪记录到的异常信号为本地次声波. 相似文献
943.
944.
Wu Qu Michael Vicent Shija Jie Wu Min Jin Jianxin Wang Runying Zeng Zhuhua Chan 《海洋学报(英文版)》2022,41(8):120-128
The prokaryotic microbial communities in the sediments play crucial roles in the ecological functions of mangrove ecosystems. Therefore, the environmental factors that affect the structures of these prokaryotic microbial communities could indirectly participate in the regulation of mangrove functions, which is of great value for mangrove studies. The particle size (PS) of soils is recently demonstrated as a key environmental factor for shaping the microbial communities; however, this hypothesis has rarely been tested for mangrove environments. A case study of three tropical mangroves from Sanya, China was performed in this work to assess the influence of PS on the prokaryotic microbial community structures of bacteria, archaea, diazotrophs, and denitrifiers in the sediments. Results showed the variability in the spatial scale and the stability in the temporal scale for the prokaryotic communities, indicating that the tropical mangrove sediments could be a versatile but stable environment. Among the collected environmental factors, PS, salinity, and humidity had the greatest impacts, and PS mostly affected the structures of these prokaryotic communities based on its highest R2 values of canonical correspondence analysis, Mental test, and linear fitting (p≤0.05). Furthermore, PS was positively correlated with the diversity and abundance of diazotrophic communities and negatively correlated with the abundances of methanogenic communities including Methanobacteriaceae, Methanospirillaceae, Methanoregulaceae, and Methanosaetaceae. Former studies show the increasing trend of PS caused by the rise of sea level and the intensification of human activities. Therefore, our findings indicate that PS could be a potential intermediate that links climate change and human activities with the possible ecological function migration of mangroves; meanwhile, the increase of PS could in turn release the stress of these environmental changes by increasing the abundance and diversity of the diazotrophic community and decreasing the abundances of methanogens. 相似文献
946.
在利用三江源地区及邻近区域探空资料对NCEP/NCAR I再分析资料进行适用性分析的基础上,采用1971—2010年再分析资料的逐日风场和比湿数据,分析三江源地区水汽输送的变化。结果表明:1971—2010年,经向流入三江源地区的水汽显著减少,使区域总水汽收支也呈显著减少趋势。水汽通量在1970年代和1980年代的变化相对较小,在1990年代和2000年代的变化幅度则较大。三江源地区总水汽收支在春季、夏季和秋季均呈明显减少趋势,冬季则无明显变化。三江源地区水汽输入明显减少,特别是6月和9月显著减少,对该地区降水形成不利。 相似文献
947.
Holocene lake level variations on the Qinghai-Tibetan Plateau 总被引:1,自引:0,他引:1
Xiang-Jun Liu Zhong-Ping Lai Fang-Ming Zeng David B. Madsen Chong-Yi E 《International Journal of Earth Sciences》2013,102(7):2007-2016
Paleoshorelines indicative of multiple high lake stages can be found around many lakes on the Qinghai-Tibetan Plateau (QTP). Conspicuous paleoshorelines associated with the most recent highstands can be readily observed on satellite images and during field investigations. However, earlier paleoshorelines have been identified at only a few sites around these lakes due to a lack of clear shoreline features and limited spatial extension of those that can be identified. We investigated past lake highstands using published chronologies, Aster-DEM, Google Earth, and ArcGIS 9.2 software. These data suggest that (1) paleoshorelines of the most recent lake highstand were formed during the Holocene; (2) during this highstand, lake levels reached more than 90, 60–90, and 30–60 m higher than present in the central Gangdise and western Qiangtang areas, while in the eastern Qiangtang, Holxil-Yushu, and northeastern QTP areas highstands did not exceed 30 m above modern; (3) during the early Holocene, some lakes on the southwestern QTP combined to form large lakes, while lakes in the inland areas of the QTP were only a little larger during the Holocene high lake level stages. 相似文献
948.
Soil moisture and its variations are key factors for understanding hydrological processes, which are characterized by a high temporal variability at different scales. The study was conducted at three field stations in the desert regions of northwestern China, where soil moisture measurements with gravimetric method were used to characterize the temporal stability of soil moisture using various statistical parameters and an index of temporal stability (ITS). The soils are a gray–brown desert soil at the Linze station, an aeolian sandy soil at the Fukang station, and a brown desert soil at the Cele station. Soil textures are accordingly sandy loam at Linze and Cele, and loamy sand at Fukang. The dynamic variation in soil moisture depends strongly on the rainfall pattern (amount and frequency) in these desert ecosystems. Soil moisture content is low and significantly different among the three desert ecosystems, with the maximum at the Linze station (6.61 ± 2.08 %), followed by the Cele (4.83 ± 0.81 %) and Fukang (3.46 ± 0.47 %) stations. The temporal pattern exhibits high variability because soil moisture is characterized by low temporal stability and a high coefficient of variation (CV). The standard deviation, CV, and ITS increase significantly with increasing soil moisture. Soil moisture displays a skewed frequency distribution that follows a logarithmic function at lower soil moisture but a log-normal distribution at higher values. 相似文献
949.
950.