桑沟湾不同形态锰的分布、季节变化及影响因素     

刘家琦  任景玲  陈晶  房瑞雪  蒋增杰 《海洋学报》2021,43(2):16-27

利用催化动力学分光光度法和两步提取法对2011年4月（春）、8月（夏）、10月（秋）和2012年1月（冬）桑沟湾海域溶解态无机锰(DIMn)和表层沉积物中的锰的含量进行测定。结果表明,桑沟湾4个季节（春季至冬季,后同）DIMn浓度呈现出近岸高、远岸低的分布特点,其平均浓度分别为(60.5±43.1) nmol/L、(42.0±30.5) nmol/L、(23.4±11.2) nmol/L和(18.2±13.5) nmol/L,呈现出明显的季节变化,即春季最高,夏季、秋季次之,冬季最低;与相邻的俚岛湾和爱莲湾相比,桑沟湾春季、夏季DIMn的浓度较高,秋季、冬季则没有显著性差异。桑沟湾表层沉积物中总Mn在4个季节的含量分别为(861±308) mg/kg、(915±322) mg/kg、(589±108) mg/kg、(653±185) mg/kg,表层沉积物中醋酸提取态Mn在4个季节的含量分别为(500±272) mg/kg、(502±232) mg/kg、(322±81) mg/kg、(345±91) mg/kg,两者均表现出近岸高、远岸低的分布特点。醋酸提取态Mn的含量在春季、夏季要显著高于秋季、冬季。悬浮颗粒物的吸附和浮游生物的利用是影响桑沟湾DIMn浓度与分布的重要因素。桑沟湾DIMn的源主要包括河流及地下水输送、大气输送、沉积物?水界面释放;汇主要包括养殖生物的清除、向黄海的输送等。简单箱式模型收支计算结果显示,桑沟湾DIMn的源略大于汇,表明除了养殖生物的清除和向黄海的输送,桑沟湾DIMn还存在其他汇。本研究的结果为桑沟湾DIMn的生物地球化学循环的深入认识提供了基础数据。  相似文献   

Vertical variations and composition of dissolved free amino acid in the seawater of the Yap Trench in the western Pacific Ocean     

Niu  Jiaohong  Sun  Chengjun  Yang  Bo  Xie  Lei  Jiang  Fenghua  Cao  Wei  Chen  Yan  Ding  Haibing  Huang  Yuhuan  Gao  Xianchi 《中国海洋湖沼学报》2023,41(1):118-137

The composition and concentration of dissolved free amino acid (DFAA) of seawater samples collected in May 2016 from the surface to the hadal zone of the northern region of the Yap Trench were analyzed by pre-column derivatization of o-phthalaldehyde. Results show that the average concentration of DFAA in the study area was 0.47±0.36 µmol/L. In different sampling stations, the concentrations of DFAA with water depth showed complex variation patterns. At the sediment-seawater interface, the concentrations of DFAA in the western side of the trench were obviously higher than that in its eastern side. In the study area, there were no significant correlations between the concentrations of DFAA and the environmental parameters such as concentrations of chlorophyll a (Chl a), dissolved oxygen (DO), pH, and dissolved inorganic nitrogen (DIN), indicating that the concentrations of DFAA in seawater of the trench are affected by many factors, such as photosynthesis, respiration, temperature, pressure, illumination, and circulation. The dominant DFAA are similar in different water layers of sampling stations, including aspartic acid (Asp), glutamic acid (Glu), glycine (Gly), and serine (Ser). The composition of different amino acids, and the relative abundance of acidic, basic, and neutral amino acids might be related to the sources and consumption of various amino acids. Nine pairs of amino acids in the DFAA showed significantly positive relationship by correlation matrix analysis, suggesting that they might share similar biogeochemical processes. The degradation index (DI) of the DFAA in seawater of the Yap Trench could reflect the degradation, source, and freshness of DFAA in the trench to some extents. This is a preliminary study of amino acids from sea surface to hadal zone in the ocean, more works shall be done in different trenches to reveal their biogeochemical characteristics in extreme marine environments.

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The NE Directed Seismicity Belt in Tibet after the MS8.1 Nepal Earthquake and Its Predictive Significance     

Wang Shuangxu  Zhu Liangyu  Xu Jing  Ji Lingyun  Jiang Fengyun 《中国地震研究》2018,32(1):119-129

After the 2015 M_S8.1 Nepal earthquake, a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper, we attempt to summarize the features and investigate the primary mechanism of this behavior of seismic activity, using a 2-D finite element numerical model with tectonic dynamic settings and GPS horizontal displacements as the constraints. In addition, compared with the NE-trending seismicity belt triggered by the 1996 Xiatongmoin earthquake, we discuss the future earthquake hazard in and around Tibet. Our results show that:the NE-directed seismicity belt is the response of enhanced loading on the anisotropic Qinghai-Tibetan plateau from the Indian plate and earthquake thrusting. Also, this possibly implies that a forthcoming strong earthquake may fill in the gaps in the NE-directed seismicity belt or enhance the seismic hazard in the eastern (the north-south seismic zone) and western (Tianshan tectonic region) parts near the NE-directed belt.  相似文献   

地震作用下低层建筑砌体结构的动力特性分析          下载免费PDF全文

雷江 《地震工程学报》2018,40(3):432-437

传统低层建筑砌体结构动力特性分析中,易受到外界环境的干扰,砌体结构的完整性欠缺,导致动力特性分析的准确度较低。为提高低层建筑砌体结构的抗震性能,提出地震作用下低层建筑砌体结构的动力特性分析方法。首先利用低层建筑砌体结构反应自功率谱,完成砌体结构的自振频率辨认;然后通过941B型超低频率测振仪测试自振频率,筛出振动波形中噪声干扰的区域,获取时域波形和频域波形;最后依据时域波形和频域波形塑造低层建筑砌体三维精细化模型,在该模型基础上,通过子空间迭代算法获取低层建筑砌体结构的模拟结果,分析地震作用下芯柱、圈梁等构造措施对建筑砌体结构动力特征的影响,完成砌体结构的动力特性分析。实验结果表明,利用所提方法对地震作用下低层建筑砌体结构的动力特性进行分析,得到的分析结果准确度较高。  相似文献   

地震计线性误差精确测试     

王洪体  崔仁胜  李江  叶鹏  林湛 《地震地磁观测与研究》2018,39(2):173-177

利用同步测试标准地震数据采集器标定电流的地震计线性误差测试方法,避免了标定信号输出电流波动对地震计线性误差测试的影响,按DB/T 21—2007规定的方法进行数据处理,并判定结果是否符合DB/T 22—2007的要求。实际测试表明,该方法测试精度可以达到0.000 5%,满足测试线性偏差小于0.01%的需要,且操作简单,无额外设备要求,可行性高,可在固定地震台站、野外等条件下使用,具有较大的应用价值。  相似文献   

以颗粒物理原理认识汶川M_W 7.9地震发生前临震预滑和震颤现象     

许健生  黄辅琼  李丽  姜振海  冯红武  董立杰 《地震地磁观测与研究》2018,40(1):21-35

发生在孕震区周边地块上的临震预滑和震颤现象,对破坏性地震预测有一定前兆意义,是值得地震学界关注的问题。选取2008年5月12日汶川M_W 7.9地震发生前,临夏和湟源地震台分量应变仪记录与临夏、恩施和西安地震台数字地震仪记录以及临夏和周至地震台深井水位仪记录,分析发现,在临震前数天至数小时,上述各地震台不同学科观测仪器均记录到一些"跃变"和"震颤"震相。文中试图以颗粒物理原理,来认识不同距离、不同台站、不同学科的观测仪器在临震前相近时间段内记录的低频和高频震相,可能是不同地块在临震前发生预滑错动后激发的预滑震相Xp和地下气体在裂隙内流动激发的震颤震相Tp。观测结果表明：2008年5月8日03时至主震发生,各地震台所处地块在相近时段内逐次发生次数不等的预滑错动,其中1-2次较大错动可在噪声背景中被识别;各地震台预滑错动方向指向或背向主震震中。据此认为：汶川M_W 7.9地震前,上述各地震台所处地块在不同大小、不同方向的力链驱动下,发生指向或背向主震震中的临震预滑现象。  相似文献   

江苏地区渗流方位角变化特征分析     

鲍海英  李飞  蒋延龄  卜玉菲  韩丽 《地震地磁观测与研究》2018,39(6):114-119

利用谐波振幅和峰谷值2种方法,计算江苏地电台站渗流方位角,并尝试利用渗流方位角进行映震分析,结果表明：①使用2种方法计算的渗流方位角相差不大,由此所得地震对应关系应基本可靠;②高邮地电台渗流方位角与高邮-宝应M_S 4.9地震对应关系较好。因此,对江苏地区开展渗流方位角变化特征分析具有一定意义。  相似文献   

Targeted observation analysis of a Northwestern Tropical Pacific Ocean mooring array using an ensemble-based method     

Danian Liu  Jiang Zhu  Yeqiang Shu  Dongxiao Wang  Weiqiang Wang  Changxiang Yan  Wei Zhou 《Ocean Dynamics》2018,68(9):1109-1119

An important supplement for ocean observing systems, the Northwestern Tropical Pacific Ocean (NWTPO) mooring array including 15 moorings equipped with Acoustic Doppler Current Profilers (ADCP) devices was developed by the Chinese Academy of Sciences and deployed in 2013. This study assessed the performance of this mooring array in monitoring the intra-seasonal and low-frequency (above 91 days) variability of oceanic currents by conducting targeted observation analyses using an ensemble-based method. Key regions for monitoring intra-seasonal variability of the NWTPO circulation are the equator, Indonesian throughflow (ITF), headstream of the North Equatorial Countercurrent (NECC), and Subtropical Countercurrent (STCC). For monitoring intra-seasonal variability, the range of each mooring is confined to a local scale. Therefore, NWTPO moorings cannot adequately resolve intra-seasonal variability in areas of the ITF, the headstream of the NECC, and STCC due to location constraints of the moorings. For monitoring low-frequency variability of NWTPO circulation, the key regions are the Western Boundary Current (WBC), NECC, and the Equatorial Undercurrent (EUC). NWTPO moorings performed relatively well in monitoring the low-frequency variability, as indicated by the strong background correlations between each of the currents. The NWTPO mooring array plays an important role in monitoring the location and intensity of background currents. Because moorings are costly and require a high-density distribution for optimal performance, understanding the multi-timescale dynamical nature of the NWTPO current system is critical for the deploying future moorings in this region.  相似文献   

Modeling studies of tidal dynamics and the associated responses to coastline changes in the Bohai Sea,China     

Longhai Zhu  Rijun Hu  Haijun Zhu  Shenghui Jiang  Yongchen Xu  Nan Wang 《Ocean Dynamics》2018,68(12):1625-1648

Over the past 30 years, reclamation projects and related changes have impacted the hydrodynamics and sediment transport in the Bohai Sea. Three-dimensional tidal current models of the Bohai Sea and the Yellow Sea were constructed using the MIKE 3 model. We used a refined grid to simulate and analyze the effects of changes in coastline, depth, topography, reclamation, the Yellow River estuary, and coastal erosion on tidal systems, tide levels, tidal currents, residual currents, and tidal fluxes. The simulation results show that the relative change in the amplitude of the half-day tide is greater than that of the full-day tide. The changes in the tidal amplitudes of M₂, S₂, K₁, and O₁ caused by coastline changes accounted for 27.76–99.07% of the overall change in amplitude from 1987 to 2016, and water depth changes accounted for 0.93–72.24% of the overall change. The dominant factor driving coastline changes is reclamation, accounting for 99.55–99.91% of the amplitude changes in tidal waves, followed by coastal erosion, accounting for 0.05–0.40% of the tidal wave amplitude changes. The contribution of changes in the Yellow River estuary to tidal wave amplitude changes is small, accounting for 0.01–0.12% of the amplitude change factor. The change in the highest tide level (HTL) is mainly related to the amplitude change, and the correlation with the phase change is small. The dominant factor responsible for the change in the HTL is the tide amplitude change in M2, followed by S2, whereas the influence of the K1 and O1 tides on the change in the HTL is small. Reclamation resulted in a decrease in the vertical average maximum flow velocity (V_VAM) in the Bohai Sea. Shallower water depths have led to an increase in the V_VAM; deeper water depths have led to a decrease in the maximum flow velocity. The absolute value of the maximum flow velocity gradually decreases from the surface to the bottom, but the relative change value is basically constant. The changes in the tidal dynamics of the Bohai Sea are proportional to the degree of change in the coastline. The maximum and minimum changes in the tidal flux appear in Laizhou Bay (P-LZB) and Liaodong Bay (P-LDB), respectively. The changes in the tidal flux are related to the change in the area of the bay. Due to the reduced tidal flux, the water exchange capacity of the Bohai Sea has decreased, impacting the ecological environment of the Bohai Sea. Strictly controlling the scale of reclamation are important measures for reducing the decline in the water exchange capacity of the Bohai Sea and the deterioration of its ecological environment.  相似文献   

Study and application of PS-wave pre-stack migration in HTI media and an anisotropic correction method     

Li-Li Yan  Bing-Jie Cheng  Tian-Ji Xu  Ying-Ying Jiang  Zhao-Jun Ma  Jian-Ming Tang 《应用地球物理》2018,15(1):57-68

Anisotropy correction is necessary during the processing of converted PSwave seismic data to achieve accurate structural imaging, reservoir prediction, and fracture detection. To effectively eliminate the adverse effects of S-wave splitting and to improve PSwave imaging quality, we tested methods for pre-stack migration imaging and anisotropic correction of PS-wave data. We based this on the propagation rules of seismic waves in a horizontal transverse isotropy medium, which is a fractured medium model that reflects likely subsurface conditions in the field. We used the radial (R) and transverse (T) components of PS-wave data to separate the fast and slow S-wave components, after which their propagation moveout was effectively extracted. Meanwhile, corrections for the energies and propagation moveouts of the R and T components were implemented using mathematical rotation. The PS-wave imaging quality was distinctly improved, and we demonstrated the reliability of our methods through numerical simulations. Applying our methods to three-dimensional and three-component seismic field data from the Xinchang-Hexingchang region of the Western Sichuan Depression in China, we obtained high-quality seismic imaging with continuous reflection wave groups, distinct structural features, and specific stratigraphic contact relationships. This study provides an effective and reliable approach for data processing that will improve the exploration of complex, hidden lithologic gas reservoirs.  相似文献