北京市地面沉降发展及对城市建设的影响

地面沉降是北京市平原区主要地质灾害之一,最早在1935年发现于西单至东单一带,到目前为止已经形成了多个地面沉降中心,到2005年底,累计沉降量大于50mm的沉降区达4114 km~2,大于100mm的沉降区达2815km~2。地面沉降已经对城市基础设施造成一定程度的破坏,并且已经对奥运场馆、规划新城、CBD等重要区域构成潜在威胁,所以必须及时制定完善的防治措施来降低地面沉降的危害。     

北祁连西段吊达坂地区水系沉积物地球化学特征及找矿预测

以北祁连西段吊达坂水系沉积物测量地球化学特征为研究对象，通过元素含量的概率分布、元素富集与分异、单元素异常、元素相关性分析及异常元素组合等特征的研究，在区内共圈定综合地球化学异常18处，划分出3个铜铅锌多金属找矿远景区，发现矿点4处。研究结果显示水系沉积物测量在北祁连西段半干旱高寒山区找矿效果明显。     

UPPER CRUSTAL VELOCITY STRUCTURE AND CONSTRAINING FAULT INTERPRETATION FROM SHUNYI-TANGGU REFRACTION EXPERIMENT DATA

The urban active fault survey is of great significance to improve the development and utilization of urban underground space, the urban resilience, the regional seismic reference modeling, and the natural hazard prevention. The Beijing-Tianjin metropolitan region with the densest population is one of the most developed and most important urban groups, located at the northeastern North China plain. There are several fault systems crossing and converging in this region, and most of the faults are buried. The tectonic setting of the faults is complex from shallow to deep. There are frequent historical earthquakes in this area, which results in higher earthquake risk and geological hazards. There are two seismicity active belts in this area. One is the NE directed earthquake belt located at the east part of the profile in northern Ninghai near the Tangshan earthquake region. The other is located in the Beijing plain in the northwest of the profile and near the southern end of Yanshan fold belt, where the 1679 M8.0 Sanhe-Pinggu earthquake occurred, the largest historical earthquake of this area. Besides, there are some small earthquake activities related to the Xiadian Fault and the Cangdong Fault at the central part of the profile.
The seismic refraction experiment is an efficient approach for urban active fault survey, especially in large- and medium-size cities. This method was widely applied to the urban hazard assessment of Los Angeles. We applied a regularized tomography method to modeling the upper crustal velocity structure from the high-resolution seismic refraction profile data which is across the Beijing-Tianjin metropolitan region. This seismic refraction profile, with 185km in length, 18 chemical explosive shots and 500m observation space, is the profile with densest seismic acquisition in the Beijing-Tianjin metropolitan region up to now. We used the trial-error method to optimize the starting velocity model for the first-arrival traveltime inversion. The multiple scale checker board tests were applied to the tomographic result assessment, which is a non-linear method to quantitatively estimate the inversion results. The resolution of the tomographic model is 2km to 4km through the ray-path coverage when the threshold value is 0.5 and is 4km to 7km through the ray-path coverage when the threshold value is 0.7. The tomographic model reveals a very thick sediment cover on the crystalline basement beneath the Beijing-Tianjin metropolitan region. The P wave velocity of near surface is 1.6km/s. The thickest sediment cover area locates in the Huanghua sag and the Wuqing sag with a thickness of 8km, and the thinnest area is located at the Beijing sag with a thickness of 2km. The thickness of the sediment cover is 4km and 5km in the Cangxian uplift and the Dacang sag, respectively. The depth of crystalline basement and the tectonic features of the geological subunits are related to the extension and rift movement since the Cenozoic, which is the dynamics of formation of the giant basins.
It is difficult to identify a buried fault system, for a tomographic regularization process includes velocity smoothing, and limited by the seismic reflection imaging method, it is more difficult to image the steep fault. Velocity and seismic phase variations usually provide important references that describe the geometry of the faults where there are velocity differences between the two sides of fault. In this paper, we analyzed the structural features of the faults with big velocity difference between the two sides of the fault system using the velocity difference revealed by tomography and the lateral seismic variations in seismograms, and constrained the geometry of the major faults in the study region from near surface to upper crust. Both the Baodi Fault and the Xiadian Fault are very steep with clear velocity difference between their two sides. The seismic refraction phases and the tomographic model indicate that they both cut the crystalline basement and extend to 12km deep. The Baodi Fault is the boundary between the Dachang sag and the Wuqing sag. The Xiadian Fault is a listric fault and a boundary between the Tongxian uplift and the Dachang sag. The tomographic model and the earthquake locations show that the near-vertical Shunyi-Liangxiang Fault, with a certain amount of velocity difference between its two sides, cuts the crystalline basement, and the seismicity on the fault is frequent since Cenozoic. The Shunyi-Liangxiang Fault can be identified deep to 20km according to the seismicity hypocenters.
The dense acquisition seismic refraction is a good approach to construct velocity model of the upper crust and helpful to identify the buried faults where there are velocity differences between their two sides. Our results show that the seismic refraction survey is a useful implement which provides comprehensive references for imaging the fault geometry in urban active fault survey.     

船舶转向避让碰撞距离模型的确定

船舶碰撞距离直接影响船舶碰撞危险度的大小。分析了影响船舶碰撞距离的因素:会遇 态势、船舶的操纵性能、船舶尺度、船舶速度等;给出目标船静止不动时和目标船有运动速度时的 船舶转向避让时碰撞距离数学模型,为研究船舶碰撞危险度和船舶自动避碰决策系统提供理论依 据。     

南极普里兹湾及其邻近海域表层水镭同位素的分布及应用

中国第27次南极科学考察期间(2010年12月30日至2011年1月16日),对普里兹湾及其邻近海域表层海水进行了226Ra和228Ra的分析,结果表明:226Ra和228Ra比活度的变化范围分别为1.47—2.43Bq/m3和0.17—0.45Bq/m3,平均值分别为2.13Bq/m3和0.29Bq/m3,228Ra/226Ra)A.R.(228Ra与226Ra的活度比)的变化范围为0.08—0.20,平均值为0.14。根据盐度和226Ra的质量平衡方程,计算出研究海域表层水中冰融水、南极夏季表层水和普里兹湾中深层水的份额。研究海域表层水中温度、盐度、226Ra、228Ra、228Ra/226Ra)A.R.和冰融水份额的空间分布显示,在埃默里冰架前沿海域,西侧海域较东侧海域具有低温、高盐、高226Ra、低228Ra、低228Ra/226Ra)A.R.、低冰融水份额的特征,证实埃默里冰架下水体东进西出的运动规律。根据埃默里冰架前沿东、西侧水体228Ra/226Ra)A.R.的差异,估算出埃默里冰架下表层水体东进西出所经历的时间为1.85a。此外,在普里兹湾湾口中部海域(66.5—67.5°S,72°—74°E),观察到次表层水的上升通风作用,该区域较高的228Ra含量和228Ra/226Ra)A.R.证明这些表层水体并非来自湾外绕极深层水的上涌,而可能来自湾内埃默里冰架输出水体。     

裂片石莼营养价值的评价及其多糖制备的初步研究

对采自福建的野生裂片石莼(Ulva fasciata)进行了分类学鉴定和营养价值评估;采用微波加热新方法,进一步研究了裂片石莼多糖提取工艺。研究结果表明,裂片石莼的总糖、粗蛋白质、总氨基酸和总脂含量分别为34.38%、27.60%、25.20%、11.70%;其必需氨基酸含量为10.0%,氨基酸比值系数分(SRC)=79.77;裂片石莼的重金属元素含量达到国家海藻制品的限量标准。研究结果还表明,通过正交实验优化微波加热提取工艺,与传统加热提取工艺相比,裂片石莼多糖的得率提高了21.35%,而耗能降低了58.51%。     

逐步回归分析在渤海海冰等级预报中的应用

根据1951—2013年渤海海冰等级资料,利用最大熵谱法分析了渤海海冰等级的周期,结果表明渤海海冰具有明显的年际和年代际变化特征,其主要周期为2—7年和11年。相关分析及逐步回归分析表明:渤海海冰的年际变化与西太平洋副高面积及北界指数、太平洋副高面积指数、亚洲区极涡面积指数以及南方涛动指数都有显著的相关关系。利用逐步回归分析方法建立的海冰预报模型经过拟合和试预报都得到了很好的结果,具有较高的可信度。     

物理海洋传感器现状及未来发展趋势

文中对目前我国物理海洋要素观测传感器技术发展现状进行了分析。在国家科技计划支持下,我国的物理海洋观测传感器技术取得了快速发展,但与国际上先进的传感器技术水平相比,国内具有自主知识产权的传感器仍有较大差距。随着未来海洋观测需求的不断发展,小型、轻重量、低功耗、高精度、高灵敏、智能化新型传感器必将是今后5~10年研究与开发的重点。     

海水盐度对沉降泥沙固结过程影响研究

黄河每年输送上亿吨泥沙入海,其中80%以上沉积在河口附近水下三角洲。受黄河入海径流量、气候及海洋动力条件影响,黄河口海域海水盐度变化显著。目前,不同盐度海水环境下入海泥沙沉降形成的海床土,固结过程有何差异尚不清楚。本文在黄河水下三角洲潮坪配制不同盐度的流态沉积物,模拟不同沉积环境下新沉积土的固结过程,利用轻型贯入测试、十字板剪切测试等现场原位试验,实时观测沉积环境盐度对沉降泥沙固结过程的影响。研究发现:随着海水盐度增加,沉积物固结强度增大,沉积环境盐度每增高1‰,沉积物固结后强度可增加0.15倍;海水盐度对沉积物固结速率的影响,在初始阶段表现不明显,在沉积物固结后期,盐度每增高1‰,固结速率可增长1.23倍;海水盐度的增高,还加剧了沉积物固结强度的空间非均匀性。本研究的发现,促进了对河口区海底工程环境的认识。     

东昆仑地区中生代熔融、同化、存储和均一(MASH)过程及壳幔岩浆混合

哈西亚图石英闪长岩是东昆仑地区中生代具幔源组分贡献的花岗岩类典型代表,岩体出露于东昆仑中构造带,广泛发育暗色微粒包体。包体为闪长质岩石,并含有一系列岩浆混合成因的证据,如水滴状、长条状塑性流变外形,淬冷边、反向脉等高—中温混合迹象,以及低Mg/(Fe+Mg)、Na/(Ca+Na)值等混合成因特征。包体A/CNK值介于0.77~0.87,属准铝质,富Al2O3、Fe2O3、MgO,贫K2O、Na2O,富集大离子亲石元素(Rb、Ba、K等),同时又具有Ta、Nb、Ti的"TNT"负异常,具有俯冲带幔源岩石的成分特点。依据岩石学、地球化学特征并结合同时期大地构造背景,东昆仑晚古生代—早中生代含暗色微粒包体花岗质岩石是幔源岩浆经历多次熔融、同化、存储和均一(MASH)过程后与壳源岩浆混合的产物。在混合岩浆中,富镁铁质端元是由辉长质岩浆进化而来的闪长质岩浆。