中国城市抗御地震灾害研究的发展与实践

城市是社会发展的产物，它具有人口密集、经济发达、基础设施集中等特点。城市安全一直是人们普遍关心的问题，城市地震安全受到政府和社会的广泛关注，并且是学术界研究的热点问题之一。唐山大地震后，在反思惨痛震害教训的同时，中国政府和学术界开始了长达40余年的城市抗御地震灾害的研究与实践，形成了有中国特色的城市抗震防灾技术和方法。本文简要地归纳了破坏性地震对城市的影响，从我国先后开展的城市抗震防灾规划、防震减灾规划和韧性城市3个方面系统地总结了中国城市抗御地震灾害研究和实践的发展历程，讨论和评述了在这一研究领域存在的问题。本文对韧性城市的定义、研究内容、特征、评价指标和方法进行了较为详细的介绍，在此基础上，提出了在城市抗震中应重点加强研究的5个方面的问题和今后的研究方向。     

Study on the Natural Mineral Water Resource Bearing Capacity and its Driving Factors in Fusong County,Changbai Mountain Area,Jilin Province of China

Water Resources - In order to maintain the sustainable exploitation of the natural mineral water resources in Changbai Mountain Area with the continuously increasing exploitation intensity,...     

Geophysical Signature of the Shallow Water Flow in the Deepwater Basin of the Northern South China Sea

Shallow water flow (SWF), a disastrous geohazard in the continental margin, has threatened deepwater drilling operations. Under overpressure conditions, continual flow delivering unconsolidated sands upward in the shallow layer below the seafloor may cause large and long-lasting uncontrolled flows; these flows may lead to control problems and cause well damage and foundation failure. Eruptions from over-pressured sands may result in seafloor craters, mounds, and cracks. Detailed studies of 2D/3D seismic data from a slope basin of the South China Sea (SCS) indicated the potential presence of SWF. It is commonly characterized by lower elastic impedance, a higher Vp/Vs ratio, and a higher Poisson’s ratio than that for the surrounding sediments. Analysis of geological data indicated the SWF zone originated from a deepwater channel system with gas bearing over-pressured fluid flow and a high sedimentation rate. We proposed a fluid flow model for SWF that clearly identifies its stress and pressure changes. The rupture of previous SWF zones caused the fluid flow that occurred in the Baiyun Sag of the northern SCS.     

Research on the Application of Fast-steering Mirror in Stellar Interferometers

In stellar interferometers, the fast-steering mirror (FSM) is widely utilized to correct the wavefront tilt caused by the atmospheric turbulence and internal instrumental vibration, because of its high resolution and fast response frequency. In this study, the non-coplanar error between the FSM and the actuator deflection axis introduced by the manufacturing, assembly, and adjustment is analyzed systematically. Via a numerical method, the additional optical path difference (OPD) caused by the above factors is studied, and its effect on the fringe tracking accuracy of a stellar interferometer is also discussed. On the other hand, the starlight parallelism between the beams of two arms is one of the main factors for the loss of fringe visibility. By analyzing the influence of wavefront tilt caused by the atmospheric turbulence on fringe visibility, a simple and efficient real-time correction scheme of starlight parallelism is proposed based on a single array detector. The feasibility of this scheme is demonstrated by a laboratory experiment. The results show that after the correction of fast-steering mirror, the starlight parallelism meets preliminarily the requirement of a stellar interferometer on the wavefront tilt.     

Effects of Anthropogenic Disturbance on Sediment Organic Carbon Mineralization Under Different Water Conditions in Coastal Wetland of a Subtropical Estuary

The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to investigate the effects of anthropogenic disturbance(aquaculture pond, pollutant discharge and agricultural activity) on soil organic C mineralization under different water conditions in the Minjiang River estuary wetland, Southeast China. The results showed that the organic C mineralization in the wetland soils was significantly affected by human disturbance and water conditions(P 0.001), and the interaction between human disturbance activities and water conditions was also significant(P 0.01). The C mineralization rate and the cumulative mineralized carbon dioxide-carbon(CO_2-C)(at the 49th day) ranked from highest to lowest as follows: Phragmites australis wetland soil aquaculture pond sediment soil near the discharge outlet rice paddy soil. This indicated that human disturbance inhibited the mineralization of C in soils of the Minjiang River estuary wetland, and the inhibition increased with the intensity of human disturbance. The data for cumulative mineralized CO_2-C showed a good fit(R~2 0.91) to the first-order kinetic model C_t = C_0(1 – exp(–kt)). The kinetic parameters C_0, k and C_0 k were significantly affected by human disturbance and water conditions. In addition, the total amount of mineralized C(in 49 d) was positively related to C_0, C_0 k and electrical conductivity of soils. These findings indicated that anthropogenic disturbance suppressed the organic C mineralization potential in subtropical coastal wetland soils, and changes of water pattern as affected by human activities in the future would have a strong influence on C cycling in the subtropical estuarine wetlands.     

基于多源遥感数据的日本海内波特征研究

日本海特殊的地理位置和复杂的地形使得该海域内波表征极为复杂，遥感是大范围观测内波的有效手段，已被广泛应用于内波的探测研究。本文利用MODIS、GF-1和ENVISAT ASAR遥感影像，开展了日本海内波特征研究。通过提取内波波峰线，生成了日本海内波空间分布图；获取了内波的波峰线长度和传播速度，并基于非线性薛定谔方程反演了内波振幅。研究结果表明，日本海内波分布范围宽广，不仅大陆架沿海区内波分布密集，深海盆地也探测到了大量内波；日本海北部45°N附近海域有少量内波出现，利用高分影像探测到朝鲜陆架浅海区有大量小尺度内波，大和海盆、大和隆起的西南部海域没有发现内波。日本海内波波峰线长达100多千米，深海区的传播速度大于1 m/s；浅海区内波振幅约10 m左右，深海区可达60 m以上。     

超慢速扩张环境下超镁铁质岩系统的热液硫化物成矿机理以及启示

西南印度洋63.5°E热液区是在超慢速扩张洋脊发现的首个超镁铁质岩热液系统。对取自该区的热液硫化物样品进行了系统的矿物学和地球化学分析，矿物学分析结果表明:该热液区硫化物为富Fe型高温硫化物，且经历了较深程度的氧化蚀变，大量中间态的Fe氧化物充填在硫化物矿物间的孔隙及内部解理中；这些硫化物相以白铁矿为主，其次是等轴古巴矿和少量铜蓝，缺乏黄铁矿、闪锌矿。据推断，该区的热液成矿作用分为4个阶段:低温白铁矿阶段→高温等轴古巴矿阶段→自形白铁矿阶段→后期海底风化阶段（少量铜蓝以及大量的Fe的羟氧化物）。与之相对应，地球化学分析结果表明这些硫化物的Fe含量较高（31.57%~44.59%），Cu含量次之（0.16%~7.24%），而Zn含量普遍较低（0.01%~0.11%）；微量元素较为富集Co（328×10-6~2 400×10-6）和Mn（48.5×10-6~1 730×10-6）。该区硫化物中较高含量的Fe、Co与超镁铁质岩热液系统相似，明显高于镁铁质岩热液系统。独特的热液硫化物矿物学特征和元素组成可能与该区普遍出露的地幔岩、橄榄岩蛇纹石化作用以及拆离断层的广泛发育的环境有关。     

Photometric Follow-up Transit (Primary Eclipse) Observations of WASP-43 b and TrES-3b and A Study on Their Transit Timing Variations

Two photometric follow-up transit (primary eclipse) observations on WASP-43 b and four observations on TrES-3 b are performed using the Xuyi Near-Earth Object Survey Telescope. After differential photometry and light curve analysis, the physical parameters of the two systems are obtained and are in good match with the literature. Combining with transit data from a lot of literature, the residuals (O ? C) of transit observations of both systems are fitted with the linear and quadratic functions. With the linear fitting, the periods and transit timing variations (TTVs) of the planets are obtained, and no obvious periodic TTV signal is found in both systems after an analysis. The maximum mass of a perturbing planet located at the 1:2 mean motion resonance (MMR) for WASP-43 b and TrES-3 b is estimated to be 1.826 and 1.504 Earth mass, respectively. By quadratic fitting, it is confirmed that WASP-43 b may have a long-term TTV which means an orbital decay. The decay rate is shown to be P? = (?0.005248 ± 0.001714) s·yr^?1, and compared with the previous results. Based on this, the lower limit of the stellar tidal quality parameter of WASP-43 is calculated to be ${Q^{\prime }}_{*}\ge 1.5\times {10}^5$, and the remaining lifetimes of the planets are presented for the different ${Q^{\prime }}_{*}$ values of the two systems, correspondingly.     

Leak-off mechanism and pressure prediction for shallow sediments in deepwater drilling

Deepwater sediments are prone to loss circulation in drilling due to a low overburden gradient. How to predict the magnitude of leak-off pressure more accurately is an important issue in the protection of drilling safety and the reduction of drilling cost in deep water. Starting from the mechanical properties of a shallow formation and based on the basic theory of rock-soil mechanics, the stress distribution around a borehole was analyzed. It was found that the rock or soil on a borehole is in the plastic yield state before the effective tensile stress is generated, and the effective tangential and vertical stresses increase as the drilling fluid density increases; thus, tensile failure will not occur on the borehole wall. Based on the results of stress calculation, two mechanisms and leak-off pressure prediction models for shallow sediments in deepwater drilling were put forward, and the calculated values of these models were compared with the measured value of shallow leak-off pressure in actual drilling. The results show that the MHPS (minimum horizontal principle stress) model and the FIF (fracturing in formation) model can predict the lower and upper limits of leak-off pressure. The PLC (permeable lost circulation) model can comprehensively analyze the factors influencing permeable leakage and provide a theoretical basis for leak-off prevention and plugging in deepwater drilling.