Numerical study of upper ocean response to a typhoon moving zonally across the Luzon Strait

The Luzon Strait (LS) is a wide channel between Taiwan and the Luzon islands. Eastward of the LS, the Kuroshio Current (KC) flows northward along the eastern coasts of Luzon and Taiwan. A typhoon is a strong and localized low-pressure weather system that occurs frequently in the vicinity of the Taiwan area. One typical typhoon track, passing through the seas surrounding Taiwan, is a zonal path across the LS. The satellite measured SST, corresponding to typhoons Pabuk (5 Aug. 2007–12 Aug. 2007) and Dujuan (29 Aug. 2003–5 Sep. 2003), which both moved along this path, demonstrated that a classic right bias cooling occurs to the north of the storm track, during the typhoon forced period. However, some cold anomaly water also present toward left (south) of the storm track east of the LS in the relaxation period. This paper adopted a three-dimensional hydrostatic primitive equation model to study the possible causes of this southward transport of cold waters. Both model results and the observed SST anomaly revealed that the strength of the upper ocean cooling depends on whether a resonant regime between the typhoon winds and the near-inertial currents can be excited. To the east of the LS, the convergence between the warm Kuroshio water and the cold wakes in the poststorm period will enhance the southward spreading of cold anomaly water. The enhanced vertical mixing, induced by the southward propagation of nearly inertial waves associated with the cold wakes, can also produce some cold anomaly to the south of a storm track in the poststorm period. Both mechanisms can contribute to the occurrence of some cold anomaly water to the south of the storm track east of the KC. To the west of the LS, the convergence between the warm Kuroshio water and the cold upwelling water from the northern South China Sea can further strengthen the Kuroshio front in the LS.     

A laboratory study on the undrained strength of a silty sand from Central Western Taiwan

The sand deposit in Central Western Taiwan typically contained significant amounts of fines. The assessment of liquefaction potential using the simplified procedure often involved adjustment in field test results to account for the effects of fines. The available fines content (FC) adjustment methods are highly empirical and may lead to very different conclusions. The need and/or level of FC adjustment should be justified based on cyclic behavior of sand and its relationship with fines. This study made an attempt to provide that reference information for a silty sand commonly found in Central Western Taiwan. A series of isotropic consolidation, undrained monotonic and cyclic triaxial tests were conducted on reconstituted Mai Liao Sand (MLS) with various FCs and densities. Concurrent shear wave velocities were measured using bender elements in some of the cyclic triaxial tests. This paper describes the geological background, the laboratory tests and their implications in the assessment of liquefaction potential for MLS.     

Dam overtopping risk assessment considering inspection program

Safety inspection of large dams in Taiwan is conducted every 5 years. The practice does not take into consideration uncertainty of dam conditions. The goal of this study is to determine the optimal dam inspection interval under the consideration of overtopping risk incorporating uncertainty gate availability. In earlier studies, assessment of overtopping risk only considered the uncertainties in reservoir properties and natural randomness of hydrologic events without giving much thought to the availability of spillway gates. As a result, the overtopping risk could be underestimated. In this study, an innovative concept is proposed to evaluate dam overtopping by taking into account spillway gate availability. The framework consists of three parts: (1) evaluation of conditional overtopping risk for different numbers of malfunctioning spillway gates; (2) evaluation of spillway gate availability; and (3) dam inspection scheduling. Furthermore, considerations are given to overtopping risk, inspection cost, and dam break cost for determining the optimal inspection schedule. The methodology is applied to the Shihmen Reservoir in Taiwan and to evaluate its time-dependent overtopping risk. Results show that overtopping risk considering the availability of the spillway gates is higher than the one without considering the availability of the spillway gates.     

东帝汶海槽断裂特征与构造演化模式

东帝汶海槽位于澳大利亚板块西北帝汶海与帝汶岛之间,晚中新世澳大利亚板块与东南亚班达岛弧碰撞引发了帝汶岛与帝汶海槽的构造变形,由于弧-陆碰撞过程的复杂性,帝汶海槽的变形时间与机制仍然存在较大争议。为约束帝汶海槽变形时间、探讨其演化过程,依据二维地震数据,对东帝汶海槽的断裂特征进行定量分析,并结合钻井与天然地震事件探讨弧-陆碰撞背景下帝汶海槽的构造演化模式。研究结果表明,晚中新世（约6 Ma）澳大利亚板块与班达岛弧碰撞,引发了帝汶岛的隆升与帝汶海槽的沉降,变形持续至晚上新世（约3 Ma）,形成现今帝汶海槽形态。现今澳大利亚板块与班达岛弧之间的相对运动速率已逐渐减小趋于停止,未来二者可能会以一个整体继续向北运动。     

深反射地震揭示喜马拉雅地区地壳上地幔的复杂结构

报告了中、美两国在喜马拉雅山区进行的第一次深反射地震试验的结果．试验剖面南起喜马拉雅山山脊南亚东县的帕里镇,向北穿过喜马拉雅山脊的荡拉,到达康马南的萨马达．剖面长约１００ｋｍ．共中心点（ＣＭＰ）叠加剖面上显示出：１．在地壳中部有一强反射带,向北缓倾斜下去,延长达１００ｋｍ以上．它可能代表了一个活动的逆冲断裂或是一条巨大的拆离带,印度地壳整体或下地壳沿此拆离层俯冲到藏南之下．２．上部地壳的反射很丰富,显示了上地壳存在着大规模的叠瓦状结构．３．下地壳的反射同相轴呈现短而有规律的分布,显示了塑性流变特征．４．在测线南部莫霍反射明显,深度达７２－７５ｋｍ．发现南部有双莫霍层的存在．５．试验中还取得莫霍层下面３２,３８,４８ｓ等双程走时的多条反射,向北倾斜,反射同相轴延续较长,信息丰富,反映了上地幔的成层结构和变形特征．这些结果对印度大陆地壳整体或其下地壳俯冲到藏南特提斯喜马拉雅地壳之下,并导致西藏南端地壳增厚的观点,给予了实质性的支持．     

泥石流危险范围预测模型及在昆明东川城区的应用

结合泥石流危险范围模型实验数据,运用多元回归分析方法探讨了泥石流危险范围预测,并进行了误差分析。以昆明市东川城区后山3条泥石流沟为例,运用该模型对其危险范围进行了预测分析,为东川城区泥石流防灾提供了科学依据。     

大型构筑物GNSS监测多路径探测及消除方法研究

本文分析了多路径效应产生的原因及其信号特征,利用相同环境下,相邻周期相同时刻的GNSS观测数据多路径误差应有强相关性的特征,采用逐个观测历元差分和卡尔曼滤波相结合的方法来消弱多路径效应的影响,从而提高大型构筑物GNSS监测的成果精度。     

广东省大宝山铜矿成矿预测空间数据库建设及成矿信息提取

大宝山矿床是我国著名多金属矿床之一,其中铁、铜硫、钨钼等元素均达到大型规模。据记载,唐宋时期古人即在此开采。随着社会经济的不断发展,矿产开采量的不断加剧,数百年的开采使得矿区内已探明的铁、铜硫、钨钼等多金属矿产资源储量日益枯竭。因此,矿山外围、深部找矿勘探增储工作显得非常迫切。然而,数百年的勘查与开采使得矿区积累了大量的地、物、化、遥数据,从而迫切的需要建立地学空间数据库,对多源空间数据进行科学有效地管理;为成矿信息的提取研究提供可能性。鉴于传统数据库不适应于高效的管理多源数据库,且GIS技术以其高效的数据管理及强大的空间数据处理能力,为多源数据集成找矿提供了一个科学的平台,在成矿信息提取及成矿预测评价中的应用越来越受到国内外学者的高度重视。本文运用ArcSDE Geodatabase和Oracle空间数据库技术,从概念设计、逻辑结构设计、物理设计3大方面系统介绍了大宝山地学空间数据库的设计过程;从图形库的建立、属性库的建立、图形库与属性库的关联3个方面介绍了空间数据库的建立过程,进而完成了大宝山铜矿成矿信息的空间数据库建库工作;完成对成矿数据进行科学有效地存储、查询、处理、运算及更新等操作,从而实现了基于GIS与SDM相结合的技术从数据库中对遥感热液蚀变、地质、物探、化探等有用成矿信息的提取;最终利用SKUA-GOCAD三维平台将多源数据进行三维可视化显示。研究成果可为生产矿山开展的外围、深部找矿勘探工作提供依据。     

Review of Methodologies for Offshore Wind Resource Observation and Assessment

Observation and assessment of wind resources is a prerequisite for wind farm construction. Due to the investment cost of offshore wind farm is very expensive, more accurate assessment of wind resources is needed to reduce their investment risks. From traditional field observation to multi-platform remote sensing and from ordinary mathematical statistics to coupled numerical model simulation, abundant offshore wind data and evolving assessment methods make the results of offshore wind resource assessment more and more reliable. Poor station observations and rich remote sensing data are distinct characteristics of offshore wind data. Technology integration of applying multi-scale coupled models to assimilate multi-source remote sensing and station data is a mainstream development direction of offshore wind resource assessment methods. The wind resource assessment for offshore wind farm should focus on data quality and method selections of data interpolation, wind speed calculation of return period and wind energy parameters adjusted for a long term condition because these factors can significantly affect the operating efficiency of future wind farm.     

Gravity anomalies of the ridge-transform system in the South Atlantic between 31 and 34.5° S: Upwelling centers and variations in crustal thickness

To decipher the distribution of mass anomalies near the earth's surface and their relation to the major tectonic elements of a spreading plate boundary, we have analyzed shipboard gravity data in the vicinity of the southern Mid-Atlantic Ridge at 31–34.5° S. The area of study covers six ridge segments, two major transforms, the Cox and Meteor, and three small offsets or discordant zones. One of these small offsets is an elongate, deep basin at 33.5° S that strikes at about 45° to the adjoining ridge axes.By subtracting from the free-air anomaly the three-dimensional (3-D) effects of the seafloor topography and Moho relief, assuming constant densities of the crust and mantle and constant crustal thickness, we generate the mantle Bouguer anomaly. The mantle Bouguer anomaly is caused by variations in crustal thickness and the temperature and density structure of the mantle. By subtracting from the mantle Bouguer anomaly the effects of the density variations due to the 3-D thermal structure predicted by a simple model of passive flow in the mantle, we calculate the residual gravity anomalies. We interpret residual gravity anomalies in terms of anomalous crustal thickness variations and/or mantle thermal structures that are not considered in the forward model. As inferred from the residual map, the deep, major fracture zone valleys and the median, rift valleys are not isostatically compensated by thin crust. Thin crust may be associated with the broad, inactive segment of the Meteor fracture zone but is not clearly detected in the narrow, active transform zone. On the other hand, the presence of high residual anomalies along the relict trace of the oblique offset at 33.5° S suggests that thin crust may have been generated at an oblique spreading center which has experienced a restricted magma supply. The two smaller offsets at 31.3° S and 32.5° S also show residual anomalies suggesting thin crust but the anomalies are less pronounced than that at the 33.5° S oblique offset. There is a distinct, circular-shaped mantle Bouguer low centered on the shallowest portion of the ridge segment at about 33° S, which may represent upwelling in the form of a mantle plume beneath this ridge, or the progressive, along-axis crustal thinning caused by a centered, localized magma supply zone. Both mantle Bouguer and residual anomalies show a distinct, local low to the west of the ridge south of the 33.5° S oblique offset and relatively high values at and to the east of this ridge segment. We interpret this pattern as an indication that the upwelling center in the mantle for this ridge is off-axis to the west of the ridge.