利用高精度重磁法对“羊里磁异常”的解释探讨

"羊里磁异常"自1967年发现以来,由于所处地质环境为矽卡岩型铁矿成矿有利地段,且紧邻已知的温石埠铁矿,以及"羊里磁异常"规模较大且具备低缓磁异常的特点,一直受到地质界的广泛关注,地勘单位在该区做了大量的铁矿找矿工作,但对"羊里磁异常"勘查中一直未取得突破性进展,该文从高精度重磁角度对"羊里磁异常"进行了定量解释以及定量计算,并通过钻探验证等技术手段,进一步推断"羊里磁异常"是由古近纪含磁铁碎屑的砂砾岩以及闪长岩共同引起的,对该异常的认识更进了一步。     

Rift fault geometry and evolution in the Cretaceous Potiguar Basin (NE Brazil) based on fault growth models

We investigated the Cretaceous Potiguar Basin in the Equatorial margin of Brazil to understand how the geometry of major faults evolved to form the basin internal architecture. Previous studies pointed out that the rift is an asymmetrical half-graben elongated along the NE-SW direction. We used 2D seismic, well logs and 3D gravity modeling to analyze faults that constitute the rift boundary and determine their maximum displacement (D_max) and length (L) ratio in the Potiguar Rift. We constrained the 3D gravity modeling with well data and the interpretation of seismic sections. The difference of the fault displacement and depth of the basement obtained in the gravity model is in the order of 10% compared to seismic and well data. The fault-growth curves allowed us to divide the faulted rift border into four main fault systems, which provide roughly similar D_max/L ratios. Fault-growth curves suggest that a regional uniform tectonic mechanism influenced growth of these faults. These fault systems are composed of minor faults that we define as segments. The variation of the displacements along the fault segments indicates that the fault systems were formed independently during rift initiation and were linked by hard and soft linkages. The latter formed relay ramps. In the interconnection zones the D_max/L ratios are highest due to interference of fault segment motions. We divided the evolution of the Potiguar Rift into five stages based on these ratios and correlated them with the major tectonic stages of the breakup between South America and Africa in the Early Cretaceous.     

基于LiDAR的海原断裂松山段断错地貌分析与古地震探槽选址实例

基于高精度机载Li DAR数据在GIS平台的地貌因子渲染分析,对海原断裂老虎山段松山地区古地震研究点进行高精度大比例尺(1∶1000)地貌填图,勾勒出研究点微地貌空间展布和断裂高精度几何形态。通过对松山古地震研究点2个新探槽的开挖,结合细致的探槽解译、地震事件识别与分期、年代学样品测试,得出5次37380±880BP以内的不连续古地震序列。通过对比此处已经开挖的各自相距不足150m、分布于断裂同一段落的4个古地震探槽的微地貌位置、沉积特征和地震事件信号强弱,发现即使相距不远,不同微地貌位置古地震探槽揭示的古地震现象也会有显著差别。这种差别凸显了古地震研究结果,如揭示的事件证据和个数等与探槽点位置的选取有较强的依赖性。综合对比分析表明,较低的地势、低能静水环境、高沉积速率、细粒的沉积物源区及连续的沉积环境是走滑断裂上开展古地震研究的优选地貌位置。实例表明,基于高精度地形数据对研究点开展精细地貌填图揭示微地貌时空演化,从而在探槽开挖前对古地震研究点的构造地貌优劣进行充分评价是提高古地震研究质量的必要程序,同时也显示出高精度机载Li DAR数据在活动构造研究中的重要新应用。     

瓦南矿区钒钛磁铁矿重力、可控源综合勘查应用效果

瓦南基性-超基性岩型钒钛磁铁矿具有高磁高密低阻特性,具备开展物探勘查的前提。在地面磁测圈定的磁异常部位开展了重力、可控源音频大地电磁(CSAMT)综合剖面勘查,结合成矿规律研究成果进行了联合解译,推断了深部隐伏矿体的位置。在综合物探异常部位钻探发现了厚度40m以上的钒钛磁铁矿体,取得了良好的找矿效果。     

奇异值分解(SVD)在位场数据去噪中的应用

根据奇异值分解原理,分析其在位场去噪中的可行性,提出了一种判断有效阶次k的方法。对多边形厚板模型的重力异常进行奇异值分解去噪和小波去噪效果的对比,证明了奇异值分解去噪的有效性和优势。将其应用于实测重力数据的处理中,取得较好的效果。理论模型和实测资料的处理结果表明:基于奇异值分解的去噪方法可以有效地去除随机噪声,提高数据处理和解释的精度。     

异重流沉积研究进展

在相关文献调研基础上,综述了异重流沉积研究现状,并结合中生代湖相异重岩研究实例,建立了“沟道-舌状体-朵状体”异重流沉积模式。异重流(hyperpycnal flow)是一种由洪水期河口直接注入、因密度大于汇水盆地水体密度而沿水体底部分层流动的持续型浊流。它呈牛顿流变性质、紊乱流动状态、湍流支撑机制,具有更高的发生频率和稳定的沉积物供给。异重流主要受地形、气候、密度差等因素控制,海洋和湖泊均有发生;水体密度小、近物源、地形高差大、中-小河流发育、构造活动强烈的陆相淡水湖泊更利于异重流的产生,但陆相湖盆异重流沉积并未引起足够的重视。异重流自近端向远端总体呈稀释趋势,依次对应于特定的沉积构造及序列;由异重流形成的沉积岩被称作异重岩(hyperpycnite),以发育由洪水增强-减弱所产生的逆粒序-正粒序组合、层内微侵蚀面、富含陆源有机质区别于其他浊积岩。深入研究异重流沉积,不仅有益于完善重力流沉积理论、分析沉积环境,而且有利于指导深水非常规油气勘探,具有重要的科学价值和现实意义。     

Impact of cyclone Nilam on tropical lower atmospheric dynamics

A deep depression formed over the Bay of Bengal on 28 October 2012, and developed into a cyclonic storm. After landfall near the south coast of Chennai, cyclone Nilam moved north-northwestwards. Coordinated experiments were conducted from the Indian stations of Gadanki(13.5?N, 79.2?E) and Hyderabad(17.4?N, 78.5?E) to study the modification of gravity-wave activity and turbulence by cyclone Nilam, using GPS radiosonde and mesosphere–stratosphere–troposphere radar data. The horizontal velocities underwent large changes during the closest approach of the storm to the experimental sites. Hodograph analysis revealed that inertia gravity waves(IGWs) associated with the cyclone changed their directions from northeast(control time) to northwest following the path of the cyclone. The momentum flux of IGWs and short-period gravity waves(1–8 h) enhanced prior to, and during, the passage of the storm(±0.05 m2s-2and ±0.3 m2s-2, respectively), compared to the flux after its passage. The corresponding body forces underwent similar changes, with values ranging between ±2–4m s-1d-1and ±12–15 m s-1d-1. The turbulence refractivity structure constant(C2n) showed large values below 10 km before the passage of the cyclone when humidity in the region was very high. Turbulence and humidity reduced during the passage of the storm when a turbulent layer at ～17 km became more intense. Turbulence in the lower troposphere and near the tropopause became weak after the passage of the cyclone.     

Mapping local regression for spatial object-pairs

Local regression methods such as geographically weighted regression (GWR) can provide specific information about individual locations (or places) in spatial analysis that is useful for mapping nonstationary covariate relationships. However, the distance-based weighting schemes used in GWR are only adaptable for spatial objects that are point or area features. In particular, spatial object-pairs pose a challenge for local analysis because they have a linear dimensionality rather than a point dimensionality. This paper proposes using an alternative local regression model – quantile regression (QR) – for investigating the stationarity of regression parameters with respect to these linear features as well as facilitating the visualization of the results. An empirical example of a gravity model analysis of trade patterns within Europe is used to illustrate the utility of the proposed method.     

卫星重力梯度数据重力异常的精度分析

针对GOCE卫星确定的地球重力场模型精度的不确定性,对比分析GOCE位模型与多个不同重力场模型确定的重力异常,并将其分别与船测重力数据、南极航空重力数据、北极重力数据以及美国和中国台湾地面重力数据比较研究。结果表明:GOCE位模型的内符合精度最高,与地面重力观测数据符合最优;与船测以及航空重力测量符合相对较差、精度较低。研究表明,在一定精度前提下,GOCE卫星确定的重力数据可用于无人区,从而提高重力观测数据的覆盖率。     

辽宁省城市竞争力重心时空迁移分析

针对辽宁省14个城市竞争力的发展特点和时空迁移变化规律的问题,该文借助于城市竞争力评价指标体系,得到了辽宁省14年来14个地级市的城市竞争力水平,基于区域重心模型,得到2001—2014年城市各项竞争力重心的动态迁移轨迹,并对其进行对比分析。结果表明:辽宁省14个城市的竞争力水平不均衡,城市综合实力差异明显;辽宁省14个城市的经济发展竞争力重心和环境发展竞争力重心呈现向东北方向偏移的趋势,社会发展竞争力重心呈现出向南发展的趋势,社会发展水平滞后于经济和环境发展水平;城市竞争力重心迁移是一个时期城市群发展影响因素的具体体现,社会发展需要同经济发展、环境发展协调进行,才能提升城市综合竞争实力。