A Quantitative Method for Active Fault Migration Distance Assessment on both Sides of Mid-Ocean Ridges—Based on Multi-Beam Data

Fracture-fissure systems found at mid-ocean ridges are dominating conduits for the circulation of metallogenic fluid. Ascertaining the distribution area of active faults on both sides of mid-ocean ridges will provide a useful tool in the search for potential hydrothermal vents, thus guiding the exploration of modern seafloor sulfides. Considering the Mid-Atlantic Ridge 20°N–24°N (NMAR) and North Chile Rise (NCR) as examples, fault elements such as Fault Spacing (?S) and Fault Heave (?X) can be identified and quantitatively measured. The methods used include Fourier filtering of the multi-beam bathymetry data, in combination with measurements of the topographic slope, curvature, and slope aspect patterns. According to the Sequential Faulting Model of mid-ocean ridges, the maximal migration distance of an active fault on either side of mid-ocean ridges—that is, the distribution range of active faults—can be measured. Results show that the maximal migration distance of active faults at the NMAR is 0.76–1.01 km (the distance is larger at the center than at the ends of this segment), and at the NCR, the distribution range of active faults is 0.38–1.6 km. The migration distance of active faults on the two study areas is positively related to the axial variation of magma supply. In the NCR study area, where there is an abundant magma input, the number of faults within a certain distance is mainly affected by the variation of lithospheric thickness. Here a large range of faulting clearly corresponds to a high proportion of magmatism to seafloor spreading near mid-ocean ridges (M) value, and in the study area of the NMAR, there is insufficient magmatism, and the number of faults may be controlled by both lithospheric thickness and magma supply, leading to a less obvious positive correlation between the distribution range of active faults and M.     

顾及空间自相关特征的机器学习水深反演方法研究

基于多光谱影像的水深反演方法是获取近岸水深信息的高效手段,然而反演精度低一直是制约其广泛应用的瓶颈。本文聚焦于实测水深与多光谱数据自身的空间自相关特性,提出在机器学习框架下将学习样本的空间自相关特征与统计互相关特征相结合,以提高水深反演精度。西沙北岛海域的实验结果表明：在实测数据量较小的情况下,相比传统机器学习,顾及自相关特征的新方法可获得18%的精度提升;而当实测数据量充足时,精度提升可达到27%。结果表明,将数据源的空间自相关特征融入机器学习算法中,可显著提升多光谱水深反演结果的精确性,进而为浅海海洋研究提供有效数据支撑。     

GNSS PPP/INS紧组合模式下的远海无验潮水深测量

为实现高精度远海水深测量潮位改正,基于GNSS/INS组合系统开展了远海多波束无验潮水深测量方法研究,并给出了无验潮水深测量基本原理及实施技术流程。结合GNSS/INS组合形式及滤波原理,分别探讨了在GNSS有效和失效状态下PPP/INS松组合与紧组合的性能差异。以PPP/INS紧组合解算结果为基础进行无验潮水深测量改正,并与传统预报潮位改正方法进行了对比,经试验验证,基于PPP/INS紧组合模式下的远海无验潮水深测量准确度可达0.14 m,并有效消除了动态吃水影响,在典型水深断面处的水深测量准确度明显优于预报潮位改正模式。     

应用重力地质方法反演皇帝海山的海底地形

论述了采用重力地质方法(GGM)反演海底地形的基本原理,并使用该方法计算了皇帝海山南部的海底地形模型,与现有的海深模型和船测海深数据相比,其精度略高于ETOPO2模型。与经典方法相比,GGM方法不需引入先验模型,不必考虑海底的均衡状况,模型简单,易于计算。     

A bathymetric overview of the Mariana forearc

Bathymetric data at a 200-m contour interval for the entire Mariana forearc, from south of 13°N to 25°N, permits the first comprehensive overview of this feature. The Mariana forearc represents a sediment-starved end-member. The forearc in its southern and central sections is divisible into a structurally complex eastern province and a less-deformed western province. Despite the absence of an accretionary complex the Mariana forearc has a well-defined outer-arc high; this probably results from a greater concentration of low-density serpentinized mantle lithosphere beneath the outer forearc relative to the inner forearc. This serpentinization gradient is coupled with differing deformational styles of thinner and more brittle lithosphere beneath the outer forearc compared to thicker and more ductile lithosphere beneath the inner forearc. The bathymetric data also support models calling for extension along-strike of the forearc, reflecting an increase in arc length accompanying the crescent-shaped opening of the Mariana Trough back-arc basin. Both northeast and northwest ridges and grabens can be identified, with the latter restricted to the southern part of the forearc and the former widely distributed in the central and northern forearc. Northeast-oriented extensional structures are supplanted northward by long, linear northwest-trending structures that are interpreted as left-lateral strike–slip faults. These variations in deformation along-strike of the forearc manifest a transition from nearly orthogonal convergence in the south to highly oblique convergence in the north.