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多波束资料在胶州湾口海底节理构造研究中的应用

利用2004年5月在青岛胶州湾口获得的高分辨率多波束资料(水平分辨率0.5m×1m,垂向分辨率0.2m),研究了该区海底节理构造及其分布规律,揭示青岛胶州湾团岛至薛家岛的研究区域中存在大量线性微地形,在海底地形图上表现为2组相交的“X”型线性阴影(一组为NE向,另一组为NW向),把整个海底切割成菱形格状。结合侧扫声纳探测等资料分析,认为这种线性微地形可能代表了海底出露的节理(裂隙)微构造。     

Computer simulation of multibeam echo sounding over rough seafloor

A computer code that simulates multibeam echo‐sounding over realistic (three‐dimensional) bathymetry was used to compare available sounding systems. Two‐dimensional modeling dealt with the resolution of seafloor bathymetry and with the effect of postprocessing algorithms for some typical multibeam systems. The 2‐D bathymetric inputs were idealized bottom features. Three‐dimensional modeling dealt with the gross character of the seafloor, as detected by echo‐sounding systems. The 3‐D bathymetric inputs were realizations of terrain generated by a stochastic model of seafloor roughness. Three‐dimensional modeling indicated that the sounding system may slightly shift the location of peaks within the beam footprint. In addition, the simulated measurements were more sensitive to low‐wavenumber features (i.e., large‐scale roughness) than to high‐wavenumber features (i.e., small‐scale roughness). Resolution gradually decreased with increasing distance from centerline, due to the increasing footprint size of beams at increasing angular distance from the vertical. Lineated terrain was also smoothed by simulated echo‐sounding; lineations may indeed remain undetected if sounding system parameters are not properly selected. Inversion of the simulated measurements indicated that echo‐sounding measurements are dependent not only on the characteristics of the sounding system itself, but on other factors such as the character of the roughness and the orientation of the survey relative to the strike of lineations. The modeling technique provides a way to quantify the system response of a multibeam echo‐sounding system. This work resulted in recommendations as to the most appropriate system for an application in an area of rough bathymetry, and it led to the establishment of criteria for comparing multibeam systems in future applications.     

A generic swath‐mapping data format

There is a pressing need for standardization of data derived from bathy‐metric swath‐mapping systems. Currently several dozen multibeam and sidescan sonar data formats exist within the oceanographic community, and more can be expected as new systems are developed. Without some standardization of swath‐mapping data formats, the capability for use and integration of data from different systems will be severely compromised.

This paper presents a strategy for organizing swath bathymetry data in a logical modular fashion that will allow data from all current swath bathymetric sonar systems to be stored and accessed in a common fashion. We have chosen the approach of defining compact efficient modules for each logically independent portion of a data record and storing it in a manner that is portable between diverse computer architectures and operating systems. This approach is extensible to accommodate new types of data. Although specifically developed for swath bathymetry, this format is also capable of supporting digital sidescan data and other types of swath data.     

障碍物探测方法探讨

介绍了侧扫声纳、多波束测深系统、磁力仪的工作原理,提出了障碍物探测的相关技术要求。实例分析了综合利用侧扫声纳、多波束进行沉船探测的方法,结合侧扫声图和多波束水深探明障碍物的精确位置,测得最浅点水深,全面获得障碍物信息,大大提高了探测质量。对铁磁性小目标探测能力进行评估,并用实例加以分析和佐证。     

接收机自主完好性监测算法及其性能分析

完好性是卫星导航系统的重要性能参数,接收机自主完好性监测作为用户端的完好性监测方法具有低成本、实施方便的优势。基于统计理论,给出RAIM算法统计检测量的设计方法,推导了阈值的确定方法及RAIM可用性判定方法。对一天中2880个采样时刻的RAIM性能进行仿真分析,结果表明,RAIM算法对于固定伪距误差的故障和慢变故障有良好的监测效果,排除故障星之后的定位误差可以保持在正常的水平。     

C3D测深侧扫声纳探测系统综述

对C3D测深侧扫声纳系统的构成、工作原理、性能、优点、应用等进行了介绍,对基于C3D构建水下探测系统和工程实践进行了研究,对C3D数据处理工具和方法进行了探讨,对C3D的优势、不足和应用前景进行了总结。实测表明,C3D是一款性能优越能够满足多种水下工程需要的声纳探测系统。     

汶川M_S 8.0地震:龙门山断裂两侧地壳各向异性的初步研究

利用中国地震局地质研究所地震动力学国家重点实验室在川西地区布设的大规模密集流动宽频带地震台阵记录的远震P波波形数据,分别采用波形互相关和加权叠加方法研究了地壳各向异性。作为初步结果,得到了龙门山断裂两侧4个宽频带流动台站的接收函数莫霍面Ps转换震相快波方向和分裂时间延迟。结果表明:1)波形互相关方法总体上优于方位加权叠加方法,它不但可以给出快波方位,而且可以给出快慢波的时间延迟;方位加权叠加方法测量结果存在不确定性,其原因在于难以确定介质各向异性对称轴的方位;同时采用上述2种不同方法研究地壳各向异性参数有助于判断测量结果的可靠性;2)四川盆地内快波偏振方位基本一致,表明四川盆地地壳整体性较好,横向非均匀变形较弱;3)以汶川地震主震的震中区为界,松潘-甘孜地块北侧快波偏振方位与龙门山断裂近于平行,表明在四川盆地坚硬地壳的阻挡作用下,龙门山断裂附近松潘-甘孜地块北侧可能存在中下地壳软弱物质沿断层向NE方向的扩张变形,而其南侧处于正向挤压的状态。该结果有助于解释汶川MS8.0地震的单侧破裂过程及其余震发育的特征     

利用接收函数研究延边地震台下方地壳结构

收集整理2007年以来延边地震台记录的113个远震数字波形资料,采用远震接收函数反演延边地震台下方地壳结构,运用H-Kappa叠加方法,计算得到台站下方地壳厚度和泊松比.采用全球平均地壳模型作为初始模型,反演台站下方0-100 km的S波速结构.反演结果表明,延边地震台下方地壳厚度为30.8 km,波速比为1.84,泊松比较高,为0.29.在台站下方15-20 km及25-30 km处存在低速层.