大地水准面高的计算及其在海底地形反演中的应用     

范雕  李姗姗  苏明晓  孟书宇  邢志斌  张驰  冯进凯 《海洋技术学报》2019,38(5)

为充分挖掘海洋重力数据在反演海底地形中的应用潜力,尝试探索利用大地水准面高反演海底地形的技术途径,并以夏威夷—皇帝海山链拐点所在海区作为反演试验区进行验证。首先采用Belikov列推法计算伴随(缔和)勒让德函数,利用EIGEN-6C4地球重力场模型解算获取了分辨率为1'的大地水准面高格网数值模型;然后通过综合分析反演比例函数和转换函数特点、研究海区大地水准面高与海底地形的相干特性以及大地水准面高本身尺度特征,获得了利用大地水准面高反演海底地形的频段范围;最终以试验海区大地水准面高为数据输入,构建了相应的海底地形模型(BNT模型),并与ETOPO1等海深模型进行比对分析。试验结果表明:BNT模型检核差值在一倍均方差范围检核点数量占比70.60%,相比正态分布更加集中;BNT模型检核精度低于ETOPO1等海深模型;海深模型检核精度随着水深增加不断提升,水深小于1 000 m时,海深模型相对误差出现较大发散现象;计算海域ETOPO1模型精度最高,GEBCO模型和DTU10模型检核精度相当。  相似文献   

压裂微震数据初至拾取的时频谱熵法     

田雅男  王环宇  王鑫  黄佳俊  章强 《吉林大学学报(地球科学版)》2020,50(4):1219-1227

在油气田开发过程中，微震监测是获得水力压裂引起裂缝分布的一种较为有效的方法。微震的定位成像与裂缝解释需要利用有效微震信号位置，而微震信号具有低信噪比的特点，传统信号拾取方法无法有效实现较低信噪比条件下初至时刻的准确拾取。本文提出一种基于时频谱熵的初至拾取新方法，该方法首先通过S变换获取含噪信号的时频谱；然后对谱内各个采样点沿频率方向进行分帧操作，并计算每帧频段内的近似负熵值，以最小近似负熵值作为该谱点的负熵值；最后沿时间方向比较各谱点的负熵值，最小值对应的时刻即为初至时刻。本文利用不同信噪比的合成地震数据对该方法进行效果验证，并与长短时窗能量比（STA/LTA）法进行拾取结果对比，结果表明：信噪比在-5 dB时，两种方法拾取效果都很好；信噪比在-10 dB时，时频谱熵法拾取效果更好。时频谱熵法更适合低信噪比情况下的信号初至拾取。  相似文献   

一种优化的频率域三维声波有限差分模拟方法   总被引：1，自引：1，他引：0       下载免费PDF全文

范娜  成景旺  秦雷  赵连锋  谢小碧  姚振兴 《地球物理学报》2018,61(3):1095-1108

为提高频率域有限差分（FD，finite-difference）正演模拟技术的计算精度和效率，基于旋转坐标系统的优化差分格式被广泛应用，但是只应用于正方形网格的情况.基于平均导数法（ADM）的优化差分格式，应用于正方形和长方形网格模拟.这些频率域有限差分算子，各自具有不同的差分格式和对应的优化系数求解表达式.本文基于三维声波方程发展了一种新的优化方法，只要给定FD模板形式，可直接构造频散方程，求取FD模板上各节点的优化系数.此方法的优点在于频率域FD算子的优化系数对应各个节点，可扩展优化其他格式.运用此优化方法，计算得到了不同空间采样间距比情况下27点和7点格式的优化系数.数值实验表明，优化27点格式与ADM 27点格式具有相同的精度，优化7点格式比经典的7点格式具有更小的数值频散.  相似文献   

天津港“8·12”爆炸事件记录波形分析          下载免费PDF全文

王晨辰  张盛中  杨晓瑜  张冰  李世鑫  刘敏 《地震工程学报》2018,40(1):130-138

利用天津地震台网23个短周期地震仪记录到的2015年8月12日天津港爆炸事件波形数据,对事件进行初步分析和研究。分别使用能量包络线法和波形匹配法,共识别出4次爆炸事件,并结合波形互相关的主事件定位法对爆炸事件进行定位。分析结果表明:第一次爆炸发生的时间为2015年8月12日23时34分4秒,1.77s后发生了规模更大的二号爆炸事件;34.11s后又发生了最强的三号爆炸事件;86.33s再一次发生了能量较弱的四号爆炸事件,其中二号与三号爆炸事件相距65~70m,二号与四号事件相距160~170m。此外,通过选用爆破、矿塌、核爆和天然地震等不同类型事件的波形数据,从时间域和频率域分别对这些事件进行对比分析,发现其震相特征表现出明显差异。  相似文献   

Feasibility of signal enhancement with multiple grounded‐wire sources for a frequency‐domain electromagnetic survey          下载免费PDF全文

Haigen Zhou  Yao Yao  Changsheng Liu  Jun Lin  Lili Kang  Gang Li  Xinsen Zeng 《Geophysical Prospecting》2018,66(4):818-832

Frequency‐domain electromagnetic methods with a grounded‐wire source are powerful tools in geophysical exploration. However, the signal may be too weak to guarantee the quality of survey data in complex electromagnetic environments, especially when the receiver is located in the air for the newly developed grounded‐source airborne frequency‐domain electromagnetic method. In this paper, a signal enhancement method with multiple sources is proposed to solve this problem. To evaluate the signal enhancement effect, we compared the signals generated by a single source and multiple sources with equal electric moment. The signal differences caused by synchronisation error and separation distance between source elements were analysed, and the methods to achieve maximum signal were introduced. Besides, we discussed the interaction between adjacent source elements to ensure the system safety, including the changes in output current and the safe distance between two sources using a dual‐source model. Lastly, a comprehensive field experiment was designed and conducted to test the multiple‐source method. The data processing results are comparable for single and dual sources, and the signal‐to‐noise ratio of dual source is higher in the field test. The subsurface resistivity structure at the test site is consistent with the previous controlled‐source audio‐frequency magnetotellurics method. These results show that signal enhancement with multiple sources is feasible. This study provides guidance to the application of multiple sources in field surveys when the survey environment is complex and rigorous.  相似文献   

Experimental study on wide-shallow composite bucket foundation for offshore wind turbine under cyclic loading     

Xuyue Wang  Hongyan Ding  Yonggang Liu 《Marine Georesources & Geotechnology》2019,37(1):1-13

As an appropriate type of foundation for offshore wind turbines (OWTs), wide-shallow composite bucket foundation (WSCBF) is cost-competitive, and it has a unique and special substructure that comprises seven internal rooms arranged in a honeycomb-like structure. In this study, the cyclic behavior of WSCBF for OWTs embedded in saturated clay was investigated using a large-scale model subjected to lateral cyclic loading. The responses of foundation under constant- and various-amplitude cyclic loadings were recorded in terms of displacements, rotations, and bending moments. The variations in stiffness and damping were obtained, and a collaborative bearing mechanical model between the bucket and soil was considered, which was beneficial for improving the stiffness of the whole structure. Accumulative deformation was found to have little effect on the bearing capacity of the foundation. Dynamic analysis in frequency domain was further performed on both moment and rotation data, and the complex, frequency-dependent impedance was also studied.  相似文献   

具有低频超宽衰减域的部分埋入式表面波屏障     

秦凯强  刘泽  于桂兰 《地震工程与工程振动》2020,(2):187-194

针对低频Rayleigh表面波,设计了部分埋入式工字形截面周期波屏障。利用有限元方法计算了结构的频散曲线,分析了带隙的形成机理,讨论了屏障埋入土体深度和截面参数对带隙的影响,在此基础上设计了具有低频超宽衰减域的梯度及分段梯度波屏障并计算了其传输谱。结果表明:周期波屏障存在较宽带隙,板埋入深度和端部尺寸是影响带隙的关键参数,通过参数调节可实现不同频段Rayleigh波的调控。工字形变截面波屏障比等截面具有更优越的隔震性能且节省材料。梯度及分段梯度波屏障显著拓宽了衰减域的频率范围,对1.5~20 Hz范围内的Rayleigh表面波实现了全覆盖,用小尺寸控制了大波长。  相似文献   

地基干涉雷达IBIS-S桥跨结构振动变形测量与模态分析   总被引：2，自引：0，他引：2  

王鹏  邢诚  项霞 《测绘通报》2019,(10):35-39

地基雷达干涉测量技术能够以较高的时空采样频率获取线性结构目标整体瞬时变形状态。本文将该技术引入大型桥梁桥跨结构的振动变形测量与模态分析中。对动静载试验过程中的武汉二七长江大桥东岸桥跨结构开展连续变形监测，利用频域分解法计算桥跨结构的自振频率、阻尼比和模态振型。计算结果表明，地基干涉雷达干涉测量技术能够快速探测桥跨结构竖弯模态，特别适用于灾后大型线形结构健康状态的应急检测。  相似文献   

小波检验方法在国内业务模式中的最新应用研究进展     

徐同  李佳 《沙漠与绿洲气象(新疆气象)》2015,9(6):1-10

本文主要介绍小波检验方法在国内区域业务模式中的最新应用研究进展,该方法被应用于模式降水预报的个例检验和统计检验,并针对两种解决二元域限制问题的技术方案进行阐述和讨论。结果表明：D8小波可以提供一种从不同降水率阈值和空间尺度对模式定量降水预报进行评估的方案,该方案首先对预报场和分析场进行阈值获得二进制误差场,再对二进制误差场进行尺度分解,从而可以评估模式在各个降水率阈值和空间尺度上的预报技巧和偏差。统计检验结果显示模式对较大尺度降水事件表现出较高的预报技巧评分,较小尺度降水事件和强降水的预报技巧评分相对较低,并且总体上呈现出预报降水事件多于观测降水事件的特征。Padding方案和Tiling方案对应的模式统计检验结果并无明显差异,由于后者不对原始降水场做任何改变,因此是一种更为稳健和可靠的方案。  相似文献   

Regional Distribution and Prospects of Potash in China   总被引：4，自引：0，他引：4  

ZHENG Mianping  an  ZHENG Mianping  YUAN Heran  LIU Xifang  CHEN Wenxi  LI Jinsuo 《《地质学报》英文版》2011,85(1):17-50

China was formed by amalgamation of several small continental blocks (cratons), micro, blocks and orogenic belts in different paleoclimatic settings. It may be correlated with other continental blocks but has its own specific characteristics; therefore the tectonic environments of China’s marine and continental saline basins and salt, and potash, forming environment have some specific characteristics: multiple phases of salt formation, difference in salt, forming ages, migration and concentration of salt, forming processes and diversity of component materials, as well as small sizes of marine saline basins and great changes of saline basins in the late stage and occurrence of abundant liquid mineral resources. The nature of the tectonic basement exerted a key controlling effect on the formation of potash basins. The stable tectonic region was favorable for potash concentration in a quasi, stable region, and quasi, and the quasi-stable region was favorable for salt concentration and potash formation in a local stable tectonic region. Most China’s major ancient saline basins occur in “quasi, cratons (continental block)”; especially all the marine saline basins occur in continental blocks with the Precambrian basement. These regions are the key ones for potash search. Most relatively large, scale soluble salt deposits are developed in relatively stable continental nuclei. According to the characteristics of the tectonic domains where China’s salt, forming basins are located, the North China, Yangtze and Tarim, Qaidam salt minerogenetic domains and the northern Qiangtang, western Yunnan salt minerogenetic belt may be distinguished. Their salt and potash prospects will be discussed separately.  相似文献