基于纵横波解耦的三维弹性波逆时偏移          下载免费PDF全文

周熙焱  常旭  王一博  姚振兴 《地球物理学报》2018,61(3):1038-1052

纵横波波场分离是弹性波偏移方法的必要条件,通过纵横波成像的差异可以获取更多地下介质的信息.目前所用的纵横波波场分离方法多采用Helmholtz分解,这样得到的波场不仅物理意义发生了变化,振幅和相位也会发生改变.本文采用纵横波解耦的弹性波方程,将其应用于三维介质,对比分析了纵横波解耦方法相对传统Helmholtz分解方法在相位、振幅上的优势.将该解耦的波场分离方法应用于弹性波逆时偏移,能得到相位、振幅和物理意义不受改变的偏移结果.但是该解耦方法分离得到的纵横波波场均为矢量场,将该波场分离方法用于弹性波逆时偏移,还需要解决矢量场如何得到标量成像结果的问题.本文引入了Poynting矢量,通过Poynting矢量对矢量波场进行标量化,这样就能得到保振幅、相位,且无极性反转的标量PP和PS成像结果.同时针对S波Poynting矢量求取不准确的问题,采用拟S波应力场和S波速度场得到了更加准确的S波Poynting矢量.理论计算证明了本文采用的3D波场解耦的矢量波场分离方法的正确性和引入Poynting矢量对矢量波场进行标量成像的有效性.  相似文献   

龙门山断裂带北段南坝地区上地壳S波分裂特征   总被引：1，自引：1，他引：0       下载免费PDF全文

郑拓  丁志峰  常利军  宁杰远  张辉  王兴臣 《地球物理学报》2018,61(5):2054-2065

基于汶川科钻4号井孔（WFSD-4）附近的较小尺度的南坝微震台阵以及较大尺度的川西流动台站和区域台网的固定台站记录到的近震波形资料,通过横波窗内的S波分裂计算,分析了龙门山断裂带北段南坝地区的上地壳介质各向异性特征,并对区域应力场及构造特征展开讨论.S波分裂计算的结果显示研究区快波偏振方向主要表现为NE-NEE向,与北川断裂的走向一致,也与区域主压应力方向一致.小尺度密集分布的南坝微震台阵的计算结果进一步显示,靠近北川断裂的台站,其快波偏振方向与断裂走向一致,而距北川断裂较远的西北部台站的快波偏振方向与断裂走向不一致,反映了上地壳各向异性特征与地表的活动断裂结构密切相关.从南坝微震台阵的归一化时间延迟随时间的变化情况可以发现,在一个震中位于台阵布设范围内的地震事件发生前后,时间延迟有明显的变化,表明时间延迟随时间变化较为敏感,地震的能量影响了介质的性质.对比龙门山断裂带中段的科钻3号井孔周边地区的S波分裂计算结果,归一化时间延迟与本文结果一致,表明龙门山断裂带中段和北段的上地壳介质各向异性强度基本相同.  相似文献   

云南地区地壳上地幔三维S波速度与径向各向异性结构研究   总被引：2，自引：0，他引：2       下载免费PDF全文

陈浩朋  李志伟  储日升  谢军  崇加军  叶庆东 《地球物理学报》2018,61(8):3219-3236

云南地区地处青藏高原东南缘,一直是地球科学研究的热点地区.目前,一些热点问题,如云南地区是否存在中下地壳低速流及其空间分布,仍有一定的争议.通过建立云南地区精细的地壳上地幔速度与各向异性结构,可为深入认识上述问题提供重要信息.本文利用天然地震波形记录,采用双台法提取了12~60 s周期的Rayleigh和Love波相速度频散,并进一步反演获得了云南地区10~100 km的三维地壳上地幔SV和SH波速度及径向各向异性结构.结果表明：S波速度与径向各向异性结构在横向和垂向均存在显著变化.在20~30 km深度,存在两个低速条带,且条带内呈现出正径向各向异性（V_SH>V_SV）特征,暗示了中下地壳低速物质的水平向运动.在80~100 km深度,云南西南和东南部显示为低速异常和正径向各向异性特征,暗示了软流圈物质的水平流动.在云南北部的丽江、攀枝花和昭通地区,岩石圈地幔中则存在明显的负径向各向异性（V_SH<V_SV）,可能反映了地幔物质的上涌痕迹.历史强震多发生在地壳低速区域或高低速过渡带,且地震附近的径向各向异性为负或者较弱.一些地震震源下方存在低速层,地壳低速层可能会促进强震发生.  相似文献   

JOINT INVERSION OF AMBIENT NOISE AND SURFACE WAVE FOR S-WAVE VELOCITY OF THE CRUST AND UPPERMOST MANTLE BENEATH WEIHE BASIN AND ITS ADJACENT AREA          下载免费PDF全文

FENG Hong-wu  YAN Wen-hua  YAN Shan  GUO Ying-xia  HUI Shao-xing  CHANG Cheng 《地震地质》2019,41(5):1185-1205

The Weihe Basin is the main component of the extrusion and escape shear zone between the ancient North China craton block in Ordos and the ancient Yangtze platform in Sichuan Basin, and carries the dynamic transmission from the main power source of the Qinghai-Tibet Block in the west to the North China and South China regions in the east. The basin itself plays multi roles in the east-west and north-south tectonic movement, and is an excellent site for studying the structural interlacing, dynamic transformation and transmission. At the same time, Weihe Basin is also a famous strong earthquake zone in China. Historically, there was a strong earthquake of magnitude 8 1/4 occurring in Huaxian County in 1556, causing huge casualties and property losses. In view of the special geological structures and the characteristics of modern seismicity activities in the Weihe fault-depression zone, it is necessary to carry out fine three-dimensional velocity structure detection in the deep part of Weihe Basin and its adjacent areas, so as to study the relationship between velocity structure and geological structural units and their evolution process, as well as the deep medium environment where earth￣quakes develop and occur. We investigate the S-wave velocity structure beneath Weihe Basin and its adjacent regions based on continuous background noise data and teleseismic data recorded by 257 broadband stations in Shaanxi Province and its adjacent regions and China Seismological Science Array Exploration Project, and by adopting seismic surface wave inter-station method and background noise cross-correlation method, a total of 10 049 fundamental-mode Rayleigh surface wave phase velocity dispersion curves in the periods of 5~70s are obtained. Firstly, using the average dispersion curve in this study area, we obtain the one-dimensional average S-wave velocity structure model of the study area, and then we apply the ray-tracing surface-wave-dispersion direct inversion method to obtain the S-wave velocity structure of the crust and uppermost mantle (3~80km) beneath Weihe Basin and its adjacent regions. The test results of a 1°×1° grid checker board show that the recovery is good, except for the areas east of 111° and south of 32° of the study area, where there is almost no resolution. The imaging results show that the velocity structure beneath each tectonic unit in the study area has a certain distribution rule, and there is a good correlation between surface geological structure and deep velocity structure. Based on the analysis of velocity slices at different depths and S-wave velocity structures of three profiles, and combined with existing geological structures, geophysics and other deep exploration research results, we obtain the following knowledge and conclusions:1)The thick sedimentary layer covering the top of Weihe Basin is the cause of low velocity anomaly in its shallow crust, the middle and upper crust of the basin are of low velocity structure, and the low-velocity zone extends about 25km, the Moho interface uplifts abruptly relative to both the Ordos Block and the Qinling orogenic belt on opposite sides, and high-speed materials from the upper mantle intrude into the lower crust, which may be related to the underplating of mafic-ultramafic materials from the upper mantle in Mesozoic-Cenozoic period; 2)The south Ordos Block is not a homogeneous whole, the low-velocity structure of the shallow crust in southern Ordos Block is thin in east and thick in west, which may be related to the overall tilting of the Ordos Basin since the Phanerozoic, as well as the differential uplift and strong and uneven denudation of the Ordos Block since the Late Cretaceous. The crustal structure of the south Ordos Block is relatively simple and homogeneous. There is no significant low-velocity structure in the curst of the block, which shows that the low-velocity structure in the crust does not penetrate the whole Ordos block. We speculate that the southern Ordos Block still maintains the stable craton property, and has not been reformed significantly so far; 3)The variation characteristics of deep structure of the Qinling orogenic belt reflect the deep crustal structure and tectonic deformation characteristics of the orogenic belt which are strongly reformed by land-land collision and suture between North China plate and Yangtze plate, intracontinental orogeny, uplift of Qinghai-Tibet Plateau and its northeastern expansion since the Late Hercynian-Indosinian period. The deep structure beneath the eastern and western Qinling orogenic belt is different and has the characteristics of segmentation. The low-velocity anomaly at the bottom of the lower crust of the orogenic belt may be affected by tectonic activities such as uplift and outward extension of the NE Tibetan plateau, and the analysis considers that there is little possibility of the existence of lower crustal circulation channel for the eastward flowing of Tibetan plateau materials in the Qinling orogenic belt. However, since the maximum depth from the inversion of this paper is 80km, which is located at the top of the upper mantle, our results cannot prove that there exists a mantle flow channel for the eastward flow of Tibetan plateau material beneath the Qinling orogenic belt.  相似文献   

唐山地区震源模型及局部场地效应     

景立平  金星  松波孝治 《地震工程与工程振动》1998,18(4):23-29

本文利用唐山地区强震观测台网在过去几年中记录到的强震数据,采用震源,传播路径和局部场地效应分离方法和非线性曲线拟合技术,模拟了唐山地区的震源参数,计算了唐山地区的绝对局部场地效应。  相似文献   

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朱新运  魏红梅  黄世源 《大地测量与地球动力学》2009,29(6):133-138

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三峡库区上地壳横波速度结构   总被引：1，自引：0，他引：1       下载免费PDF全文

李小勇  朱培民  周强  彭松柏  刘江平  刘娇 《地球科学》2014,39(12):1842-1850

为了更好地了解三峡库区的稳定性, 利用三峡库区的流动宽频地震仪台阵于2011年4~5月期间观测的背景噪声数据, 采用互相关方法提取了瑞利面波的格林函数, 用多重滤波方法获得了瑞利面波的群速度频散曲线.利用走时层析成像方法获得了0.5~10.0 s周期的纯路径频散曲线, 进而反演获得了沿巴东-茅坪-土门方向的横波速度结构剖面, 揭示了三峡地区上地壳的速度变化情况.研究表明: (1)研究区地下速度结构与地质构造关系密切, 速度剖面上很好地反映了一个以黄陵背斜核部为中心的背斜构造; (2)九畹溪及其周边区域下方较快的速度变化可能与对应的区域断裂构造、地震活动性密切相关; (3)三斗坪地区上地壳表现为高速, 表明三峡坝区处于构造稳定区域.   相似文献   

东海平湖油气田流体识别方法与应用研究     

许风光  梁连喜  陈明  高伟义 《海洋地质译丛》2009,(1):94-99

平湖油气田位于东海陆架盆地西湖凹陷保傲斜坡平湖构造带中段，主要生产层是渐新世花港组油藏和始新世平湖组气藏。传统地质观点认为平湖组为主要气藏，但是实际生产中八角亭BX1井平湖组P11等气层有原油产出，给油气藏的开发带来一定挑战。准确地确定储层的流体性质，不仅对气藏开发方式选择和开发经济政策制定，而且对滚动勘探都具有重要意义。根据气、油和水物理性质之间的差异，利用非电测井信息，基于不同饱和流体岩石具有不同的横波时差、纵波时差、纵波等效弹性模量、流体密度、流体时差和流体声阻抗，结合其它测井手段，有效识别了平湖油气田AX9井、BX8井、BX1井和PX9井储层的流体性质。识别结果与实际生产状况基本一致，说明该方法在平湖油气田流体识别方面具有良好的应用效果。  相似文献   

基于散度和旋度纵横波分离方法的改进   总被引：3，自引：2，他引：1       下载免费PDF全文

李志远  梁光河  谷丙洛 《地球物理学报》2013,56(6):2012-2022

纵、横波的分离是多波多分量地震资料处理中很重要的一步,其分离结果直接影响到后续数据处理的质量.各向同性介质中纵波为无旋场,横波为无散场,因此可以在频率-波数域利用散度和旋度算子对地震记录进行纵、横波分离,但是此处理过程必须知道地表处的纵、横波速度.本文给出了一种估算地表纵、横波速度的方法,可以在纵、横波速度值未知的情况下,将其估算出来.针对弹性波场进行散度和旋度运算时,纵、横波的相位和振幅比发生改变的问题,本文给出了相位和纵、横波振幅比的校正方法.  相似文献   

用面波联合勘探技术探测浅部速度结构   总被引：3，自引：0，他引：3  

张维  何正勤  胡刚  李俊 《地球物理学进展》2013,28(4)

瑞雷面波勘探技术以其快速经济、受场地条件限制小等优点广泛应用于浅部横波速度结构探测.人工源面波勘探方法对浅部地层的探测精度高,但探测深度较浅;天然源面波勘探方法探测深度较深,但对浅部速度结构的探测精度不高.本文在夏垫和玉溪两地分别开展了人工源和天然源面波联合探测试验,尝试采用不同排列和相同排列两种方法,采集人工源和天然源面波信息,联合处理数据并提取频散曲线,反演得到浅部地层的横波速度结构.探测结果表明:人工源和天然源面波联合勘探,尤其是采用相同排列的方法,可以在几乎不增加常规面波勘探工作量的条件下,既能保证浅部地层的探测精度,又明显拓展探测深度,大大提升了面波勘探能力,有望在工程勘察领域中推广应用.  相似文献