Stretching correction for amplitude-preserving vector wavefield reverse-time migration     

《China Geology》2019,2(2):179-188

The migration of multi-wave seismic data is aimed at obtaining the P- and S-wave imaging results of the amplitude preserving. But the P- and S-wave stretching effect produced by the reverse time migration of the elastic wave equation will not only reduce the vertical resolution of the migration results and the amplitude preserving of the large reflection angle. In this paper, the reverse time migration technique of amplitude preserving vector wave-field separating is used. Based on the analysis of the stretch mechanism and the influencing factors of stretch magnitude, the paper gave the stretch correcting factors. Then, realize the stretch correction method at the time that after the reverse extrapolation and before the imaging by solving the problem which is how to calculate the P-wave and Ps-wave propagation directions of imaging points at different times. The stretch correction method can improve the vertical resolution and amplitude fidelity of the imaging results and provide high fidelity input data for seismic data interpretation and inversion.© 2019 China Geology Editorial Office.  相似文献   

提高任意广角波动方程计算效率及压制倏逝波干扰方法   总被引：1，自引：1，他引：0  

周辉  陈汉明  李绪宣  范廷恩 《地球物理学报》2014,57(4):1188-1198

任意广角波动方程（Arbitrarily Wide-angle Wave Equation，AWWE）是一种高精度的时空域单程波动方程，与其他时空域单程波方程相比，具有更大的成像倾角，因此是偏移成像的有力工具之一.本文改进了现有的AWWE有限差分计算方案，避免了原计算方案中对矩阵反复求逆的过程，同时减少了矩阵相乘的次数，显著地提高了AWWE数值计算的效率.数值实验证实，采用改进之后的计算方案，其计算结果与原方案完全一致.此外，本文采用了一种方法，在有倏逝波干扰的情况下，能在频率-波数（f-k）域区分出倏逝波与非倏逝波，为设计f-k滤波器提供合理的视速度门槛信息.偏移实验证实，在深度延拓时仅仅进行数次f-k滤波就能很好地抑制倏逝波干扰，提高偏移成像质量.  相似文献   

角度域剩余深度对剩余速度的敏感性分析          下载免费PDF全文

徐嘉亮  常旭  王一博 《地球物理学报》2015,58(8):2927-2934

本文针对地震勘探深度域偏移速度建模研究,利用角度域共成像点道集(ADCIGS)建立了以剩余速度为自变量,剩余深度为目标函数的关系式,及目标函数的梯度公式.利用导出的两个公式分别对剩余深度与剩余速度的关系进行了定量分析.通过理论分析和模型试算证明初始速度模型的误差具有方向敏感性,即正误差较负误差对速度建模迭代收敛更敏感.利用此结论进行深度域速度建模既可以提高计算效率也可以提高建模精度.  相似文献   

基于偏微分方程的模型光滑处理在偏移成像中的应用          下载免费PDF全文

韩复兴  孙建国  王坤 《地球物理学报》2018,61(11):4558-4567

本文针对射线类偏移成像当中的速度模型光滑处理问题，借鉴数字图像处理当中的偏微分方程法，基于能量泛函，应用变分方法导出基于速度模型的偏微分方程实现射线类偏移成像当中的速度模型的光滑处理.由于偏微分方程法具有线性叠加特性、模型解的唯一性和局部特征保持性，因此，应用该算法可以实现基于原始速度模型空间结构的模型光滑处理.通过在原始速度模型以及光滑处理后的速度模型上计算速度的空间分布以及地震波走时、射线路径可以得出，偏微分方程法对速度模型的光滑处理能够很好地保持原始模型的空间结构，偏移成像结果也证明了该方法的实用性.  相似文献   

匹配滤波方法研究2016年意大利中部MW6.0地震的余震迁移     

付裕  黄晖  徐鸣洁 《中国地震》2018,34(4):621-631

2016年8月24日意大利中部发生M_W6.0地震，2个月之后，震中附近相继发生M_W5.5、M_W5.9、M_W6.5地震。研究这几次较大地震间的相互触发作用及机制十分必要，然而在大地震之后传统地震目录通常缺失很多余震事件，缺失的余震事件包含着早期余震时空分布和迁移规律的信息，为完善余震目录本文利用匹配滤波方法对M_W6.0地震后80天内的连续数据进行余震检测，得到了数十倍于模板数量的新检测事件，检测事件与模板事件组成的新余震目录完备震级为1.0，提高了地震目录的完备性。依据新余震目录进行余震时空分布研究，结果显示M_W6.0、M_W5.9、M_W6.5地震的早期余震迁移规律不同。M_W6.0地震的早期余震沿着断裂走向同时朝两侧迁移；而M_W5.9、M_W6.5地震的早期余震向南、北迁移表示出不对称的特征。通过拟合余震迁移前端发现，M_W6.0、M_W5.5地震的早期余震朝着随后较大地震的方向迁移，且较符合lgt的特征，表明余震迁移可能与慢滑动有关。  相似文献   

Ageing,migration and familial support in rural China     

《Geoforum》2014

Accelerated by economic reforms, a large scale migration of younger workers from rural to urban China has taken place since the 1990s. This has separated many adult children from their ageing parents and imposed significant challenges on traditional patterns of familial support for rural older people. These challenges are augmented by the fact that in rural China the elderly have been deprived a state pension and other welfare provisions available to urban residents.Drawing upon qualitative data from a project on ageing in rural China, this article examines the agency of older people and their families in responding to geographical separation resulting from the migration of the economically active to the cities. Through 32 life history interviews with multiple generations of nine households in one rural village, this article sheds light on the resilience and flexibility of rural households which have experienced migration and highlights the webs of interdependence that feature in the daily strategies of householding. It shows how members of the household across different geographical locations worked together to build and maintain the collective welfare of the family. In particular, this article argues that it would be over simplistic to suggest that migration is always detrimental to the older generation who stay behind. Contrary to assumptions in some migration studies and ageing literature in China, it shows that it is the breakdown of the webs of interdependence and reciprocity rather than the event of migration that will have inevitable negative effects upon old age care for the seniors in the household. Further, while highlighting the significance of householding, this article reveals the internal dynamics within a household. It identifies the role of gender in daily householding and suggests that the caring, supportive and kin-keeping roles performed mainly by women played a critical role in ensuring social and physical reproduction across generations. The article finds that while daughters took over some responsibilities which were traditionally expected from their brothers and sisters-in-law in old age support, the persistence of gendered practices and traditions in rural villages allowed sons more symbolic status and material benefits.  相似文献   

主动源与被动源地震数据插值及联合数据成像   总被引：1，自引：1，他引：0       下载免费PDF全文

张盼  韩立国  刘强  张亚红  陈雪 《地球物理学报》2015,58(5):1754-1766

本文提出了两种情况下主动源数据和被动源数据的插值方法,并研究了两种数据在偏移成像中的互补效果.基于互相关法被动源数据重构原理,本文提出了结合多域迭代去噪技术的重构方法.提出了两种时间域主动源和被动源数据的插值方法,分别是共炮点域能量匹配插值和共检波点域最小平方匹配插值.然后对获得的主动源和被动源联合地震数据进行叠前深度偏移成像.在被动源活跃度不是很高的地区进行被动源地震勘探时,少量的主动源地震数据可以有效控制和补充被动源数据的成像效果.在稀疏炮点的主动源勘探中,有效利用被动源的信息能够在成像中增加更多的细节信息,提高成像质量.  相似文献   

Multi-scalar inequality: Structured mobility and the narrative construction of scale in translocal Cambodia     

《Geoforum》2017

Focusing on three neighbouring villages in Cambodia, this paper argues the need for a multi-scalar interpretation of the relationship between mobility and wealth. It analyses migrant livelihoods in both sender and receiving areas to show that single scale measurements of mobility are inappropriate in the context of translocal livelihoods because livelihoods enacted across multiple places may possess multiple values of scale and mobility, each co-existing within the same migrant lifeworld. In seeking an improved conception of these complexities, the paper has combined spatial and qualitative analysis of translocal livelihoods to highlight the linkages between mobility in multiple places. On this basis, it posits that the mobility of translocal livelihoods must be assessed at least three scales: the scale appropriate to the sending environment, the scale appropriate to the receiving environment, and the scale on which potential migrations are judged. Making use of this framework allows clear relationships to be observed between mobility and inequality in both the narratives and structures of the communities under investigation.  相似文献   

Generalized diffraction‐stack migration and filtering of coherent noise     

Ge Zhan  Wei Dai  Min Zhou  Yi Luo  Gerard T. Schuster 《Geophysical Prospecting》2014,62(3):427-442

We reformulate the equation of reverse‐time migration so that it can be interpreted as summing data along a series of hyperbola‐like curves, each one representing a different type of event such as a reflection or multiple. This is a generalization of the familiar diffraction‐stack migration algorithm where the migration image at a point is computed by the sum of trace amplitudes along an appropriate hyperbola‐like curve. Instead of summing along the curve associated with the primary reflection, the sum is over all scattering events and so this method is named generalized diffraction‐stack migration. This formulation leads to filters that can be applied to the generalized diffraction‐stack migration operator to mitigate coherent migration artefacts due to, e.g., crosstalk and aliasing. Results with both synthetic and field data show that generalized diffraction‐stack migration images have fewer artefacts than those computed by the standard reverse‐time migration algorithm. The main drawback is that generalized diffraction‐stack migration is much more memory intensive and I/O limited than the standard reverse‐time migration method.  相似文献   

Migrant pathways to resource access in Lampung’s political forest: Gender, citizenship and creative conjugality     

Rebecca Elmhirst 《Geoforum》2011,42(2):173-183

An important theme in studies of enclosure and resource access in Southeast Asian hinges on the concept of the ‘political forest’, a particular constellation of power constituted by ideas, practices and institutions that seek to regulate peoples’ access to resources, providing recognition and legitimacy to some, whilst excluding and criminalizing others. Whilst issues of class and ‘race’ underpin work in this vein, in Indonesia, much less attention has been directed towards the ways in which gender inheres in the regularisation of land and livelihood, and the ordering of upland spaces. Drawing on recent feminist and queer theorizing of the links between citizenship, recognition and hetero-normativity, and on analyses of the social relationships through which resource access is negotiated and realized, the paper presents a feminist political ecology of the gender dynamics inherent in the power plays of resource access as land-poor rural migrants negotiate a shifting landscape of enclosure in Lampung province. Through an analysis of three periods of resource governance and control in the province, the paper shows how the negotiation of resource access is simultaneously a process of self-regulation and subject-making that draws on particular ideas about family and conjugal partnership, inculcating gendered and hetero-normative ideologies of the “ideal citizen”. Through particular representational strategies - positionings - necessary to qualify for resource access, and through the material practices necessary to realize the benefits of resource access, conjugal partnership is reiterated and remade as an important social relationship through which resource access may be realised, for men as well as for women.  相似文献