深源与浅源气体震前异常变化的差异性

本文根据１９９３年６月至１９９４年１月滇西及其邻近地区数次中强以上地震前ＣＯ２，Ｎ２，Ａｒ，Ｒｎ等气体组分释放动态的观测结果，研究了气体的物质迁移对其前兆异常变化的影响，发现深，浅源气体的震前趋势性异常释放和短临突跳异常的发生时间具有明显的有序性，基本模式是源自深部的气体组分的震前异常变化总是上先于浅源气体，这种现象在强震发生前更为明显。作者认为，导致深一浅源气体异常变化有序发生的原因与气体物质迁     

多分量地震数据的成像技术

从水平叠加成像、叠前时间偏移以及叠前深度偏移三个方面总结了多分量地震成像技术的发展现状.在水平叠加成像方面,分析了转换波与纵波在道集抽取方面的差异,总结了常用的转换点计算公式,着重对比了由炮检坐标映射地下的转换点以及由地表的网格节点映射地下的反射点两种共转换点道集抽取方式各自的优缺点以及应用化程度.概述了各向同性与各向异性叠前时间偏移技术的基本原理,总结了多分量偏移技术发展以及配套软件的工业应用现状,并对最近发展的层匹配多分量偏移技术进行了介绍.最后,从射线理论以及波场延拓理论的角度总结了多分量叠前深度偏移的发展现状与存在的问题,介绍了标量偏移与矢量偏移的差异,并提出了深度域速度建模存在的问题.

     

The middle space of migration: A case study on brokerage and recruitment agencies in Nepal

Foreign employment has become a global phenomenon. With the increasing commercialisation and formalisation of transnational labour migration, recruitment agencies and agents have gained importance. The paper aims to contribute to a more differentiated understanding of the role and the practices of the main actors in the middle space of migration, the brokers in the recruitment process for transnational migration. Based on empirical material from Nepal, it argues that the detected negative reputation of labour brokers is only partially justified. Besides common bad practices and fraud cases, recruiters perform important roles for the facilitation of transnational mobility and present the necessary infrastructure for labour migration. They connect people and places, establish networks and can play an important role in making migration safer. Brokers are important facilitators in supporting alternative income strategies and new livelihood options of people. At the same time they are entrepreneurs in a competitive and risky economic field, confronted with multifaceted constraints. As long as the gap between the dreams of potential migrants and the reality of marginality in Nepal remains wide, labour brokers might persist as important middlemen for global work. Thus, migration brokerage is likely to remain big business.     

Combination of common-midpoint-refraction seismics with the generalized reciprocal method

A useful method for increasing the signal/noise ratio of refracted waves is Common-Midpoint (CMP)-refraction seismics. With this technique the shallow underground can be described in detail using all information (amplitude, frequency, phase characteristics) of the wavetrain following the first break (first-break phase). Thus, the layering can be determined and faults, weak zones, and clefts can be identified. This paper deals with the optimization of CMP-refraction seismics used in combination with the Generalized Reciprocal Method (GRM). Theoretical studies show a close relationship of both methods to the kinematics of wave propagation. Velocities and optimum offsets determined by the GRM can be used directly in the partial Radon transformation in CMP-refraction seismics. The integration of refracted waves leads to an increase in the signal/noise ratio but simultaneously the integration boundaries must be restricted to deal only with selective parts of the investigated refractor. The result of this process is an intercept-time section which can be converted directly to a depth section using standard refraction seismic techniques. Another possibility of depth conversion is the transformation of this intercept-time section to a `pseudo-zero-offset section', known from reflection seismics. Thus, zero-offset sections can be migrated using wave-equation techniques such as Kirchhoff migration.     

From outcrop and petrographic studies to basin-scale fluid flow modelling: The use of the Albanian natural laboratory for carbonate reservoir characterisation

The Albanian fold-and-thrust belt and the Peri-Adriatic Depression are well documented by means of seismic reflection profiles, GPS reference points, potential data, wells and outcrops. The continuous Oligocene to Plio-Quaternary sedimentary records help to constrain both the burial history of Mesozoic carbonate reservoirs, the timing of their deformation, and the coupled fluid flow and diagenetic scenarios.Since the mid-90s, the Albanian foothills were used as a natural laboratory to develop a new integrated methodology and work flow for the study of sub-thrust reservoir evolution, and to validate on real case studies the use of basin modelling tools as well as the application of new analytical methods for the study petroleum systems in tectonically complex areas.The integration of the interactions between petrographic and microtectonic studies, kinematic, thermal and fluid flow basin modelling, is described in detail. The fracturing of the reservoir intervals has a pre-folding origin in the Albanides and relates to the regional flexuring in the foreland. The first recorded cement has a meteoric origin, implying downward migration and the development of an earlier forebulge in the Ionian Basin. This fluid, which precipitates at a maximum depth of 1.5 km, is highly enriched in strontium, attesting for important fluid–rock interaction with the Triassic evaporites, located in diapirs. From this stage, the horizontal tectonic compression increases and the majority of the fluid migrated under high pressure, characterised by brecciated and crack-seal vein. The tectonic burial increased due to the overthrusting, that is pointed out by the increase of the precipitation temperature of the cements. Afterwards, up- or downward migration of SO₄²⁻, Ba²⁺ and Mg²⁺-rich fluids, which migrated probably along the décollement level, allows a precipitation in thermal disequilibrium. This period corresponds to the onset of the thrusting in the Ionian Zone. The last stage characterised the uplift of the Berati belt, developing a selective karstification due likely to the circulation of meteoric fluid.The main results of the fluid flow modelling show that the Upper Cretaceous–Paleocene carbonate reservoirs in the Ionian zone have been charged from the Tortonian onward, and that meteoric fluid migration should have intensely biodegraded the hydrocarbon in place. Concerning the migration paths, it has been demonstrated that the thrusts act principally as flow barriers in Albania, mainly due the occurrence of evaporites (non-permeable), except in the foreland, where they do not occur.     

Gendering transnational communities: a comparison of Singaporean and British migrants in China

Studies of transnational communities and transnational labour migration have focused almost exclusively on the movement of low-skilled and unskilled workers across international boundaries. While these groups may be numerically dominant, it must be recognised that there are increasing numbers of managers and professionals engaged in work-related migration in association with the intensification of economic globalisation processes. Work which has been conducted on highly skilled migrants has largely been limited to examinations of intra-firm mobility and the workspace. This approach fails to consider the ways in which the migrants' experiences are embedded in the social, economic and political practices of the host country, but also in a specific household context. It is unsurprising, therefore, that the gendered dimensions of the life of these migrants and their accompanying family members has been somewhat under-researched.Flows of expatriates can lead to the constitution of both ‘communities of transnationals', as particular cities become foci of the activities of the ‘transnational capitalist class', as well as ‘transnational communities' which involve regular and sustained contact between individuals across national boundaries. In this paper we examine these social formations using two groups of migrants––British and Singaporean migrants to China (both mainland China and the Hong Kong SAR). We focus on the gender characteristics of these groupings, but also the gender division of labour in the creation and maintenance of these ‘communities'. The paper is based on qualitative research carried out in China, Singapore and the UK 1997–2001.     

Migration and accumulation characteristics of natural gas hydrates in the uplifts and their slope zones in the Qiongdongnan Basin,China

Various factors controlling the accumulation of natural gas hydrates (NGHs) form various enrichment and accumulation modes through organic combination. This study mainly analyzes the geological and geophysical characteristics of the NGHs occurrence in the uplifts and their slope zones within the deep-water area in the Qiongdongnan (QDN) Basin (also referred to as the study area). Furthermore, it investigates the dominant governing factors and models of NGHs migration and accumulation in the study area. The results are as follows. (1) The uplifts and their slope zones in the study area lie in the dominant pressure-relief direction of fluids in central hydrocarbon-rich sags in the area, which provide sufficient gas sources for the NGHs accumulation and enrichment through pathways such as gas chimneys and faults. (2) The top and flanks of gas chimneys below the bottom simulating reflectors (BSRs) show high-amplitude seismic reflections and pronounced transverse charging of free gas, indicating the occurrence of a large amount of gas accumulation at the heights of the uplifts. (3) Chimneys, faults, and high-porosity and high-permeability strata, which connect the gas hydrate temperature-pressure stability zones (GHSZs) with thermogenic gas and biogenic gas, form the main hydrate migration system. (4) The reservoir system in the study area comprises sedimentary interlayers consisting of mass transport deposits (MTDs) and turbidites. In addition, the reservoir system has developed fissure- and pore-filling types of hydrates in the pathways. The above well-matched controlling factors of hydrate accumulation enable the uplifts and their slope zones in the study area to become the favorable targets of NGHs exploration.©2022 China Geology Editorial Office.     

迁移八律与中国人口迁移

中国人口迁移具有下列八个特征：１，提高生活质量是经济目的迁移的主要原因，非经济目的迁移违反经济规律时不能巩固；２，在城市化过程中，乡村迁往城市是主要迁移方向；３，整体男性迁移多，轻工劳务和婚姻迁移突出地区女性迁移多；４，独身青年迁移多；５，短距离迁移多，高素质人口迁移距离较长；６，迁移有圈层递补现象；７，强迁移方向必然带来较弱的迁移回流，当两地经济势能接近和递转时，回流加强；８，城市化过程中大城市迁入人口比重大，吸引迁移的范围广。可见，列文斯坦提出的人口迁移规律基本上适合中国的实际，中国人口迁移的实际又丰富了列文斯坦的人口迁移规律。     

叠前地震数据的平面波深度偏移法

提出了一套基于平面波分解的波动方程叠前地震数据深度偏移方法. 通过对共炮点道集和共偏移距道集地震数据的平面波分解,分别得到适用于单平方根波场外推方程和双平方根波场外推方程的共ps（炮点坐标平面波参数）平面波道集和共ph（偏移距坐标平面波参数）平面波道集. 在对共炮点道集和共偏移距道集地震数据的平面波分解时,不需要进行通常意义下的τ p变换计算. 通过对共ps平面波道集和共ph平面波道集的偏移效果对比,我们认为在速度弱横向变化介质中,两种平面波道集偏移方法的效果相当,但对于速度强横向变化介质,共ps平面波道集偏移方法的效果要优于共ph平面波道集偏移方法. 在计算效率方面,共ps平面波道集偏移方法与共ph平面波道集偏移方法基本相同.     

Emotional labour/body work: The caring labours of migrants in the UK’s National Health Service

The provision of care is an increasingly pressing issue in the Global North. With an ageing population and policies encouraging women into the labour market, there is a growing need for workers to undertake paid caring. This poses important and urgent questions about the social organisation of labour markets. Care work typically is low paid and undertaken in precarious, informal, or temporary situations. Many posts are filled by economic migrants, raising concerns about a care deficit in sending countries. In this paper we examine the ‘caring work’ undertaken by migrant workers in a West London Hospital. We employ a twofold characterisation of caring work. Like other bottom-end service sector work, this work is characterised by the face-to-face ‘emotional labour’. However, it also requires ‘body work’: close and often intimate physical contact between carers and those they care for. We argue that both of these aspects are important in understanding how caring work is constructed as poorly regarded and low paid. We show how these features play out in particular ways for migrant workers employed in such caring work.