Methods and applications of 3-D wave equation common-azimuth prestack migration

To tackle the difficulties of a 3-D full volume prestack migration based on the double-square-root (DSR) one-way wave equation in practical applications, the common-azimuth migration approach is first discussed using dual-domain wave propagators under the theoretical frame of crossline common-offset migration. Through coordinate transforming, a common-azimuth prestack tau migration technology that recursively continues the source and receiver wavefields and picks up the migrated results in the two-way vertical traveltime (tau) direction is developed. The migrations of synthetic data sets of SEG/EAGE salt model prove that our common-azimuth migration approaches are effective in both depth and tau domains. Two real data examples show the advantages of wave-theory based prestack migration methods in accuracy and imaging resolution over the conventional Kirchhoff integral methods. Translated from Oil Geophysical Prospecting, 2006, 41(6): 629–634 [译自: 石油地球物理勘探]     

Chaba (0417) 台风变性前后热力结构特征

运用美国NOAA-15极轨气象卫星高分辨率的AMSU探测资料, 结合NCEP/NCAR再分析资料和GMS-5气象卫星红外云顶亮温(TBB)资料, 对2004年Chaba(0417)台风(TC)变性前后的热力结构特征进行分析。发现变性前TC暖核结构呈对称分布, 在高空存在一强暖心; 变性后原TC对称暖心结构消失, 存在于温带气旋上空的相对暖区呈现出倾斜的非对称分布, 在高、低层各形成一弱的暖区中心, 锋面的斜压特性显著。通过热力结构对比, 进一步揭示出TC在向高纬度方向移动时, 与中纬度系统相互作用发生变性, 实质上是两个相继过程, 即热带气旋的消亡和温带气旋的生成发展。TC西侧高空干冷空气的入侵下沉, 破坏了其发展所需的水汽条件, 造成TC对称暖核结构的削弱和损毁。与此同时, 在TC残留区域, 由于空气较暖且存在气旋式环流, 暖空气在东侧呈气旋式上升, 与西侧高空入侵下沉的干冷空气形成偶极, TC暖气团与冷空气相交发展形成斜压的结果, 则为温带气旋的生成和发展创造了有利条件。     

西湖凹陷中南部油气成藏动力学特征及成藏机理

西湖凹陷以始新世末的玉泉运动和中新世末的龙井运动形成的不整合面为界,将盆地的发展演化分为裂陷、坳陷和区域沉降三个阶段。在盆地演化的不同阶段,不同构造带的沉降速率存在差异,烃源岩的热成熟演化史也不一致。生、排烃史模拟表明：平湖组烃源岩的生烃强度最高,花港组烃源岩的生烃强度相对较小;中央背斜带及其两侧深凹部位烃源岩的生烃强度大于保斜坡带;主要应用Basin Mod盆地模拟软件系统,通过对流体势、温压系统、异常压力的分析,探讨西湖凹陷中南部油气运聚成藏的机理。     

热液体系氩同位素示踪研究

 采用分阶段加热爆裂法测定了不同成因热液矿床脉石英流体包裹体的氩同位素,计算出各温度段内大气氩的相对含量,从而,总结出大气降水热液矿床、再平衡岩浆水热液矿床等成矿流体的氩同位素组成特征及其演化规律。典型的大气降水热液矿床,其成矿流体以具有高大气Ar组分(约95%-100%)为特征;再平衡岩浆水热液矿床成矿流体的Ar同位素组成特征取决于与其有成因关系的初始岩浆水的Ar同位素组成及矿源层和围岩的性质,产于古老变质岩中的,一般以具有低大气Ar组分(约6%-20%)为特征,其它的再平衡岩浆水热液矿床在主成矿温度范围内一般为50%-60%左右。     

兰州第四纪黄土/古土壤序列物源演变: 来自于碳酸盐矿物的证据*

黄土/古土壤的物源研究对于揭示第四纪气候变化和青藏高原隆升历史具有重要意义。本研究以位于黄土高原西部1.4 Ma以来的兰州黄土/古土壤沉积序列为研究对象,基于X射线衍射技术分析了黄土/古土壤中的主要矿物组成,侧重于碳酸盐矿物含量,追溯了兰州黄土/古土壤的直接物源。结果显示: (1)1.4 Ma以来兰州地区黄土/古土壤沉积物的主要直接源区为柴达木盆地沙漠区和阿拉善干旱区。(2)基于二元混合模型计算的潜在原始源区对兰州黄土白云石和总碳酸盐矿物的相对贡献率以及长石与石英比值结果一致支持1.4 Ma以来兰州黄土原始物源发生了多次变化。1.4~1.1 Ma和0.9~0.3 Ma青藏高原东北缘造山带(昆仑山、祁连山)和中亚造山带对兰州黄土的贡献相当,而1.1~0.9 Ma和0.3 Ma以来,中亚造山带对兰州黄土的物源贡献增加,这可能分别是对中更新世气候转型和0.3 Ma以来青藏高原及邻近地区干冷气候增强的响应。1.15 Ma和0.8 Ma兰州黄土/古土壤中高的白云石含量、碳酸盐矿物总含量以及0.8 Ma长石与石英比值的快速升高可能是对“昆黄运动”的响应,进而造成了昆仑山、祁连山对黄土高原物源贡献的增加。     

The Late Silurian Age of the Reference Aralaul Granosyenites–Granite Massif (Northern Kazakhstan)

This work presents the results of U–Pb geochronological studies of alkaline granites of the Aralaul complex of Northern Kazakhstan, which allow one to substantiate their Late Silurian (420 ± 4 Ma) age. Taking into consideration the previously obtained data, we propose a new development scheme of Paleozoic granitoid magmatism in Northern Kazakhstan, which includes Late Ordovician granite–granodiorite (Zerenda and Krykkuduk), Early Silurian granite–leucogranite (Borovoe and Karabulak), Late Silurian granosyenites–granite (Aralaul), and Early Devonian (Balkashino and Orlinogorsk) complexes.     

黄土高原表土磁化率与气候要素的定量关系研究

黄土高原地区已建立多个表土低频磁化率-气候转换函数,为黄土古气候定量重建提供了关键方法。但是表土磁化率变化的气候控制因素的系统研究尚未开展; 同时,低频磁化率部分受到沉积作用的影响,需要寻找气候意义更明确的指标。我们系统采集了黄土高原及周边地区的表土样品,运用相关、回归和因子分析等方法,研究了不同气候要素及其季节变化对表土磁化率和频率磁化率的控制作用。结果显示,湿度是控制黄土高原表土磁化率的主要因素,温度的影响相对较小; 降水的季节分配也有影响,月降水变率较小的地区磁化率较高。在此基础上,选择反映成壤磁性颗粒组分的频率磁化率,建立了频率磁化率-年均降水量的转换函数,为黄土古气候定量估算提供了新的途径。     

中缅油气管道跨断裂地震变形的GNSS观测

中缅油气管道工程是我国重要的能源战略项目,该工程沿线地质背景复杂、破坏性地震多发,尤其是在云南境内跨越的3条大断裂曾发生过7级以上大震,有再次发生破坏性地震的可能性,对管道安全有潜在威胁。中缅油气管道地震观测项目通过在管道与3条断裂交汇处布设3组GNSS观测点,观测地震可能引起的断层位错,进而估计管道可能的变形影响。基于观测数据,分析影响观测的因素及断层位错的观测误差。管道变形承受能力对比结果表明,GNSS跨断裂变形观测系统能够有效观测断裂的位错,进而估计其对管道产生的影响。     

环境干扰事件引起的“形变异常变化”

通过对山东泰安台形变观测受抽水、灌溉影响及烟台台形变观测受载荷影响的分析,认为同一台站的多套形变固体潮仪器"同步异常"的出现应成为判定异常发生的重要准则;对同一应变过程不同形变仪器的响应量级会有所不同,分量式应变仪对异常反映最有效,其次是伸缩仪。对几次"干扰异常"所揭示的问题进行了初步讨论,并在形变异常判定科学思路方面提出了一些建议。     

Reviews on Potash Deposit Metallogenic Conditions

Potash salt is one of key scarce strategic resources. Searching for large scale of potash salt deposit is one big problerm which Chinese academic community faces. Many new discoveries of world potash deposit have been made in recent ten years, which provide abundant practical information and complement the potash metallogenic theory. Through the summary of the potash forming characteristics at home and abroad, the paper studies the potash forming time, tectonic condition, paleogeographic condition, paleoclimate, basin location and salt source. Potash is mainly formed in Permian, Cretaceous, late Jurassic, Cambrian and Devonian. The combination of structure and environment helps to form large scale of evaporation. The climate cycle is related with crust activity. As the other ore deposit, the formation of potash ore also needs dry climate. Potash is the product of final stage in brine evolution, and therefore, it needs persistent drought climate. However, the climate condition is very complicated. Drought climate belt also occurs in humid climate stage, which is controlled by geomorphology. Potash ore can also form in local drought condition. Generally, potash forms in rock salt basin. However, the actual situation is very complicated. Some potash basin is coincided with rock salt basin, some is on one side of rock salt basin; and some are even in the outside of rock salt basin. Salt materials can be from three sources: marine source, terrigenous source and deep source.The paper gives an overview of the research status about the potash deposit forming conditions, which has great guiding significance for searching potash deposit in China. The paper also summarizes the three types of metallogenic models for potash deposit, including epicontinental metallogenic model, abnormal marine evaporation model and rift valley model. The three models are mainly different in material sources, in which the potash in epicontinental metallogenic model is from seawater; the potash in abnormal evaporation model is from nonmarine brine and the potash in rift valley model is mainly from deep material of volcanic activity.