Standard cumulative semivariograms of stationary stochastic processes and regional correlation

The standard cumulative semivariograms (SCS), obtained analytically from the currently employed stationary stochastic processes, provide a basis for the model identification and its parameter as well as regional correlation estimations. The analytical solutions for different stationary stochastic processes such as independent (IP), moving average (MA), autoregressive (AR), and autoregressive integrated moving average ARIMA (1,0,1) processes give rise to different types of SCSs which can be expressed in terms of the autocorrelation structure parameters only. The SCSs of independent and MA processes appear as linear trends whereas other type of processes have SCSs which are nonlinear for short distances but become linear at large distances. Irrespective of the stationary stochastic process type the linear portions of SCSs have unit slopes. The vertical distance between these linear portions and that of the IP cumulative semivariogram (CS), provide an indicator for measuring the regional correlation. In the case of stationary processes, the straight line portions of any CS are parallel to each other. Hence, it is possible to identify the model from the sample CS. Finally, necessary procedures are provided for the model parameters estimation. The methodology developed, herein, is applied to some hydrochemical ions in the groundwater of the Wasia aquifer in central part of Kingdom of Saudi Arabia.     

Three‐dimensional seismic analysis of sediment waves and related geomorphological features on a carbonate shelf exposed to large amplitude internal waves,Browse Basin region,Australia

This study analyses the three‐dimensional geometry of sedimentary features recorded on the modern sea floor and in the shallow subsurface of a shelf to upper slope region offshore Australia that is characterized by a pronounced internal wave regime. The data interpreted comprise an extensive, >12 500 km² industrial three‐dimensional seismic‐reflection survey that images the northern part of the Browse Basin, Australian North West Shelf. The most prominent seismic–morphological features on the modern sea floor are submarine terrace escarpments, fault‐scarps and incised channels, as well as restricted areas of seismic distortion interpreted as mass wasting deposits. Besides these kilometre‐scale sea floor irregularities, smaller bedforms were discovered also, including a multitude of sediment waves with a lateral extent of several kilometres and heights up to 10 m. These sedimentological features generally occur in extensive fields in water depths below 250 m mostly at the foot of submerged terraces, along the scarps of modern faults and along the shelf break between the outer shelf and the upper continental rise. Additional bedforms that characterize the more planar regions of the outer shelf are elongate, north‐west/south‐east oriented furrows and ridges. The formation of both sediment waves and furrow‐ridge systems requires flow velocities between 0·3 m sec^?1 and 1·5 m sec^?1, which could be generated by oceanic currents, gravity currents or internal waves. In the studied setting, these velocities can be best explained as being generated by bottom currents induced by internal waves, an interpretation that is discussed against oceanographic background data and modelling results. In addition to the documentation of three‐dimensional seismic–geomorphological features of the modern sea floor, it was also possible to map kilometre‐scale buried sediment wave fields in the seismic volume down to ca 500 ms two‐way‐time below the present sea floor, indicating the general potential for the preservation of such bedforms in the sedimentary record.     

Correlation Fractal and Multifractal Characteristics of Seismic Activity in the Taiwan Area, China

Based on the analysis of newly collected data of plate tectonics, distribution of active faults and crustal deformation, the Taiwan area is divided into two seismic regions and six seismic belts. Then, correlation fractal dimensions of all the regions and belts are calculated, and the fractal characteristics of hypocenteral distribution can be quantitatively analyzed. Finally, multifractal dimensions Dq and f(α) are calculated by using the earthquake catalog of the past 11 years in the Taiwan area. This study indicates that (1) there exists a favorable corresponding relationship between spatial images of seismic activity described with correlation fractal dimension analysis and tectonic settings; (2) the temporal structure of earthquakes is not single but multifractal fractal, and the pattern of Dq variation with time is a good indicator for predicting strong earthquake events.     

准噶尔盆地彩南地区石树沟群地震层序划分与层序地层学解释

从地震资料入手,根据某些古凸起部位石树沟群内部存在的削截、上超、下超等不整合反射,将彩南地区石树沟群划分为3个地震层序。通过区域追踪以及钻井和露头资料的综合分析,发现这3个地震层序分别与头屯河组、齐古组和喀拉扎组3个岩石地层单元相对应。头屯河组顶界的不整合系构造抬升剥蚀所形成,属构造成因,齐古组顶界的不整合系丘形侧积作用所形成,属沉积成因。地震相分析表明这3个层序（组）为3期物源来自北北东向克拉美丽山的洪积扇沉积,其地层发育和沉积相特征受构造、物源和古气候3大因素的控制。在地震资料所揭示出的石树沟群内部和顶界不整合面附近及某些丘形、透镜形沉积体中,存在多种可能的地层圈闭。     

高精度相位相关速度分析技术在海上地震资料中的应用

海上复杂构造区地震资料数据信噪比低,以叠加能量法为主的常规速度分析方法其速度分辨率和精度不能满足精细处理的要求。以南海东部某工区为靶区,对比研究了高精度相位相关速度分析法与常规叠加能量速度分析法,前者提高了速度谱在空间和时间上的精度,得到效果较好的地震叠加剖面,特别是低信噪比区域的成像精度有较大提高。     

薄层地震响应分析及识别技术

对薄层地震响应的振幅,频谱等特征进行了详细的分析,并分析了影响该地震的应波形特征的因素。同时,利用积分能谱技术对其进行处理,可以识别出薄层的厚度变化及透镜体的存在。实际应用表明,该项技术较常规的时频分析方法有更高的分辨能力。     

相关和频谱分析法在岩溶系统中的应用研究综述

岩溶含水层由多重含水介质组成,具有高度的非均质性,从系统角度出发,将岩溶系统看作是一个过滤器,将降雨作为输入信号,泉流量、水位、电导率、浊度等物理化学参数作为输出量进行相关和频谱分析是认识岩溶系统内部结构特征的有效方法。文章综述了相关和频谱分析法在岩溶系统研究中的应用,首先介绍了相关和频谱分析法基本理论的形成、发展过程和研究意义,然后总结了如何根据不同的研究目的选择相关和频谱分析法使用的时间序列的长度、周期和类型,最后阐述了该方法应用于岩溶系统分析的局限性。     

晚第四纪湖泊沉积物盐类与碎屑矿物反相关关系的沉积学解释

湖泊沉积物中矿物组合是古气候环境研究的敏感性指标之一, 充分认识湖泊沉积物中各类矿物组合类型、沉积过程, 对正确解释矿物学指标有重要意义. 我国晚第四纪湖泊沉积记录中, 盐类矿物与碎屑矿物含量普遍存在反相关关系, 影响了矿物组合作为气候指标的解释和应用. 从地球科学的角度正确理解这种关系, 可以为湖泊动力学以及古气候环境定量研究提供重要的科学依据. 选择甘肃民勤盆地石羊河下游终端湖猪野泽不同位置5个全新世剖面, 在明确湖泊沉积物来源、搬运方式和沉积动力机制的基础上, 研究了以碳酸盐矿物为主的盐类矿物含量与粒度指标之间的关系. 结果表明:猪野泽各剖面砂层富含的中砂、细砂沉积物主要是来自于巴丹吉林沙漠和腾格里沙漠的风成砂; 水动力作用主导了湖相沉积层200 μm以下沉积物的沉积, 风力作用对20~70 μm粉砂组分沉积也有所贡献. 同时, 猪野泽湖相沉积层中高含量的碳酸盐主要来自于流水搬运, 湖相沉积层位200 μm以下的粉砂和极细砂是碳酸盐的主要富集区. 综上所述, 干旱区湖泊沉积物中盐类矿物含量与其沉积过程密切相关, 盐类矿物在全球变化研究中的应用要建立在充分研究其沉积动力机制的基础上.     

多尺度随机孔洞介质地震波正演及其逆时成像

常规地震勘探理论无法完全解释复杂多变的地质特征,较难达到高精度地震资料处理的目的,因此必须发展适应复杂非均匀介质的地震波场传播理论,以更好地刻画真实的复杂构造、岩性、裂隙油气藏的特点。根据实际火山岩样的随机特征,构建了相应的多尺度组合型随机孔洞介质模型,并进行了高精度地震波正演数值模拟和逆时成像研究,制作了在不同频率条件下的自激自收剖面和逆时偏移剖面,计算结果表明,构建的多尺度随机孔洞介质模型可以有效模拟真实的地质变化特征,同时指出准确区分由地层随机非均匀性引起的散射波场响应和干扰信号是实现高分辨率地震勘探的前提。     

煤矿采区三维地震探采对比效果的分析与思考

通过介绍兖州、淮南等11个矿区20多个煤矿采区三维地震成果,对各矿探采对比情况进行统计与分析,总结出影响三维地震勘探成果精度的5个技术问题,并指出造成这些问题的3个主要原因,即:野外施工质量普遍下降;方法研究工作严重滞后;三维地震资料二维解释仍很普遍。为提高采区三维地震勘探成果精度提出了6点建议,即:推广高密度三维地震技术,解决精细探查问题;围绕共性关键问题,开展攻关研究与示范应用;发挥产学研结合优势,挖掘现有技术的潜力;加强地震行业自律,施行市场准入制度;集中优势技术力量,加强基础理论研究以及开展煤矿井下地震技术研发,提高地质保障水平。     

三维地震与测井资料在多煤层对比中的应用研究

陆相成煤环境及断陷构造特点,致使二连盆地内煤层具有层数多、间距小、厚度横向变化大、标志层少等特点,利用钻探资料进行煤层对比难度大,其结果将直接影响对煤层、煤质评价及煤炭资源量估算。考虑到研究区煤层赋存特点,利用三维地震成果,对该区进行了煤层辅助对比,其结果与原有7个钻孔煤层对比成果存在差异。通过三维地震层位对比与构造解释方案的核查,结合波阻抗反演结果和测井资料重新解释,认为三维地震的煤层对比是合理的。该实例表明,综合利用测井资料、三维地震解释和波阻抗反演等,可有效提高煤层对比的可靠性,提高煤炭资源地质勘探阶段的控制精度。     

高分辨率三维地震资料处理技术及应用

高分辨率地震勘探技术贯穿于野外采集、室内资料处理和解释各个环节。文章从三维地震资料处理角度出发,探讨高分辨率、高信噪比和高保真度处理的关键技术措施,即波场净化处理,振幅、频率和相位补偿,叠前反褶积,静校正和动校正及叠后频谱整形。最后以实际资料说明经高分辨率处理后,频宽达到350Hz,给解释人员提供优质剖面,为分辨小间距薄煤层奠定基础。     

复杂海底各种地震波的射线追踪与运动学特征

为了实现适应崎岖海底、大陡坡、海底火山等复杂海底地质条件且灵活、稳定、精度高的射线追踪方法,并基于该方法详细分析复杂海底条件下各种地震波型的运动学特征,综合多种算法的优势,实现了一种快速推进迎风插值射线追踪方法。首先,采用混合网格法剖分复杂海底地质模型;其次,通过融入迎风差分思想的线性插值策略来构建精度高、无条件稳定且灵活的局部走时和射线路径计算公式;然后,综合应用这些公式和多级次快速推进法,灵活计算整个模型各种类型地震波的走时,并基于逆向追踪方法计算射线路径;最后,对该方法进行了精度分析,发现其能够获得相对高的走时和射线路径计算精度,且反射波的计算精度远高于入射波。此外,计算实例分析显示,初至波中富含折射波和陡倾构造的反射波在很大偏移距还能被接收,崎岖海底各种波型传播路径复杂;基于此提出加大采集排列长度和采用直达波走时可提高复杂构造成像质量等复杂海底地震数据采集与处理方面的思考与建议。     

三维地震探采对比及再分析初探

寺河矿为一个千万吨级特大型现代化矿井,截止2006年底,矿井三维地震勘探面积已达51km^2,目前采掘范围为二盘区和三盘区,面积分别为6．8km^2和2．8km^2。对比三维地震解释成果与矿井采掘区域实际揭露地质异常,发现早期的常规解释技术手段,在山区复杂地震地质条件下,勘探效果较差,难以满足高产高效矿井生产要求。建议根据采掘得到的相关煤层底板标高、补充钻孔数据、构造及异常数据,利用最新解释技术,在原有地震资料解释技术的基础上,重新进行层位标定,重点利用地震方差体解释技术及属性分析,更好地解释断层、陷落柱等地质异常,进而提高解释精度。     

冷泉羽状流地震波场频谱特征与气含量关系研究

为深入研究羽状流地震响应特征以及羽状流气含量反演,利用实际羽状流地震偏移剖面中单道和多道地震数据,首先进行地震波时域波形特征分析以及地震波场频谱特征分析,羽状流时域波形呈现出散射波动特征,其频谱较宽,表现出开叉较多的散射波频谱特征.然后通过已有气含量与振幅属性关系模型反演气含量,提取羽状流地震频谱参量.最后进行羽状流地...     

Recent morphology and sedimentary processes along the western slope of Great Bahama Bank (Bahamas)

Carbonate slopes and associated resedimented deposits have recently gained renewed interest because they represent volumetrically significant parts of carbonate platforms. Carbonate slopes are highly variable compositionally, architecturally and spatially due to a spectrum of sediment sources, resedimentation processes and controlling factors. Here, new high resolution acoustic data (including EM 302 multi‐beam echo‐sounder and very high resolution seismic) and piston cores document highly diverse and complex morphological features along the north‐western slope of Great Bahama Bank. The recent morphology of the slope is the result of the interplay between depositional and erosive processes that vary through time and along strike. The different sedimentary processes are recorded as a Pleistocene lowstand surface, characterized by many erosional features and a Holocene sedimentary wedge along the upper to middle slope that partially covers the underlying Pleistocene surface. Sedimentary processes during the Holocene are dominated by density cascading flows, which export muddy aragonitic sediment from the platform top towards the slope. Sedimentation rates, however, vary along strike due to platform top morphology combined with the variable strength of the basinal current. Reefs and islands in the Bimini area block off‐bank sediment export, and shoals and tidal deltas from Cat Cay to the south reduce the density cascading processes. Numerous small and large slope failure scars show the instability of the steep slopes of Great Bahama Bank. Bottom currents dominate the lower slope and the basin. Striations and moats are the morphological expressions of current directions, while areas of non‐deposition document strong current and concomitant removal of off‐bank transported sediment along parts of the slope, while the Santaren Drift and the drift on the north‐western edge of Great Bahama Bank act as the depositional locus for the fine‐grained sediments transported in the current.     

Geologic structure and correlation of the Berriasian-Lower Aptian productive beds of the Gydan Peninsula (Russian Arctic)

We discuss the geologic structure of the Berriasian-Lower Aptian deposits of the Gydan Peninsula. Eight seismic sequences have been distinguished; most of them are associated with Lower Cretaceous regional clinoforms of West Siberia, their characteristics are given. A correlation of productive beds was based on the stratotype sections of the Yamal and Gydan Peninsulas as well as seismic and well data. A sequence stratigraphic model of the Berriasian-Lower Aptian complex is proposed.     

青藏高原东缘湖相沉积和黄土高原黄土沉积磁化率与粒度相关性对比*

为探讨构造稳定地区(如黄土高原)和构造活跃地区(如青藏高原东缘)粉尘沉积物中磁化率(SUS)与粒度的相关性及其对环境事件的指示意义,本次研究分析了黄土高原蓝田剖面黄土—古土壤样品和青藏高原东缘湖相沉积样品的粒度和磁化率记录。黄土高原黄土—古土壤沉积SUS与2~10 μm粒度组分最强正相关,青藏高原东缘湖相沉积的SUS与2~10 μm粒度组分最强负相关,反映2~10 μm粒度组分为黄土高原和青藏高原乃至亚洲干旱—半干旱地区连续稳定敏感的背景沉积组分。黄土高原黄土—古土壤沉积的SUS与32~63 μm粒度组分最强负相关,青藏高原东缘湖相沉积的SUS与32~63 μm粒度组分最强正相关,反映32~63 μm粒度组分不仅是黄土高原尘暴事件沉积的敏感指标,也是青藏高原东缘湖相沉积记录的地震事件敏感指标。SUS与粒度组分的相关性在青藏高原东缘地区地震事件层开始部分高于结束部分,也较好地反映地震事件为研究区添加新鲜沉积物后随地形地貌恢复逐步减少的过程。SUS与粒度组分相关性也受当地物源的影响。     

青藏高原东缘湖相沉积和黄土高原黄土沉积磁化率与粒度相关性对比*

为探讨构造稳定地区(如黄土高原)和构造活跃地区(如青藏高原东缘)粉尘沉积物中磁化率(SUS)与粒度的相关性及其对环境事件的指示意义,本次研究分析了黄土高原蓝田剖面黄土—古土壤样品和青藏高原东缘湖相沉积样品的粒度和磁化率记录。黄土高原黄土—古土壤沉积SUS与2~10 μm粒度组分最强正相关,青藏高原东缘湖相沉积的SUS与2~10 μm粒度组分最强负相关,反映2~10 μm粒度组分为黄土高原和青藏高原乃至亚洲干旱—半干旱地区连续稳定敏感的背景沉积组分。黄土高原黄土—古土壤沉积的SUS与32~63 μm粒度组分最强负相关,青藏高原东缘湖相沉积的SUS与32~63 μm粒度组分最强正相关,反映32~63 μm粒度组分不仅是黄土高原尘暴事件沉积的敏感指标,也是青藏高原东缘湖相沉积记录的地震事件敏感指标。SUS与粒度组分的相关性在青藏高原东缘地区地震事件层开始部分高于结束部分,也较好地反映地震事件为研究区添加新鲜沉积物后随地形地貌恢复逐步减少的过程。SUS与粒度组分相关性也受当地物源的影响。