Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin,Malawi Rift (EARS)

The Cenozoic East African Rift System (EARS) is an exceptional example of active continental extension, providing opportunities for furthering our understanding of hydrocarbon plays within rifts. It is divided into structurally distinct western and eastern branches. The western branch comprises deep rift basins separated by transfer zones, commonly localised onto pre-existing structures, offering good regional scale hydrocarbon traps. At a basin-scale, local discrete inherited structures might also play an important role on fault localisation and hydrocarbon distribution. Here, we consider the evolution of the Central basin of the Malawi Rift, in particular the influence of pre-existing structural fabrics.Integrating basin-scale multichannel 2D, and high resolution seismic datasets we constrain the border, Mlowe-Nkhata, fault system (MNF) to the west of the basin and smaller Mbamba fault (MF) to the east and document their evolution. Intra basin structures define a series of horsts, which initiated as convergent transfers, along the basin axis. The horsts are offset along a NE–SW striking transfer fault parallel to and along strike of the onshore Karoo (Permo-Triassic) Ruhuhu graben. Discrete pre-existing structures probably determined its location and, oriented obliquely to the extension orientation it accommodated predominantly strike-slip deformation, with more slowly accrued dip-slip.To the north of this transfer fault, the overall basin architecture is asymmetric, thickening to the west throughout; while to the south, an initially symmetric graben architecture became increasingly asymmetric in sediment distribution as strain localised onto the western MNF. The presence of the axial horst increasingly focussed sediment supply to the west. As the transfer fault increased its displacement, so this axial supply was interrupted, effectively starving the south-east while ponding sediments between the western horst margin and the transfer fault. This asymmetric bathymetry and partitioned sedimentation continues to the present-day, overprinting the early basin symmetry and configuration. Sediments deposited earlier become increasingly dissected and fault juxtapositions changed at a small (10–100 m) scale. The observed influence of basin-scale transfer faults on sediment dispersal and fault compartmentalization due to pre-existing structures oblique to the extension orientation is relevant to analogous exploration settings.     

逆断层地震近场地震动影响场和地表形变模拟

本文设计了一个MW7.0级地震的简单的逆断层有限移动源破裂模型,计算了断层周围64个观测点的加速度、速度和位移时程及峰值,简单讨论了近场地震动峰值、断层附近地表永久位移(或地表形变)的分布特点,并讨论了永久位移和地面运动速度大脉冲的关系。重点研究了断层附近三分量的永久位移(或地表形变)大小、方向和地震动作用特点。     

断层泥中石英碎砾溶蚀形貌的测年研究

考虑到同一条断层的同一个位置所取的断层泥中,不同碎砾的溶蚀形貌并不相同,即使是同一个碎砾,其不同的表面,溶蚀形貌也可能不同,将统计学参数估计的方法引入结果处理中,并把在金川水电站坝区F1断层一次所取得断层泥样品碎砾的各个表面的总体当作一个整体进行处理,得出此断层的活动时间可能为早更新世的结果。与ESR法测得的结果基本一致。     

伽师强震群的深部动力学条件

根据天山造山带及其两侧的塔里木盆地和准噶尔盆地的岩石圈二维速度结构、二维密度结构、二维电性结构、壳幔过渡带的详细结构以及大地热流和震源深度的分布,再结合对新疆西北部的蛇绿岩带、高压变质带和岩浆岩分布的综合分析,建立了天山造山带的地球动力学“层间插入消减”模型。该模型认为,塔里木板块的中上地壳在库尔勒断裂附近向天山造山带的中下地壳层间插入;而下地壳连同岩石圈地幔向天山造山带的上地幔俯冲消减。在天山的西段（哈萨克斯坦境内）,费尔干纳地块由北向南插入到南天山之下约180km的深处,在其东段（中国境内）,塔里木盆地由南向北插入南天山之下。这两个具有不同方向的下降板片的接触部位为费尔干纳走滑断裂。我国的伽师、喀什、乌恰地震区均落在这两个具有不同俯冲方向板块的结合部位附近,有着特殊的深部构造背景。南、北两大板块的双向挤压必定产生强大的应力,在地震区附近,这种应力的积累与释放具有4个显著的特点：（1）板片的俯冲消减速度约高达每年22mm左右;（2）应力的积累与释放速率加快;（3）应力释放较容易;（4）应力释放较为集中。这4个特点可能是伽师地区在较短的时间内连续发生数次强震的构造因素。     

自组织竞争神经网络在江苏油田有杆抽油系统故障诊断中的应用

有杆抽油系统的故障诊断技术是国内外采油工程技术中的一个重要研究课题。通过示功图的不同形状特征可以反映抽油机的不同工作状态。将自组织竞争神经网络应用于示功图的识别与分类,建立了一个自组织竞争神经网络模型对示功图进行自动聚类,从而实现故障诊断的自动化。应用江苏油田的实测示功图数据进行实验,可以看出自组织竞争神经网络具有良好的分类能力和泛化性能,是实现油田抽油系统故障诊断的有效技术,具有很强的实用价值和广泛的应用前景。     

基于GPS和水准数据的微粒群算法联合反演祁连山北缘断裂三维滑动速率

将微粒群算法与位错理论模型相结合,采用中国地壳运动观测网络提供的青藏高原地区2001~2004年GPS测量数据和2000~2006年水准测量数据,通过常规定权和附有相对权比的方法对祁连山北缘断裂的三维滑动速率进行联合反演,并与蚁群算法反演结果进行对比。结果表明,微粒群算法收敛速度快、稳定性高,结合经典位错理论模型,是一种可以有效求解断层三维滑动速率反演问题的优化算法,在大地测量反演领域极具应用潜力。     

三门峡断陷盆地及邻区深部结构及成因——来自深地震反射与大地电磁测深的证据

近年来,围绕三门峡断陷盆地中的油气、地热资源做了大量的工作,成因机制研究较少,严重制约了矿产资源的勘探开发。本文在前人研究工作基础上,结合野外地质调查并利用高精度深反射地震剖面、大地电磁（MT）、重磁等地球物理探测技术,对三门峡盆地进行综合研究。发现三门峡盆地主要由东、西2个负花状构造构成,西花状构造体大于东花状构造体;盆地东部边缘以观音堂隆起与洛阳凹陷相邻,观音堂隆起发育有壳内透镜状低速体,其东、西两侧均发育有规模较大的隐伏逆断层。研究区内莫霍面为大约5 km厚度滑脱层,在深反射地震剖面上表现为蚯蚓状反射特征,指示滑脱层为西向运动。莫霍面滑脱层上部与下部新发现多条弧形断层。地质与地球物理资料综合研究表明,莫霍面滑脱层的解耦作用是三门峡断陷盆地花状构造形成的主因;在不同时空构造力系作用下,形成研究区新生代全地壳旋转花状构造盆地。     

河套盆地北缘色尔滕山河流地貌参数特征及其成因分析

地貌形态是构造和地表过程相互作用的复杂产物,主要通过构造活动和岩石的抗侵蚀能力等来调节。构造活动相对较弱的古老造山带往往可以忽略构造驱动的岩石抬升,使得研究岩石抗侵蚀能力对其地貌雕刻的贡献成为可能。但是目前大多数活动造山带地貌研究的结果显示地貌主要受控于活动构造,关于岩性对地貌演化影响的报道较少。色尔滕山山前断裂为河套盆地北缘的一条重要控盆断裂,全新世以来该断裂的活动性较强,曾发生过两次较大震级地震（M6. 4和M5. 9）。前人活动构造研究表明该断裂的活动性具有空间差异,中部乌加河镇活动性最强,两端逐渐减弱。但相对河套盆地北缘其他大型断裂（如狼山山前断裂、乌拉山北缘断裂和大青山山前断裂）,该断裂的地貌参数研究较少。同时其地貌演化特征及发育机理仍然不清楚,这些均制约了对该断裂的变形动力学理解。本文基于30 m分辨率的DEM数据对该断裂进行详细的河流地貌学参数研究,包括使用Arcgis和Matlab脚本提取色尔滕山山前33条河流的子流域盆地面积 高程积分（HI）和相应河道陡峭指数（Ksn）、河道纵剖面及其裂点等地貌学参数。结果表明研究区河流HI值大部分处于0. 40~0. 66之间,其中乌加河镇附近具有高值,流域盆地处于发育的壮年期。瞬态河道和稳态河道均沿着色尔滕山山前断裂走向分布,可能表明色尔滕山山前大部分河道目前处于瞬时地貌向均衡地貌演化阶段,并且通过对比发现瞬态河道裂点成因存在岩性和构造共同控制的现象。河道陡峭指数空间分布差异性较大,乌加河镇附近（S13~S20）陡峭指数较大,向两边陡峭指数逐渐减小,在S8河流以西又有增大的趋势。通过结合岩性和降雨情况分析发现,河道陡峭指数除了受岩性抗侵蚀能力影响外,其分布还与色尔滕山山前断裂垂直滑移速率分布和垂直位错分布基本一致。综合来看,地貌参数的空间分布是岩性差异和色尔滕山山前断裂活动分段差异性共同控制的结果,表明该地区岩性和构造对地貌的协同塑造作用。     

High-resolution record of tectonic and sedimentary processes in growth strata

Growth strata are used to determine the kinematics of synsedimentary structures such as faults. Classical methods of analysis such as thickness versus throw plot consider that the available space created by fault slip in the hanging wall of faults is instantaneously filled up by sediments. This has lead many previous works to identify a cyclic activity for growth faults. Here we perform a careful analysis of the variation of strata thicknesses on each side of a very well documented normal growth fault in the Niger delta. We show that these thickness variations are induced by the alternation of sedimentary processes during continuous fault slip. Suspended-load processes induce either uniform or slightly variable thickness of a large majority of mudstone layers. Bedload processes result in a preferential thickening of sand layers in the hanging wall. These high quality data thus provide strong grounds for doubting the polycyclic growth diagnosed for some faults at the scale of sedimentary cycles and supports the notion that fault displacement rates can be very well behaved. Our study emphasizes the important conclusion that stable fault growth, and related displacement rates, can appear to be punctuated when viewed at the scale of sedimentary cycles. It follows that care should be taken when attempting to derive displacement rates on temporal scales equivalent to those of alternating sedimentological cycles.     

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