秦岭南缘青川断裂新生代变形特征及其走滑运动学转换

青川断裂作为秦岭构造带南部边界断层,新生代以来受到印度-欧亚大陆碰撞产生的远场效应,发生了强烈的走滑复活,调节了青藏高原隆升和向东扩展。本文基于错断地貌测量与断裂带脆性变形的野外调查,建立了该断裂新生代2期走滑运动历史,并讨论了走滑运动学转换的大地构造意义。沿断裂带河流水系偏移地貌分析发现,主要河流的Ⅳ级支流沿断裂发生一致的右旋偏移,指示断裂右旋位错量在200~800 m;河流阶地的右旋位错量在49~62 m。野外调查发现,青川断裂发育5~100 m宽的断裂破裂带,主要由断层泥、磨砾岩、断层透镜体等组成,S-C组构发育,磨砾石旋转定向排列。断裂破碎带运动学指向记录了青川断裂2期脆性走滑变形:早期为左旋走滑活动、晚期为右旋走滑活动。结合断裂带东端汉中盆地地层时代和秦岭山地隆升时代,我们推断晚期右旋走滑运动主要发生在上新世以来,调节了碧口地块的向东挤出;而早期左旋走滑运动则很可能是对古近纪晚期青藏高原隆升和扩展的响应。     

郯庐断裂新生代构造演化及其对烃源岩生排烃的影响:以辽东湾坳陷辽中凹陷为例

郯庐断裂带是渤海海域重要的活动断裂带,控制着该地区油气成藏的生储盖运圈保条件。以辽东湾坳陷辽中凹陷为研究对象,利用三维地震资料、平衡剖面分析对郯庐断裂几何学特征、演化特征进行研究;在此基础上,分析郯庐断裂走滑活动对烃源岩发育、分布、演化及生排烃的影响。辽东湾坳陷新生代构造演化分为为五个构造演化阶段、三个构造演化旋回。郯庐断裂走滑活动可错开先期、同期发育的烃源岩,改变烃源岩位置及生烃潜力的空间分布,有利于形成局部水体更深的还原环境,发育生烃潜力更大的烃源岩。走滑活动使断裂带附近地温梯度和大地热流升高,有利于降低生烃门限。郯庐断裂不同时期不同部位具有不同的活动性质,对油气运移起封闭或者运移通道作用。东营组沉积期晚期和明化镇组下段沉积期至今的断裂走滑活动与烃源岩大量生排烃期、油气成藏时期具有良好的匹配关系,提出郯庐断裂走滑活动可形成"拖曳"生排烃现象,使与走滑断层相关的圈闭中即使烃源岩条件较差亦可能具有勘探价值,从而突破了传统的油气勘探思路。     

歧口凹陷北大港潜山南北向走滑断裂的河道化作用分析

通过北大港地区重力异常资料、三维地震资料分析,证实在北大港潜山上发育具有左旋走滑性质的红7-1断裂,其夹持于大张坨断裂与港西断裂之间,呈弧形沿南北方向展布。该断裂在古近系早中期均有活动,对多个层位砂体分布具有明显的控制作用,在该走滑断裂弧形带南侧,砂体厚度突变增大,呈"点源式"分布,从而形成明显的、且具有继承性的"沟-扇"对应关系。结合重矿物分析及北大港潜山上下切河道追踪发现,在走滑断裂顶部发育一系列下切河道;这些河道下切深度可达230～280ms,它们可以沟通板桥次凹与北大港潜山南翼,在过补偿阶段将板桥次凹的沉积物沿下切河道搬运到北大港潜山南侧的歧北次凹。可见,北大港潜山上近南北向的走滑断裂可以形成下切河道并起到搬运沉积物的作用(即断裂的河道化作用),进而在过补偿阶段控制板桥次凹与北大港潜山南翼的物源分配形式,所以,板桥次凹和歧北次凹在一定程度上均隶属于沧县隆起物源体系。     

地震破裂带特殊部位大型滑坡及其基于构造地貌发生模型的机制解释:以东河口抛射型滑坡为例

汶川地震在龙门山地区激发了大量的次生地质灾害,其中尤以滑坡灾害分布最为广泛和严重。在所有滑坡灾害中,东河口滑坡发生在北川破裂带的北东端点,具有相当的特殊性,并造成了大量的生命财产损失。东河口滑坡是一种抛射型滑坡,具有与其他如重力或者降雨作用导致的滑坡不同的特点,即没有统一连续的滑动面,由上部比较深陡和下部比较浅缓的截然分开的两部分组成,在强地震加速度的作用下,滑坡体被抛射并在与地面发生碰撞之前沿抛物线轨迹运行。文章综合分析了东河口抛射型滑坡发生的地质地貌条件,并解释了该抛射型滑坡发生的动力源机制。结果显示,东河口滑坡区的滑坡带和翼状裂隙带在北川破裂带两侧的规则分布受控于断层的运动方式和滑坡的空间分布位置;此外,除地震动水平加速度和地质地貌条件外,垂直加速度和断层的运动方式对地震滑坡的激发也起着重要的作用。     

Evolution of fault geometry and development of strike-slip basins: Comparative studies on the transform zones in Turkey and Japan

Abstract Although the origins of pull-apart basins and push-up bulges have been discussed by numerous geologists, no discussion has been held on the development process of the basins based on recent active traces and Quaternary chronology. The author has investigated recent fault-active traces and fault topography in the Havza-Ladik, Erbaa-Niksar, Susehri-Golova and Erzincan sedimentary basins along the North Anatolian fault in northern Turkey and the Suwa basin along the Itoigawa-Shizuoka tectonic line (fault system) in central Japan. As a result of this investigation, the locations and sense of deformation of recent active traces seldom coincide with topographic scarps along basin margins in the studied basins. The fault traces have migrated from the basin margins to the center of the basins and become straight. Because of this migration, jogs are extinguished and basins stop subsiding as time passes. Fault topography formed by a strike-slip fault has a certain life span, and the life span is in proportion to the size of the topography. Fault topography formed by various sizes of jogs of a strike-slip fault is formed and extinguished in the corresponding time range, and this extinction is repeated in the course of migration of fault traces.     

死海（约旦）里散半岛的重磁勘查

里散半岛位于非洲板块和阿拉伯板块支接处的死海盆地中。该盆地面积大，构造简单且有下沉运动，说明它是一位张型盆地。由重力异常数据发现死海盆地可划分成沿南北延伸各约３０ｋｍ长的几个块体，里散半岛是其一最深的一个。一生代沉积厚度约６ｋｍ，更新世沉积厚度为９ｋｍ。死海盆地的拉张距离为２０ｋｍ，表明死海盆地的年龄约３．３Ｍａ。里散半岛下部的前寒武纪结晶基底磁化率较高，这与区内延续的构造活动性有关。     

High inside corners at ridge-transform intersections

A large topographic high commonly occurs near the intersection of a rifted spreading center and a transform fault. The high occurs at the inside of the 90° bend in the plate boundary, and is called the high inside corner, while the area across the spreading center, the outside corner, is often anomalously low. To better understand the origin of this topographic asymmetry, we examine topographic maps of 53 ridge-transform intersections. We conclude the following: (1) High inside corners occur at 41 out of 42 ridge-transform intersections at slow spreading ridges, and thus should be considered characteristic and persistent features of rifted slow spreading ridges. They are conspicuously absent at fast spreading ridges or at spreading centers that lack a rift valley. (2) High inside corners occur wherever an axial rift valley is present, and an approximate 1:1 correlation exists between the relief of the rift valley and the magnitude of the asymmetry. (3) Large high inside corners occur at both long and short transform offsets. (4) High inside corners at long offsets decay off-axis faster than predicted by the square root of age cooling model, precluding a thermalisostatic origin, but consistent with dynamic or flexural uplift models.These observations support the existing hypothesis that the asymmetry is due to the contrast in lithospheric coupling that occurs in the active transform versus the inactive fracture zone. Active faulting in the transform breaks the lithosphere along a high angle fault, permitting vertical movement of the inside corner block, whereas the inactive fracture zone forms a weld that couples the outside corner to the adjacent block, preventing it from rising. Large asymmetry at very short transform offsets appears to be caused by the added effect of a second uplift mechanism. Young lithosphere in the rift valley couples to the older plate, and when it leaves the rift valley it lifts the older plate with it. At very short offsets, this coupled uplift acts upon the high inside corner; at long offsets, it may upwarp the older plate or its expression may be muted.     

From oblique subduction to intra-continental transpression: Structures of the southern Kermadec-Hikurangi margin from multibeam bathymetry,side-scan sonar and seismic reflection

The southern Kermadec-Hikurangi convergent margin, east of New Zealand, accommodates the oblique subduction of the oceanic Hikurangi Plateau at rates of 4–5 cm/yr. Swath bathymetry and sidescan data, together with seismic reflection and geopotential data obtained during the GEODYNZ-SUD cruise, showed major changes in tectonic style along the margin. The changes reflect the size and abundance of seamounts on the subducting plateau, the presence and thickness of trench-fill turbidites, and the change to increasing obliquity and intracontinental transpression towards the south. In this paper, we provide evidence that faulting with a significant strike-slip component is widespread along the entire 1000 km margin. Subduction of the northeastern scrap of the Hikurangi Plateau is marked by an offset in the Kermadec Trench and adjacent margin, and by a major NW-trending tear fault in the scarp. To the south, the southern Kermadec Trench is devoid of turbidite fill and the adjacent margin is characterized by an up to 1200 m high scarp that locally separates apparent clockwise rotated blocks on the upper slope from strike-slip faults and mass wasting on the lower slope. The northern Hikurangi Trough has at least 1 km of trench-fill but its adjacent margin is characterized by tectonic erosion. The toe of the margin is indented by 10–25 km for more than 200 km, and this is inferred to be the result of repeated impacts of the large seamounts that are abundant on the northern Hikurangi Plateau. The two most recent impacts have left major indentations in the margin. The central Hikurangi margin is characterized by development of a wide accretionary wedge on the lower slope, and by transpression of presubduction passive margin sediments on the upper slope. Shortening across the wedge together with a component of strike-slip motion on the upper slope supports an interpretation of some strain partitioning. The southern Hikurangi margin is a narrow, mainly compressive belt along a very oblique, apparently locked subduction zone.     

对伸展域变换构造研究的两点思考

在变换构造研究现状的基础上，从概念和分类两方面提出了研究中存在的两个问题：传递带和调节带的分类不清以及变换构造带的识别问题，并对这两个问题做出了探讨。针对传递带和调节带的分类不明确、两者具体范围和边界混淆的问题，对传递带和调节带的关系作了研究；对变换构造带的识别问题，从应力机制、运动学特征和几何形态三方面论述了变换构造带和走滑断裂带的异同：     

Slip sense inversion on active strike-slip faults in southwest Japan and its implications for Cenozoic tectonic evolution

Analyses of deflected river channels, offset of basement rocks, and fault rock structures reveal that slip sense inversion occurred on major active strike-slip faults in southwest Japan such as the Yamasaki and Mitoke fault zones and the Median Tectonic Line (MTL). Along the Yamasaki and Mitoke fault zones, small-size rivers cutting shallowly mountain slopes and Quaternary terraces have been deflected sinistrally, whereas large-size rivers which deeply incised into the Mio-Pliocene elevated peneplains show no systematically sinistral offset or complicated hairpin-shaped deflection. When the sinistral offsets accumulated on the small-size rivers are restored, the large-size rivers show residual dextral deflections. This dextral offset sense is consistent with that recorded in the pre-Cenozoic basement rocks. S–C fabrics of fault gouge and breccia zone developed in the active fault zones show sinistral shear sense compatible with earthquake focal mechanisms, whereas those of the foliated cataclasite indicate a dextral shear sense. These observations show that the sinistral strike-slip shear fabrics were overprinted on dextral ones which formed during a previous deformation phase. Similar topographic and geologic features are observed along the MTL in the central-eastern part of the Kii Peninsula. Based on these geomorphological and geological data, we infer that the slip sense inversion occurred in the period between the late Tertiary and mid-Quaternary period. This strike-slip inversion might result from the plate rearrangement consequent to the mid-Miocene Japan Sea opening event. This multidisciplinary study gives insight into how active strike-slip fault might evolves with time.