南海西部断裂系研究及其物理模拟实验证据

南海西部断裂系是由四条典型的走滑断裂所组成的断裂系统,是南海扩张的西部边界.此断裂系主要是在白垩纪以来的印-藏碰撞、新生代印支挤出和南海扩张的共同作用下形成的.通过模拟实验,探讨此断裂系的成因、演化过程,认识到此断裂系经历了五期构造运动.     

浅层地震在复杂断裂带探测中的应用研究

拟建中的潍河特大桥地处沂沭大断裂边缘。区内断裂发育,构造复杂,直接会影响大桥基础的稳定性,因而查清区内断裂带的准确位置与分布是大桥工程的关键。探测应用浅层地震折射波方法和选用追逐与相遇观测系统和大小排列相结合的工作方法,准确地查明了区内断裂的准确位置和特征,与钻井资料对比,十分吻合。     

基于构造—地层学的隐蔽圈闭预测——以松南十屋断陷深层为例

综合运用高精度层序地层学、构造一地层学方法,认为十屋断陷深层发育的各类隐蔽圈闭是下一步勘探工作的重要目标。同时,由于构造对沉积的控制作用,在断陷内部不同的构造部位具有不同的隐蔽圈闭分布特征。十屋断陷西部皮家地区、北部张家屯一八屋地区位于油气主要运移指向区,分别由断裂坡折带和以挠曲型褶皱为特征的弯折带控制的储集砂体十分发育,盖层及保存条件也十分优越,是深部原生岩性、地层油气藏最有利的勘探目标区带。     

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.     

Estimation of standing stock of chlorophylla and primary production from remote-sensed ocean color in the Oyashio region, the Western subarctic Pacific, during the spring bloom in 1997

In order to examine the applicability of remotely-sensed ocean color for the estimation of phytoplankton biomass and primary production in the Oyashio region, the western subarctic Pacific, vertical distributions of chlorophylla concentration and primary production were observed in April and May 1997. Spring bloom was observed in both April and May, and the surface concentration of chlorophylla exceeded 40 mg m⁻³. The relationship between the standing stocks of chlorophylla within the layer from the sea surface to one optical depth (0–1/k layer) and the surface chlorophylla concentration is expressed as a Michaelis-Menten equation. The mean ratio of the standing stock of chlorophylla in the euphotic layer to that in the 0–1/k layer was 4.41, this ratio did not significantly differ from 4.61 which was obtained at homogeneous distribution of chlorophylla within the euphotic layer. These facts suggest that the distribution of chlorophylla could be assumed to be homogeneous in the euphotic layer during the spring bloom. Results of primary production measurements by simulatedin situ method were compared with those by an algorithm with two variables; chlorphylla and non-spectral PAR. Daily primary production in the euphotic layer estimated by the algorithm varied in a range of 38–274% of that estimated by incubation, although the primary productions by the algorithm agreed with those by the incubation at a half of stations. Primary production within the euphotic layer calculated using simply the surface data was the same as that estimated using vertical distribution of chlorophylla. These results show that the primary production in the euphotic layer may be estimated from the remote sensed measurements during the spring bloom in the Oyashio region.     

梨树断陷断陷期小宽断裂带构造应力场数值模拟

在小宽断裂带构造解析基础之上,根据地质资料以及前人提供的岩石物理学参数建立了梨树断陷区的二维地质和数值模型。进行了构造应力场数值模拟,分析了梨树断陷小宽断裂带断陷期小宽断裂带断陷期在沙河子期(K1sh)、营城期(K1yc)、登楼库期(K1d)的构造应力场特征。模拟结果显示：(1)沙河子期在左旋走滑应力状态下,小宽断裂带处于近NE—SW方向的拉张应力状态,剪应力在沿着断裂带SW—NE走向逐渐减小; (2)营城期在右旋走滑的应力状态下,小宽断裂带处于近NW—SE向的拉张力状态,剪应力最大值位于断裂带的最中间部位;(3)登楼库期在左旋走滑的应力状态下,断裂带处于SWW—NEE向的张拉应力状态,剪应力最大值位于断裂带西南段。     

东海盆地西湖凹陷平北区断陷层断裂特征及其对圈闭的控制

以基底古隆精细刻画为基础,分析东海陆架盆地西湖凹陷平北区断陷层系断裂发育特征,并探讨断裂对圈闭发育的控制作用,以指导区内构造圈闭搜索与评价。根据古隆起和骨干断裂展布特征,将平北区划分为北部同向多阶断阶区、中部反向多阶断阶区和南部同向单断断阶区等3个次级区带。综合区域应力背景和火山活动期次,厘定出平北区断陷期早、晚两期断裂系统。早期断裂以NE走向为主,控制古隆起发育。晚期断裂数量多、分布广,以NNE走向为主。在南强北弱的区域伸展背景下,断陷晚期断裂发育受早期断裂及古隆起影响,局部应力场发生扭动调整,在平湖组沉积时期表现为南部强伸展、中部张扭和北部弱伸展夹扭动3种不同应力场。在此基础上,明确了张扭性断裂组合及古隆起边缘受断层影响的牵引背斜是决定有利圈闭发育的主要因素,最终提出通过平北区古隆起周边断裂精细梳理是圈闭搜索与评价的重要方向。     

鲁西地块新生代断裂体系活动性与深部动力机制

根据野外观察分析, 综合前人研究成果, 对新生代时期鲁西地块的深、浅部构造特征、地震活动性以及动力学机制进行了分析。结果表明, 鲁西地块新生代浅表主体断裂构造格局为NW—NWW走向断裂构成的多米诺式组合, 震源机制解和野外观测揭示, 其具有左旋走滑性质, 并与NE向断裂共同控制了新生代盆地的形成和发育。地球物理资料揭示, 鲁西地块深部15~20km处存在一条缓倾滑脱带和大规模低速异常体, 浅表多米诺式断裂体系归并到该滑脱带, 表现为深浅部构造的脱耦性, 深部高低速异常体的过渡区域控制发育了鲁西地区两条NW向中强地震带。动力学成因上与太平洋板块俯冲作用导致地壳减薄、地幔上涌并在地幔楔中发生小尺度对流有关, 并造成了鲁西地块的隆起抬升。     

First results from the North Iceland experiment

Between June 2004 and September 2004 a temporary seismic network was installed on the northern insular shelf of Iceland and onshore in north Iceland. The seismic setup aimed at resolving the subsurface structure and, thus, the geodynamical transition from Icelandic crust to typical oceanic crust along Kolbeinsey Ridge. The experiment recorded about 1,000 earthquakes. The region encloses the Tjörnes Fracture Zone containing the Husavik–Flatey strike-slip fault and the extensional seismic Grimsey Lineament. Most of the seismicity occurs in swarms offshore. Preliminary results reveal typical mid-ocean crust north of Grimsey and a heterogeneous structure with major velocity anomalies along the seismic lineaments and north–south trending subsurface features. Complementary bathymetric mapping highlight numerous extrusion features along the Grimsey Lineament and Kolbeinsey Ridge. The seismic dataset promises to deliver new insights into the tectonic framework for earthquakes in an extensional transform zone along the global mid-ocean ridge system.     

莱州湾地区郯庐断裂带的构造特征及其新生代演化

郯庐断裂带中段分东西两支从莱州湾进入渤海,在莱州湾地区的构造特征与演化历史一直鲜为人知。通过对横穿研究区的两条地震测线的解释和分析,揭示了该区郯庐断裂带中段在研究区的构造差异,研究表明郯庐断裂带东西两支在该研究区表现出不同的断裂性质,西支断裂表现为正断层,东支断裂表现为走滑断层。郯庐断裂是本研究区的主控断裂,通过对本地区地层形态及其组合、断层的剖面形态和空间展布规律的深入研究,揭示了郯庐断裂带在莱州湾地区新生代以来的构造演化历史:古新世—始新世的伸展阶段、渐新世—中新世早期的挤压和右行走滑阶段、中新世中晚期至今的稳定发展阶段,这几个不同时期的演化阶段主要受太平洋板块运动的方向和速度变化的控制。