南堡地区多期构造应力叠加模拟及断裂演化研究

南堡凹陷古近纪构造演化复杂,应力转换机制不够清晰,缺乏对多期构造应力叠加的研究,因此对局部构造带内断裂形成及演化规律难以做精细化解释。本文基于南堡3号构造勘探实践,采用平衡剖面技术与应力场数值模拟方法,对该区的伸展演化史与沙河街时期构造应力进行了模拟,建立了区域多期构造应力叠加模式,并分析了深部断裂体系的演化过程。研究结果表明:南堡地区经历了"强-弱-强-弱-强"的交替性伸展变化,在渤海湾盆地构造演化格局转折背景下,以Es_1~下沉积期为分界,区域伸展方向由NW-SE转变为N-S,使得Es_3-Es_2时期的NE向应力至Es_1期渐变为EW向展布,随之派生的EW向断裂也逐渐增多,主要断裂的扩展与演化能够很好地吻合各期差应力,性质与期次得到合理解释;渤海湾盆地东、西两侧主干断裂的右旋走滑运动造成的局部逆时针旋扭力场是导致南堡凹陷伸展转向的主要机制。     

The Taurewa Eruptive Episode: evidence for climactic eruptions at Ruapehu volcano, New Zealand

 The ca. 10,500 years B.P. eruptions at Ruapehu volcano deposited 0.2–0.3 km³ of tephra on the flanks of Ruapehu and the surrounding ring plain and generated the only known pyroclastic flows from this volcano in the late Quaternary. Evidence of the eruptions is recorded in the stratigraphy of the volcanic ring plain and cone, where pyroclastic flow deposits and several lithologically similar tephra deposits are identified. These deposits are grouped into the newly defined Taurewa Formation and two members, Okupata Member (tephra-fall deposits) and Pourahu Member (pyroclastic flow deposits). These eruptions identify a brief (<ca. 2000-year) but explosive period of volcanism at Ruapehu, which we define as the Taurewa Eruptive Episode. This Episode represents the largest event within Ruapehu's ca. 22,500-year eruptive history and also marks its culmination in activity ca. 10,000 years B.P. Following this episode, Ruapehu volcano entered a ca. 8000-year period of relative quiescence. We propose that the episode began with the eruption of small-volume pyroclastic flows triggered by a magma-mingling event. Flows from this event travelled down valleys east and west of Ruapehu onto the upper volcanic ring plain, where their distal remnants are preserved. The genesis of these deposits is inferred from the remanent magnetisation of pumice and lithic clasts. We envisage contemporaneous eruption and emplacement of distal pumice-rich tephras and proximal welded tuff deposits. The potential for generation of pyroclastic flows during plinian eruptions at Ruapehu has not been previously considered in hazard assessments at this volcano. Recognition of these events in the volcanological record is thus an important new factor in future risk assessments and mitigation of volcanic risk at Tongariro Volcanic Centre. Received: 5 July 1998 / Accepted: 12 March 1999     

夏季东北亚阻塞形势维持时的天气尺度波

利用NCEP/NCAR逐日资料，分析了一次夏季东北亚阻塞形势维持期间(1991年6月27日至7月16日)高频波活动强弱的分布和传播的特征，发现在阻塞高压上 游的巴伦支海上空有明显异常的高频波活跃区，从该活跃区和位于东北大西洋的常年活跃区，高频波不断东传，传到东北亚时，变弱消亡。据此，作者推测高频波的能量传给了阻塞形势，使阻塞形势得以维持。利用Eu矢量分析的高频波能量传播也表明了这一点。此外，利用Eu和Ev矢量讨论了高频波对纬向平均流和经向平均流的反馈强迫作用。结果表明，高频波的强迫作用使得时间平均纬向流在急流分支处呈减弱的趋势。高频波对时间平均的经向流反馈强迫作用更加明显，这种强迫使得急流在阻塞高压的上游产生分支，而在下游产生南北分支气流的汇合。最后，分析了高频波和低频波对热量的南北输送，表明在阻塞期间高频波在东亚地区对流层顶附近产生非常清楚的向北热量输送(冷空气向南输送或暖空气向北输送)，而低频波(可用来表示阻塞流型)的向北热量输送作用表现在对流层中下层，相对来讲不明显。     

MIS 3晚期东亚季风强度和DO事件年龄

基于神农架山宝洞石笋(SB46)的9个230Th年龄和326个氧同位素数据,建立了末次冰期32.2～26.7kaB.P.和17.0～15.4kaB.P.的东亚季风降水序列。该序列和同一洞穴全新世石笋记录的对比发现,在MIS3晚期东亚季风区可能存在极强夏季风降水事件,相当于全新世季风强度,可能与岁差旋回太阳辐射及海陆水汽潜热释放增强有关。与葫芦洞石笋δ18O记录和格陵兰冰芯δ18O记录对比表明,东亚夏季风千年尺度气候振荡与高北纬地区海-气快速重组存在遥相关效应。山宝洞石笋年龄与葫芦洞石笋和格陵兰冰芯时标(SS09sea)在定年误差范围内基本一致,但山宝洞石笋与冰芯记录在DO事件的年龄、波形和持续时间上更为一致,不仅进一步说明了低纬季风气候与极地气温同步变化,而且有效地弥补了葫芦洞记录在这一时段的不足。     

东南沿海地震带20世纪活跃幕划分及活动周期分析

探讨了东南沿海地震带20世纪以来在时间分布方面存在的密集－平静相互交替的丛集现象。 对以往按地震能量释放的分布划分出的活跃—平静幕数目不等的多种结果; 对东南沿海地区54次M≥43/4地震的时间间隔序列, 在使用有序样品聚类分析中的“离差平方和”法及误差函数法, 从误差随分段数增加而减少的拐点值及误差函数比值认为四段活跃幕划分是合理的。 从 1943 年之后, 计算得出的东南沿海地区中强以上地震序列的时间变异系数δ值为1.2 , 明显处于丛集状态。 对东南沿海地震区20世纪以来四个地震活跃幕中, 其丛集非线性时间结构演化幂指数, 即各幕地震的累积频次与发震系统内部时间的关系基本符合为N=ct^d。 4个活跃幕的演化幂指数d变化范围分布在0.7~0.8。 东南沿海地震区20世纪以来M6.0以上的强震也基本符合该关系式。 只是其活跃幕演化幂指数d为 0.47 。     

涟源凹陷流体包裹体特征与天然气成藏

涟源凹陷属于典型的改造型盆地,是湘中坳陷最有利的含油气凹陷之一。应用流体包裹体分析技术,并结合盆地构造演化和圈闭发育史、烃源岩主要生、排烃史,对改造型盆地涟源凹陷主要目的层石炭系储层中流体包裹体特征及气藏形成时间和期次进行了分析。结果表明,研究区存在两种类型流体包裹体,第一类为单一液相或气/液比小于15%的气液两相盐水包裹体,第二类为气液两相含烃盐水包裹体,单一液相包裹体大小一般3~4μm,其它包裹体大小一般1~7μm;流体包裹体特征反映出该区气藏成藏期有两期,即第一期天然气注入时温度120.8~126.2℃,对应成藏时间为早三叠世,第二期天然气注入时温度154.4~169.7℃,对应成藏时间为晚三叠世,其中主要成藏期为晚三叠世。     

A meteorological analysis of ozone episodes using HYSPLIT model and surface data

Ozone episodes (> 100 ppbv) were observed frequently in Jinan, an urban site located between the highly polluted Yangtze Delta and Beijing–Tianjin region in East China. In this study, the ozone episodes observed in 2004 were analysed using the Hybrid Single-particle Lagrangian Integrated Trajectory (HYSPLIT) model and surface meteorological data, as well as Air Pollution Index (API). The meteorological conditions of episode days and non-episode days were compared and examined, and categorization of 6 groups of backward trajectories was performed. The results show that, most episodes were caused by local photochemical production (e.g., induced by sufficient sunshine duration and high temperature) and pollutant accumulation (e.g., induced by little rainfall and low wind speed), and transport of pollutants from the highly polluted regions could significantly influence the air quality at the site, especially from Yangtze Delta region. In addition, three typical ozone episodes were analysed using HYSPLIT model to infer any long-distance transport and surface meteorological data to infer the local ozone production potential. At last, the functions and inadequacies about the usage of HYSPLIT model combined with surface meteorological data for the analysis of photochemical pollution were discussed.     

A Reconstruction for the Late Paleozoic Tectonic Evolution of the Tekes Daban Area, Western Tianshan Mountains: Evidence from Unconformities

The identification of unconformities is the key to reconstructing tectonic evolution, revealing crust movement and establishing tectonic cycle. For a long time, there were some controversial issues on the episodes of Variscan cycle (especially on the period of Carboniferous-Permian stages) of the Tianshan area. The essential questions fall on the numbers and property of unconformities in this area, for example, in the western Tianshan area. Previous research only recognized three or four fold movements. Detailed regional geological mapping of 1:50000 in the Tekes Daban area, western Tianshan have allowed us to characterize the seven unconformities within the Carboniferous-Permian strata and understand its implications for tectonic reconstruction of the Tianshan orogen. Seven angular unconformities, which indicate that seven tectonic episodes occurred in the Late Paleozoic Period, were identified in this area. Therein, the newly discovered unconformities based on the angle-unconformity between the Dongtujinhe and Keguqinshan Formations, and angle-unconformity between the Wulansayi and Wulang Formations, respectively indicates the Tekes episode and Gongliu episode. The unconformity between the Dongtujinhe and Yishijilike Formations is angle-unconformity instead of parallel unconformity indentified by previous research, so the former Bogda ascending can be revised as Bogda movement. Therefore, these newly identified seven episodes, including the Tekes episode, suggest that there are seven tectonic movements in the Tianshan area at least. This has significant implications for reconstruction of the Late Paleozoic tectonics in the Tianshan Area, NW China     

华北北部强震活动性研究

华北北部是指39.0—41.0°N,114.0—117.0°E的区域,其历史强震活动呈现出百年尺度的轮回(M_s≥6 3/4)和10年尺度的幕式(M_s≥5.0)的不均匀过程。应用上述特征和强震活动重复性的伯努利模型,预期在2005年前该区发生6级地震的可能性很大。     

布莱克（Blake）负向极性幕研究的新进展

本文概述了国内外布莱克负向极性幕的研究历史与现状，报导了许家窑旧石器遗址上更新统湖相剖面布容正向极性时（带）中负向极性段的位置、时间及剩磁特征。根据剖面上铀子系法测定的年代值和该负向的转换性质，笔者确认该负向极性段时间上对应于布莱克负向极性幕。