Site effects at a vertical accelerometer array near Paducah, Kentucky

The downhole vertical accelerometer array VSAP near Paducah, KY, consists of three-component accelerometers at the surface, the top of the McNairy Formation (−41 m), and the top of the Paleozoic bedrock (—99 m). The array is at the northern end of the Mississippi Embayment, and it was installed to verify the ground-motion modeling for the site, assuming a significant earthquake in the New Madrid Seismic Zone. Accelerograms from 4.2 and 2.0 m_b earthquakes were used to check aspects of the modeling pertaining to linear behavior of the soil column, and to review the soil column models derived by drilling and geotechnical methods and through the use of high-resolution P- and SH-wave seismic refraction in reflection techniques. Results of the study indicate that for the linear case the soil column models derived by the two techniques are equivalent, and that the most important boundary in the soil column, with respect to amplification of the ground motions, is the interface between the limestone bedrock and soil.     

跨孔条件下椭球模型的视电阻率异常特征

在跨孔条件下，利用积分方程法计算了孔区内外不同位置、不同产状的三维椭球体模型视电阻率异常。根据所得的典型数值模拟结果，借助视电阻率异常信息剖面图，对异常进行研究，总结了异常特征及其变化规律，并以此为基础分析和认识了其他模型的异常特征。     

塔里木盆地北缘库车盆地白垩系风成砂岩研究--以库车河剖面为例

库车盆地的早白垩世地层为一套干旱气候条件下的红层沉积，包括洪积扇砾岩、间歇性河流砂砾岩、风成细砂岩和粉砂岩、沙漠湖相紫红色泥岩等类型的沉积，组成一个较为典型的沙漠沉积体系。在库车河剖面，下白垩统红层中发育一些厚层至块状的“高能细砂岩和高能粉砂岩”，多为岩屑长石石英砂岩和长石岩屑石英砂岩。它们以良好的分选性和较高的结构成熟度、较细的粒度、较低的成分成熟度和大型交错层理的发育为特征，显示出较为明显的风成沉积特点。     

The role of diapycnal mixing for the equilibrium response of thermohaline circulation

Using a zonally averaged, one-hemispheric numerical model of the thermohaline circulation, the dependence of the overturning strength on the surface equator-to-pole density difference is investigated. It is found that the qualitative behavior of the thermohaline circulation depends crucially on the nature of the small-scale vertical mixing in the interior of the ocean. Two different representations of this process are considered: constant vertical diffusivity and the case where the rate of mixing energy supply is taken to be a fixed quantity, implying that the vertical diffusivity decreases with increasing stability of the water column. When the stability-dependent diffusivity parameterization is applied, a weaker density difference is associated with a stronger circulation, contrary to the results for a fixed diffusivity. A counterintuitive consequence of the stability-dependent mixing is that the poleward atmospheric freshwater flux, which acts to reduce the thermally imposed density contrast, strengthens the thermally dominated circulation and its attendant poleward heat transport. However, for a critical value of the freshwater forcing, the thermally dominated branch of steady states becomes unstable, and is succeeded by strongly time-dependent states that oscillate between phases of forward and partly reversed circulation. When a constant vertical diffusivity is employed, on the other hand, the thermally dominated circulation is replaced by a steady salinity-dominated state with reversed flow. Thus in this model, the features of the vertical mixing are essential for the steady-state response to freshwater forcing as well as for the character of flow that is attained when the thermally dominated circulation becomes unstable.Responsible Editor: Jin-Song von Storch     

The pelagic community of a gravel pit lake: Significance of Coleps hirtus viridis (Prostomatida) and its role as a scavenger

Coleps hirtus viridis was the dominant species of the planktonic ciliate community of Lake Fühlinger See (Germany) during the study in 1999 and 2000. Total ciliate densities ranged from 120 to 42,000 ind. l⁻¹ in 1999 and up to 8,000 ind. l⁻¹ in 2000. Coleps contributed up to 98% to both total ciliate abundance and biomass and made up an average of 64% of the total ciliate biomass. Oligotrichs (Rimostrombidium, Strobilidium) dominated the epilimnetic zone, whereas peritrich ciliates (Pelagovorticella, Vorticella) were predominantly located in the hypolimnion. The population maximum of Coleps changed locations from the epilimnion in early summer to the hypolimnion (up to 40,000 ind. l⁻¹) during stratification. High growth rates in the hypolimnion, presence of endosymbiontic algae and the ability to ingest detritus seem to be important for the success.Growth rates of Coleps in June were determined by Landry-Hassett dilution experiments in both the epilimnion and the hypolimnion. The instantaneous growth rates were similar in both layers (0.6 d⁻¹), but a distinctly higher instantaneous mortality was estimated for the epilimnion. These high loss rates may be due to grazing pressure by cladocerans.The significance of the histophagous feeding of Coleps was evaluated through an experiment using killed zooplankton. Parts of Daphnia magna were incorporated at rates of about 1,100 μm³ ind.⁻¹ h⁻¹ by Coleps without endosymbiotic algae and at rates of 500 μm³ ind.⁻¹ h⁻¹ by Coleps with endosymbionts. These high feeding rates support the conclusion that Coleps can use dead organic matter as an additional food source.     

A comparative study on the illite crystallinity and the clay mineral reflectance spectral index for subdividing the very low-grade metamorphic belt along the Lizhou-Hekou geological section in the Youjiang sedimentary basin, Guangxi, China

To examine the application potential of hyperspectral remote sensing techniques in classifying very low-grade metamorphic belts, the composition of clay minerals and the cyrstallinity of illite from mudstones were measured using XRD and VIS-SWIR (400-2500 nm) reflectance spectroscopy. Based on the illite cyrstallinity, Kubler Index (KI), the Early Triassic LuoLou Group and the Middle Triassic lower Baifeng Formation were classified as the lower Epizone with KI△2θ° ranging from 0.22 to 0.25, the upper Baifeng Formation as upper anchizone with KI△2θ°ranging from 0.26 to 0.33, and the Hekou Formation as lower anchizone with KI△2θ° ranging from 0.38 to 0.40. According to a KI△2θ° value of 0.43, it is possible that there may exist a local diagenetic zone in the upper strata. The illite cyrstallinity Kubler index and the metamorphic grade increase from the bottom to the top of the stratigraphic sequence. The metamorphic grade boundaries nearly match the stratigraphic boundaries, indicating a burial metamorphism nature for the stratigraphic sequence. From the bottom to the top of the sequence, the spectral absorption band center of clay minerals from fresh rocks is around 2200 nm. The absorption band centers change towards shorter wavelengths: the Luolou Group being at 2220 nm, the Baifeng Formation at 2217-2213 nm, the lower member of the Hekou Formation at 2214-2206 nm, and the upper member of the Hekou Formation at 2205-2197 nm. The spectral absorption band center of illite shows the same change pattern. These results indicate that very low-grade metamorphic belts can be subdivided using spectral indices of clay minerals, which are measured by using field portable spectroradiometers. However, it may not work well with satellite and airborne sensors.     

中国大陆科学钻探主孔2000米以上脆性变形构造应力场

在主孔2000米之内，存在复杂的脆性破裂系统和构造应力场。根据其充填物的特征，可划分为由石英、方解石和绿泥石等矿物充填的微破裂，发育石英、方解石等矿物薄膜或擦痕线理的微破裂和既无矿物充填、也无矿物薄膜的微破裂等3种不同类型的脆性应变现象，它们依次代表早、中、晚和深、中、浅3个不同构造层次的脆性变形。初步分析表明脆性变形阶段存在有以南东东-北西西向为主导的挤压作用、北东-南西向的区域挤压作用、南北向挤压作用和垂向伸展作用等4期构造应力场。郯庐断裂东侧的现代构造应力场在区域上具有极大的稳定性。在脆性和脆-韧性转换带，制约苏鲁高压-超高压变质带侵位的主导应力作用方式为自南东东往北西西方向的挤压，它在时间和空间上具有一定的稳定性。     

Slab behaviour and its surface expression: new insights from gravity modelling in the SE-Carpathians

We use lithosphere-scale gravity models to calculate gravity anomalies resulting from oceanic subduction, continental collision, slab steepening, delamination, and break-off. Local isostasy was assumed for determining vertical movements caused by mass changes related to these tectonic processes. Our results show that subduction is accompanied by basin subsidence on the upper plate caused by the heavy lithospheric root of the subducting slab. The basin evolution goes parallel with the slab evolution and shows considerable modifications when the processes at depth change (slab steepening, delamination, break-off). Characteristic gravity anomaly curves were acquired for the different tectonic scenarios. These curves together with other data (e.g. basin evolution on the upper and the lower plate) were used for the reconstruction of the tectonic evolution of the SE-Carpathians which includes Tertiary subduction and collision followed by slab steepening and delamination.     

竖向地震动强度包络函数的空间变化规律

利用SMART 1台阵三次地震记录拟合了各个测点在地震中的竖向地震动强度包络曲线及Amin 和Ang的强度包络函数中各模型参数值,分析了各模型参数的空间变化规律,建立了各模型参数随二维空间坐标及土层厚度变化的随机模型,为多点地震动合成中竖向强度包络函数的计算提供了理论依据。     

GPS monitoring of vertical ground motion in northern Ardenne–Eifel: five campaigns (1999–2003) of the HARD project

We present the HARD project of GPS monitoring of vertical ground motion in NE Ardenne and Eifel (western Europe). Its main purposes are to get a better insight into the present-day rates of vertical ground motion in intraplate settings and to identify the various causes of these motions. Since 1999, we have carried out yearly campaigns of simultaneous GPS measurements at 12 sites situated so as to sample the different tectonic subunits of the study area and especially to record potential displacements across the seismogenic Hockai fault zone. Five campaigns (1999–2003) have been processed currently. Key issues of the data processing with the Gamit software are discussed and first results are presented. Though temporally consistent in many cases, the obtained vertical motion rates are spatially highly variable. They are also much too high (several mm/year) to support a tectonic interpretation, and a long-term influence of groundwater level variations is proposed to account for the observed motions. This influence should be distinguished from seasonal variations and from inter-survey variations linked to the varying degree of soil and subsoil drying off during the successive spring surveys.