Aspects of growth in Arctic cod, Boreogadus saida (Lepechin 1773)

In June 1986- 42 young Arctic cod were caught in ice-covered waters of the Barents sea with dip-nets by scuba divers. From August to June 1987 the fish were kept at -PC and fed on frozen shrimp ( Pandalus borealis ). Length and weight were measured monthly. A fast weight increment of about 0.7% per day was observed in the autumn (Sept.-Nov.). In the winter (Jan.-Feb), the growth rate declined to 0.05% per day. However, daily food intake only decreased by 50% during these winter months. Since the fish were exposed to constant illumination in the aquarium, this growth experiment indicates that something else than light has a significant influence on growth in Arctic cod.     

Seismic attenuation in Faroe Islands basalts

We analysed vertical seismic profiling (VSP) data from two boreholes at Glyvursnes and Vestmanna on the island of Streymoy, Faroe Islands, to determine the magnitude and causes of seismic attenuation in sequences of basalt flows. The work is part of SeiFaBa, a major project integrating data from vertical and offset VSP, surface seismic surveys, core samples and wireline log data from the two boreholes. Values of effective seismic quality factor (Q) obtained at Glyvursnes and Vestmanna are sufficiently low to significantly degrade the quality of a surface reflection seismic image. This observation is consistent with results from other VSP experiments in the North Atlantic region. We demonstrate that the most likely cause of the low values of effective Q at Glyvursnes and Vestmanna is a combination of 1D scattering and intrinsic attenuation due to seismic wave‐induced fluid flow within pores and micro‐cracks. Tests involving 3D elastic wave numerical modelling with a hypothetical basalt model based on field observations, indicate that little scattering attenuation is caused by lateral variations in basalt structure.     

Azimuthal variation of Pg velocity in the Moldanubian, Czech Republic: observations based on a multi-azimuthal common-shot experiment

We study the azimuthal velocity variation of Pg waves in the Moldanubian, which is a crystalline segment within the Bohemian Massif in the Czech Republic. We use the data from a multi-azimuthal common-shot experiment performed as part of the ALP 2002 refraction experiment, complemented by profile refraction data from the CELEBRATION 2000 experiment. We analyze the travel times of waves recorded by 72 portable seismic stations deployed along two circles with radii of 35 and 45 km around a shot. The observed travel times display an azimuthal variation indicating anisotropy of 2%. The minimum and maximum velocity values are 5.83 and 5.95 km/s, respectively. The direction of the maximum velocity is N50°E. These values characterize horizontal anisotropy of the uppermost crust down to 3 km. The strength and orientation of uppermost crustal anisotropy in the Moldanubian is consistent with the overall upper crustal anisotropy in the entire Bohemian Massif. The high-velocity direction is roughly perpendicular to the present-day maximum compressive stress in the Bohemian Massif and Central Europe and coincides with the orientation of structures formed by the main Variscan tectonic events in the area. This indicates that the anisotropy is caused predominantly by alignment of textural elements and minerals in the rocks, which developed in early geological stages rather than by a preferred orientation of cracks or microcracks due to present-day stress. If the crack-induced anisotropy is present in the medium, then its strength should not exceed 1% and the cracks should be water saturated.     

Shear wave splitting in the Eastern Alps observed at the TRANSALP network

Data from the temporary TRANSALP seismic network were analysed to investigate the seismic anisotropy in the upper mantle beneath the Eastern Alps. We operated mostly short period and some broadband stations in a dense linear array, which transects the Eastern Alps at 12° E longitude. Recorded SKS and SKKS phases with different backazimuths were used simultaneously to calculate the splitting parameters of delay time and fast axis direction for each seismic station. While we found variations in the delay times between 0.8 and 2.0 s, the determined fast axis directions prove to be rather consistent along the profile (60°–70° N). They coincide well with the trend of the Eastern Alps, thus suggesting orogen-parallel flow in the upper mantle. Our findings support the earlier proposed idea that the Adriatic indenter which was forced northwards into the European plate during the late stage of the Alpine orogeny, triggered an escape movement to the less constrained Pannonian basin to the east.     

TRANSALP—Cross-line recording during the seismic reflection transect in the Eastern Alps

Cross-line recording formed a companion experiment of the TRANSALP seismic reflection transect through the Eastern Alps, conducted by partner institutions from Austria, Germany and Italy in three field campaigns in the period fall 1998 to fall 1999. Besides of the originally expected three-dimensional control for the north–south running main transect, additional information on seismic anisotropy and alternative images of crucial parts of the main transect could be gained.Conventionally processed sections along N–S running common-midpoint (CMP) binning lines confirm and strengthen the predominance of midcrustal reflective structures of the ‘Sub-Tauern-Ramp’ beneath and south of the Tauern Window. Velocity analysis of the first arrivals exhibit about 10% higher velocities in east–west propagating P-waves, compatible with texture-dominated rock anisotropy, recorded on cross-lines at the Tauern Window. Pre-stack depth migration of cross-line recordings shows dominant south dip of the Sub-Tauern-Ramp with easterly dip components and a sub-horizontal root zone of the Sub-Dolomites-Ramp.     

Local Seismic Events in the Area of Poland Based on Data from the PASSEQ 2006–2008 Experiment

PASSEQ 2006–2008 (Passive Seismic Experiment in TESZ; Wilde-Piórko et al. 2008) was the biggest passive seismic experiment carried out so far in the area of Central Europe (Poland, Germany, the Czech Republic and Lithuania). 196 seismic stations (including 49 broadband seismometers) worked simultaneously for over two years. During the experiment, multiple types of data recorders and seismometers were used, making the analysis more complex and time consuming. The dataset was unified and repaired to start the detection of local seismic events. Two different approaches for detection were applied for stations located in Poland. The first one used standard STA/LTA triggers (Carl Johnson’s STA/LTA algorithm) and grid search to classify and locate the events. The result was manually verified. The second approach used Real Time Recurrent Network (RTRN) detection (Wiszniowski et al. 2014). Both methods gave similar results, showing four previously unknown seismic events located in the Gulf of Gdańsk area, situated in the southern Baltic Sea. In this paper we discuss both detection methods with their pros and cons (accuracy, efficiency, manual work required, scalability). We also show details of all detected and previously unknown events in the discussed area.     

基于熵值-理想点法的泥石流危险度研究

泥石流危险度的划分是泥石流研究中的重点与难点,泥石流危险度的确定对于泥石流整体特征的把握具有十分重要的作用。采用熵值-理想点法建立了泥石流危险度划分模型,选取流域面积、主沟长度与泥石流沟相对最大高差等10个评价指标。利用现场3条泥石流沟作为工程评价对象,通过熵值法确定各评价指标的权重系数,并采用理想点法进行泥石流危险度的划分研究。根据模型分析结果,泥石流沟2与3属于高危险度(贴近度为0.79与0.83),泥石流沟1属于中危险度(贴近度为0.82)。泥石流危险度与现场情况及已有研究资料基本一致,证明了该法在泥石流危险度划分中的合理性与有效性。     

多尺度综合地球物理探测:揭示成矿系统、助力深部找矿——长江中下游深部探测(SinoProbe-03)进展

两个原因使我们必须开展深部探测.一是寻找深部资源,二是更好地理解形成和控制陆内成矿的深部动力学过程,预测新的矿集区.在深部探测专项、国家自然科学基金和地质调查项目资助下,作者在长江中下游成矿带及邻区开展了系统的多尺度、综合地球物理探测.包括:成矿带尺度的宽频地震探测及"廊带式"综合探测,矿集区尺度的骨干剖面探测和三维建模,矿田尺度的三维探测与反演模拟.探测结果在三个层次取得了一系列新认识和新发现,完善了相关探测方法技术.主要包括:揭示了成矿带岩石圈结构、深部过程及对成岩、成矿的控制,提出了成矿带形成的动力学模型,诠释了在狭窄的成矿带内形成大规模金属堆积的深部因素;揭示了典型矿集区地壳三维结构、组成和断裂分布,建立了矿集区三维结构模型和区域成矿模式,推断了主要控矿岩体、地层的空间展布,预测了新的找矿靶区;开展了"玢岩型"、斑岩型和热液型多金属矿床综合地球物理探测试验,总结了勘查模式,预测了深边部找矿靶区;提出了硬岩区反射地震数据采集设计、激发到接收的有效措施,探索了地震弱信号提取、噪声压制、静校正和偏移等处理新技术、新方法;提出了强电磁干扰区电磁去噪的数字形态滤波等技术,完善了二/三维带地形和考虑各向异性情况的电磁正反演技术.     

A comparative study of boron isotopes and trace elements of the marine foraminifers during the last glacial maximum and Holocene

Boron isotopic compositions in marine planktonic foraminifers can record changes in seawater pH and hence provide a new tool to reconstruct the changes of paleo-atmospheric PCO2.Here a comparative study was done on boron isotopes and trace element abundances of planktonic foraminifers,Globigerinoides sacculifer and Globigerinoides ruber from three tropical ODP sites,Site 806B,Site 664C and Site 999A.It is demonstrated here that G.ruber is a better species to be used for downcore boron isotope analyses on gl...