The Crust-Mantle Structure in Zhangbei-Shangyi Earthquake Area

The seismic data obtained from the wide angle reflection and refraction profiles that pass through Zhangjiakou area of Hebei Province were interpreted. Some conclusions drawn from the result are as follows: (1) The nearly EW-trending Zhangbei-Chongli crustal fault zone and WNW-trending Zhangjiakou-Bohai Sea deep crustal fault zone meet in the Zhangbei earthquake (Ms = 6.2) area; (2) At the intersection, the two deep crustal fault zones that stretch to the Moho and the discontinuities of interfaces within the crust form the path for large area basalt eruption in Hannuoba; (3) In the earthquake area, the local velocity reversal in the middle-upper crust and abnormal low velocity zone in the lower crust imply that the magmatic activity there is still fairly violent; and (4) The recent activity of Zhangjiakou-Bohai Sea deep crustal fault zone may be the main cause of the Zhangbei earthquake.     

Impact of fish farming on the distribution of phosphorus in sediments in the middle Adriatic area

During the last decade, intensive fish farming developed along the central Croatian coast, creating a need to study and evaluate its potential influence on unaffected sites. We considered phosphorus as an indicator of the influence of fish farming and investigated the distribution of phosphorus forms in sediment from several fish farms and marine areas of different trophic status in the middle Adriatic. Analyses of samples were performed with modified SEDEX techniques. Our results indicated that authigenic apatite phosphorus showed no significant differences among the investigated stations, while organic phosphorus concentrations reflected the trophic status of the station area. Below-cage sediment was characterized by enhanced fish debris phosphorus and low detrital apatite phosphorus concentrations, while sediment from an anthropogenically influenced bay showed the highest values of iron bound phosphorus species. Among the different P fractions, fish debris phosphorus proved to be the most sensitive indicator of the influence of fish farming on marine sediment.     

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哈萨克斯坦地震生物前兆现象观测和地震预测研究现状

从哈萨克斯坦地震生物观测的发展历史入手,简要介绍了哈萨克斯坦地震生物观测网的现状,地震生物观测的对象与方法,地震生物观测的信息采集内容等;归纳了利用地震生物行为资料开展地震预测的一般思路和方法;对比了中国和哈萨克斯坦对地震生物观测认识的差异等;最后,阐述了计划在新疆地区建立专业地震生物观测站的思路。     

Theoretical study on multi‐level source design

This paper studies aspects that influence the de‐ghosting performance of marine multi‐level sources based on a modified Johnson model. The normalized squared error between actual signature and its corresponding ghost‐free signature is introduced to evaluate the multi‐level source design. The results show that optimum depth combinations and volume combinations exist in the design. However, there is also some flexibility in the volume combination which makes it possible to optimize with respect to residual bubble oscillation. By considering both operational aspects and performance, we propose that three or four levels in a multi‐level source are reasonable. Compared to a horizontal source, a multi‐level source can be designed to reduce the notch effect, strengthen the down‐going energy and improve the energy transmission directivity. Studies of the influence of depth and firing time deviations indicate that a multi‐level source is more stable than a normal horizontal source in an operational environment.     

扇三角洲相与副层序关系的探讨

在湖泊中存在三种三角洲类型,即正常三角洲,辫状三角洲和扇三角洲。它们均由三角洲平原、三角洲前缘、前三角洲三部分所组成。陆相地层具有强烈的旋回性,只要将基准面看成海平面就完全可以运用层序地层学思路与方法研究陆相地层。扇三角洲相在断陷湖盆的陡坡一侧发育,通过与标准三角洲副层序模式对比,一个完整的扇三角洲序列可以划分出两个副层序。     

吐鲁番地区地震活动与应力场特征分析

对吐鲁番地区 1 90 0年以来地震活动的时空分布图像以及收集到的部分震源机制资料和1 999年 1月 30日托克逊 5.6级地震进行了分析。结果表明 :该区地震活动存在较明显的平静与活跃交替活动现象 ,两个活跃时段内地震活动的空间图像具有集中分布特征。中强震震源机制主压应力方位显示出北东向分布 ,说明区内地震活动的空间分布图像与区域应力场的作用密切相关。     

Changes in the radial growth of trees in relation to biogeomorphic processes in an old-growth forest on flysch,Czechia

Tree radial growth is influenced by individual tree abilities, climate, competition, disturbance regimes, as well as biogeomorphic processes – including biomechanical interactions between trees and soil. Trees are actively involved in hillslope dynamics, both responding to and affecting many (bio)geomorphic processes. Using dendrochronology, we studied feedbacks associated with tree–soil–landscape formation, specifically relationships between hillslope processes, biomechanical effects of trees in soils, tree microhabitat conditions and their morphological adaptations, in the flysch zone of the Carpathians. We visually evaluated stem shape, microhabitat conditions and the biomechanical effects of 1663 trees. Cores were taken in four growing directions from 224 individuals of European beech (Fagus sylvatica L.). In a set of 193 cross-dated beeches, average tree-ring widths and tree eccentricities in all directions were calculated and analysed in relation to the biogeomorphic impacts of trees. Some significant drivers of tree radial growth and sources of stem eccentricity were detected. The radial growth of trees on which deadwood was leaning was markedly limited. In contrast, trees with exposed roots expressed the highest growth rates. This clearly suggests that root exposure may not be an effect of ‘exogenous’ soil creep, but may rather result from individually intensifying tree growth due to fine-scale disturbance dynamics. The response of biomechanical tree–soil interactions in tree radial growth weakened with increasing stem diameter, reflecting the stabilizing role of larger trees. The significance of calendar year on radial growth suggests seasonality in the dynamic component of soil creep. Tree eccentricity was observed mainly in the downslope direction, which suggests a relatively complex effect of biomechanics on stem tilting. © 2020 John Wiley & Sons, Ltd.