Neogene volcanism and Holocene earthquakes in the Tanlu fault zone, eastern China

In this paper, we study the relationship between Neogene volcanism and Holocene earthquakes in the Tanlu fault, eastern China. We find that fault segments through which Neogene and Quaternary magma have extruded do not show Holocene slip because they are covered by unfaulted basalts. In contrast, fault branches that are away from the Quaternary volcanic centers display Quaternary faulting and are responsible for earthquakes as recorded both historically and geomorphologically. Therefore, magma intrusion appears to modify fault activity in two different ways: (1) within the faults, the cooling magma serves as a cohesion or barrier, welding the faults so that they become stronger in resisting slip; (2) beneath the faults, the upwelling magma promotes slip of faults above the magma body, and hence generation of earthquakes. Physically, the first case results from contraction of the cooling magma, which causes a relative increase in fault-normal stress so that the fault failure resistance is enhanced. The second case results from the upward dynamic force and the heat brought in by the magma body, both of which cause the effective fault-normal stress to decrease so that the fault failure resistance is reduced. That could explain why earthquakes occur on faults bypassing the volcanic centers as typified in the Yishu fault zone and in the regions where heat flows are relatively high as shown in the Bohai Bay area.     

锦屏Ⅰ级水电站坝区岩体结构面特征研究

本文根据锦屏Ⅰ级水电站坝区体结构面野外调资料，对坝区结构面优势方位、间距、张开度、连通率、隙间充填物及形态特征进行了分析，为坝区岩体分类及其物理力学参数的确定提供了重要依据。     

沉积物捕获器在海岸与陆架沉积动力研究中的应用:以罗源湾和台湾海峡为例

运用时间序列的沉积物捕获器对海岸与陆架海域沉降颗粒物进行采集,估算沉降通量,并运用多学科综合研究手段分析沉降颗粒物的来源、组成、时空变化及控制因素,可以为海岸与陆架沉积动力过程的研究提供新的研究手段。福建罗源湾的实验表明,夏季罗源湾潮下带小潮至中潮期间的沉降通量为133.20~256.18g/(m2·t);由中潮向大潮变化期间单个潮周期的沉降通量明显增大,台风过后的大潮期间的沉降通量为373.99~590.51g/(m2·t);台风显著影响期间的沉降通量为746.34g/(m2·t);粒度分析及水动力观测结果显示,观测期间罗源湾潮下带沉降颗粒物主要来源于海底沉积物的再悬浮。台湾海峡西北部内陆架海域的实验研究表明,该海域近底部悬浮颗粒物沉降通量最大值为13.34g/(m2·d),由小潮向中潮沉降通量逐渐增大,这主要是由于近底部温盐跃层层位上移,近底部垂向混合作用增强,致使底部再悬浮沉积物向上扩散,并最终被沉积物捕获器捕获。沉积物捕获器可以接收到再悬浮沉积物,结合底部边界层过程的观测研究,可以深入认识海底沉积物的侵蚀、沉降及埋藏过程,在研究海岸与陆架区沉积动力学、泥质区沉积记录的形成过程与保存潜力中扮演着十分重要的角色。     

换道概率对交通系统动能的影响

基于跟车模型的特点,提出了跟车模型的动能变化公式,利用该公式研究换道概率对各车辆动能的影响.数值实验结果表明,换道概率和相对速度对各车辆动能产生较大影响,但换道概率和相对速度会分别降低其动能变化频率和幅度.此外,系统增加的平均动能会随着系统最大换道概率的增加而降低.     

Diurnal variation of nitric oxide emission flux from a mangrove wetland in Zhangjiang River Estuary,China

The diurnal variation of nitric oxide (NO) emission fluxes from a Kandelia obovata and Avicennia marina mangrove wetland were studied in the Zhangjiang River Estuary Mangrove National Nature Reserve using a dynamic chamber-based technique and a chemiluminescent analyzer. Results from field experiments show that NO emission from K. obovata and A. marina sampling sites reached maximal values of 1.07 ng N m⁻² s⁻¹ and 1.23 ng N m⁻² s⁻¹, respectively after the night tide. Meanwhile NO emission maintained at a steady lower level in daytime for both wetland sites. In laboratory experiments, NO emission from the mangrove wetland soil samples treated with simulated tides in the darkness exhibited higher values than those in the light, therefore it seems that tides and darkness could increase NO emission from mangrove wetlands, while intensive light, high temperature, and dryness in the daytime decreased NO emission. Compared with K. obovata soil samples, the diurnal average NO emission rate of the A. marina site was significantly higher, which was closely related to relatively higher diurnal average CO₂ emission rate, soil available nitrogen content and soil net nitrification rate of the A. marina site. Moreover, soil samples of the A. marina site were more responsive to simulated tides and the addition of nitrogen than those of the K. obovata site.     

Experiments on the reflection coefficients of a detached breakwater in a directional wave field

Results of estimating the directional wave fields in front of a detached breakwater are presented here in this paper. Two of non-phase-locked methods, i.e., the Maximum Likelihood Method (MLM) and the Extended Maximum Entropy Principle Method (EMEP), were adopted for the purpose. In general, the latter outperforms the former. It is shown that the reflection coefficients decrease with increasing distances away from the detached breakwater, and within four wavelengths from the detached breakwater, the rate of the decrease is faster for wave fields having larger directional spreads. When the measuring distance is more than four wavelengths away from the detached breakwaters, the reflection coefficients tend to reach to a constant value. It is shown that, with the use of the non-phase-locked EMEP method, the effective region can be extended, as compared with the results of Huntley and Davidson [J. Waterw. Port Coast. Ocean Eng. 124 (1998) 312].     

Preface to the special issue “Tectonics and depositional infilling of western Pacific marginal sea”

Marine Geophysical Research -     

南海北部底层沉积物捕获器中海雪和生物粪粒组成及来源探究

Sediment traps are an important tool for studying the source, composition and sedimentation processes of sinking particulate matter in the ocean. An in situ observational mooring(TJ-A-1) is located in the northern South China Sea(20.05°N, 117.42°E) at a water depth of 2 100 m and equipped with two sediment traps deployed at 500 m and 1 950 m. Samples were collected at 18-day intervals, and 20 samples were obtained at both depths from May 2014 to May 2015. Large amounts of fecal matter and marine snow were collected in the lower trap. The fluxes of marine snow and fecal pellets exhibited a fluctuating decrease between May 2014 and early August 2014 and then stabilized at a relatively low level. Scanning electron microscopy observations revealed that the main components of the marine snow and fecal pellets were diatoms, coccolithophores, radiolarians, and other debris, all of which are planktons mostly produced in photic zone. Used in conjunction with the particle collection range estimates from the lower trap and data on ocean surface chlorophyll, these marine snow and fecal pellets were related to the lateral transport of deep water and not vertical migrations from overlying water column. Moreover, the source area might be southwest of Taiwan.     

Spatial and temporal variations of mesozooplankton in the Pearl River estuary, China

This paper examines spatial and temporal variations of mesozooplankton abundance, biomass and community structure during three cruises of July 2002 (summer), January 2003 (winter), and April 2003 (spring) in the Pearl River estuary, China. Zooplankton abundance and biomass fluctuated widely and showed distinct heterogeneity in the Pearl River estuary. A total of 154 species were identified during three surveys. The number of zooplankton species richness was strongly linked to salinity. Hierarchical cluster analysis identified three zooplankton groups during this study. Estuarine, neritic and pelagic groups corresponded to the upper, middle and lower reaches in the Pearl River estuary. The difference among groups could be mainly ascribed to changes in the relative contributions of the dominant species. The fluctuations in the zooplankton abundance, biomass and community structure were determined by the interactive effects of freshwater inflow, tidal and coastal currents, chlorophyll a, salinity and temperature. Significant spatial variability in the distribution of zooplankton species, abundance and biomass can be ascribed to the virtual presence of a horizontal gradient in salinity.     

国际地球自转服务(IERS)评介

回顾了建立国际地球自转服务(IERS)的历史过程,简述了IERS机构各部门的设置及其作用。着重介绍了IERS重建的理由和过程以及新IERS机构的组成。最后给出IERS成果对现有科学研究的作用和意义。