Discussion on moment tensor solution and seismogenic structure of Ruichang-Yangxin earthquake on 10 September 2011

Ruichang-Yangxin earthquake is another moderate earthquake in Yangxin-Jiujiang area since 2005 Jiujiang-Ruichang M5.7 earthquake. In order to more understand the seismic activities in this area, we study the moment tensor solution and the seismogenic structure of the Ruichang-Yangxin earthquake. Precise earthquake relocation shows that the mainshock occurred on the southwestern part of the NE-trending fault and aftershocks are distributed not only along the NE-trending fault but also along its conjugated NW-trending fault. By comprehensive analysis on the earthquake distribution, characteristics of isoseismal curve, focal mechanism, and regional structure characteristics, it is inferred that this earthquake is caused by the NE-trending Tanlu fault. In addition, it has close relationship with the conjugated NW-trending fault as well. Many researches have shown that the junction area is the earthquake-prone area, and should be paid more attention to. And our study also proves this viewpoint.     

Seasonal variability of phytoplankton community structure in relation to different nitrogen-phosphorus ratios in the southern coastal waters of Zhejiang, China

With the rapid development of economy and increase of population in the drainage areas, the nutrient loading has increased dramatically in the Changjiang estuary and adjacent coastal waters. To properly assess the impact of nutrient enrichment on phytoplankton community, seasonal microcosm experiments were conducted during August 2010–July 2011 in the coastal waters of Zhejiang Province. The results of the present study indicated that the chl a concentration, cell abundance, diversity indices, species composition and community succession of the phytoplankton varied significantly with different N/P ratios and seasons. Higher growth was observed in the 64:1 (spring), 32:1 (summer), 16:1 (autumn) and 128:1, 256:1 (winter) treatments, respectively. The values of Shannon-Wiener index (H′) and Pielou evenness index (J) were lower in the 8:1 and 16:1 treatments in autumn test, while H′ value was higher in the 128:1 and 8:1 treatments in winter test. A definite community succession order from diatoms to dinoflagellates was observed in the autumn and winter tests, while the diatoms dominated the community throughout the culture in the spring and summer tests.     

50-day Oscillation of Length-of-day Change

Variations of Earth’s rotation rate (length-of-day, LOD) occur over a wide range of time scales from a few hours to the geological age. Studies showed that the 50-day fluctuation exists in LOD change. In the present paper, the authors use wavelet technique to study the 50-day oscillation in LOD series. Temporal variations of the oscillation are presented in this work. After analyzing the axial component of atmospheric angular momentum (AAM) and oceanic angular momentum (OAM), the 50-day periodic signal is also found in atmospheric and oceanic motion with remarkable time-variation. Meanwhile, the 50-day oscillation of the axial AAM is in good consistence with that of LOD change. This suggests that the 50-day oscillation of LOD change is mainly excited by the axial AAM. Possible origin of the oscillation for Earth system is discussed in the end of this paper.     

古镇文化身份脆弱性的社会建构及其意义——多元话语分析模式的尝试

在建构主义研究范式的指导下选择多元话语分析方法,以江南水乡古镇周庄为案例地,对古镇文化身份的脆弱性进行社会建构分析。结果表明不同阶段政府旅游发展政策的改变、开发商的本质、传媒与专家系统的推力、游客凝视及对文化的态度、外来人群及其影响下原住居民的交往方式和价值取向共同建构了古镇文化身份脆弱性的形成过程。最后提出改造物质与生活环境、营建文化共同体、提倡理性交往等古镇文化身份脆弱性的治理对策,以期为文化遗产保护与可持续发展政策制定提供参考。     

1990—2010年黄河宁蒙段所处流域土地利用变化

以Landsat TM和ETM+遥感影像为基础数据源,应用地理信息系统技术,对黄河宁蒙段所处流域1990-2010年土地利用变化进行了监测,并结合气候变化、人类活动和政策因素探讨了土地利用变化的驱动力,初步分析了土地利用/覆被变化对流域水-沙关系的影响。结果表明：（1）20年来研究区建设用地面积增加了1 310.04 km²,耕地面积增加了611.15 km²,水域和草地面积分别减少了1 499.51 km²和474.93 km²;（2）20年来黄河宁蒙段所处流域土地利用变化速度经历了缓慢变化-显著变化-急剧变化的过程。各土地利用类型在后10 年（2000-2010年）的变化速度均比前10年（1990-2000年）大;（3）研究时段内草地和未利用地转化为林地,草地和耕地被开发为建设用地,未利用地和草地被开垦为耕地;（4）人类活动和政策因素是影响20年来土地利用变化的主要驱动因子,但人口数量的增加、经济的发展及环境政策的调整对研究区土地利用变化的影响更为显著;（5）1990-2010年流域耕地和林地面积分别增加了611.15 km²和543.19 km²,植被覆盖度由1990年的34.7%增加到2010年的40.8%。林地和耕地面积的增加均使得流域总蒸发量增加,灌溉用水增加,从而径流量减少,植被覆盖度的增加使得流域径流量和输沙量均降低。     

Geobiological processes of the formation of lacustrine source rock in Paleogene

Gypsum-salt rocks and coccolith calcareous shale are widely deposited in the lower part of the Paleogene Shahejie Formation in the Dongying Sag,Shandong Province.The gypsum-salt rock is believed to be formed during the earlier deposition in salt lake,while the overlying coccolith shale in saline lake with relatively low salinity.By comparing the lake environment and lacustrine microbial communities between ancient and recent lakes,cyanobacteria are regarded as the main representative of productivity during the formation of gypsum-salt strata series,with the annual productivity of 1500-2000 gC m-2 yr-1.Based on the research of ultramicrofossils in the calcareous shale,coccolith is considered as the main contributor to the productivity during the formation of calcareous shale.On the basis of statistic data of sedimentary rates,shale laminations,and coccolith fossils in each lamination,the quantitative value of productivity is calculated,with the annual productivity of 2250-3810gC m-2 yr-1(averagely 3120 gC m-2 yr-1).Statistic data of large amount of pyrite framboids indicate that the lower water column was persistently in sulfidic or anoxic conditions during the deposition of gypsum-salt strata series,but it changed to be dysoxic when the coccolith calcareous shale was deposited.Both of these water conditions are favorable for the preservation of organic matter.It is estimated that the organic carbon burial efficiency of the Lower Paleogene salt lakes and saline lakes of Dongying Depression is about 10%-15%,which is calculated and analyzed using the multi-parameter geobiological model.     

Upper mantle anisotropy and crust-mantle deformation pattern beneath the Chinese mainland

Over the past 10 years,the number of broadband seismic stations in China has increased significantly.The broadband seismic records contain information about shear-wave splitting which plays an important role in revealing the upper mantle anisotropy in the Chinese mainland.Based on teleseismic SKS and SKKS phases recorded in the seismic stations,we used the analytical method of minimum transverse energy to determine the fast wave polarization direction and delay time of shear-wave splitting.We also collected results of shear-wave splitting in China and the surrounding regions from previously published papers.From the combined dataset we formed a shear-wave splitting dataset containing 1020 parameter pairs.These splitting parameters reveal the complexity of the upper mantle anisotropy image.Our statistical analysis indicates stronger upper mantle anisotropy in the Chinese mainland,with an average shear-wave time delay of 0.95 s;the anisotropy in the western region is slightly larger(1.01 s)than in the eastern region(0.92 s).On a larger scale,the SKS splitting and surface deformation data in the Tibetan Plateau and the Tianshan region jointly support the lithospheric deformation mode,i.e.the crust-lithospheric mantle coherent deformation.In eastern China,the average fast-wave direction is approximately parallel to the direction of the absolute plate motion;thus,the upper mantle anisotropy can be attributed to the asthenospheric flow.The area from the Ordos block to the Sichuan Basin in central China is the transition zone of deformation modes between the east and the west regions,where the anisotropy images are more complicated,exhibiting"fossil"anisotropy and/or two-layer anisotropy.The collision between the Indian Plate and the Eurasian Plate is the main factor of upper mantle anisotropy in the western region of the Chinese mainland,while the upper mantle anisotropy in the eastern region is related to the subduction of the Pacific Plate and the Philippine Sea Plate beneath the Eurasian Plate.     

Effects of salinity on anatomical features and physiology of a semi-mangrove plant Myoporum bontioides

The effect of different concentrations of NaCl, 0, 100, 200, 300 and 400 mM, on the anatomical features and physiology of Myoporum bontioides was investigated. The photosynthetic rates (Pn) were significantly reduced by salt stress, with the lowest values at 400 mM NaCl. The content of malondialdehyde (MDA), proline and soluble sugar, as well as the activities of peroxidase (POD) and catalase (CAT) increased at the beginning, but became similar to the control as the experiment proceeded. The NaCl effect on superoxide dismutase (SOD) was different from the other parameters, with a significant reduction at 400 mM NaCl at Day 7. Salt glands were found in both upper and lower epidermis, and the ratios of the thickness of palisade to spongy mesophyll tissues increased with NaCl concentrations. The medullary ray was clearly damaged by NaCl at levels of 200 and 300 mM. These results demonstrated that M. bontioides could adapt to a relatively low salinity, and was not a halophilous species.     

Long-term differences in annual litter production between alien (Sonneratia apetala) and native (Kandelia obovata) mangrove species in Futian,Shenzhen, China

Annual litter production in alien (Sonneratia apetala) and native (Kandelia obovata) mangrove forests in Shenzhen, China were compared from 1999 to 2010. S. apetala had significantly higher litter production than K. obovata, with mean annual total litter of 18.1 t ha⁻¹ yr⁻¹ and 15.2 t ha⁻¹ yr⁻¹, respectively. The higher litter production in S. apetala forest indicates higher productivity and consequently more nutrient supply to the estuarine ecosystems but may be more invasive due to positive plant-soil feedbacks and nutrient availability to this alien species. Two peaks were recorded in S. apetala (May and October), while only one peak was observed in K. obovata, in early spring (March and April). Leaf and reproductive materials were the main contributors to litter production (>80%) in both forests. These results suggest that the ecological function of S. apetala and its invasive potential can be better understood based on a long-term litter fall analysis.     

Isotopic Characterization of Radioiodine and Radioxenon in Releases from Underground Nuclear Explosions with Various Degrees of Fractionation

Both radioxenon and radioiodine are possible indicators for a nuclear explosion. Therefore, they will be, together with other relevant radionuclides, globally monitored by the International Monitoring System in order to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty once the treaty has entered into force. This paper studies the temporal development of radioxenon and radioiodine activities with two different assumptions on fractionation during the release from an underground test. In the first case, only the noble gases are released, in the second case, radioiodine is released as well while the precursors remain underground. For the second case, the simulated curves of activity ratios are compared to prompt and delayed atmospheric radioactivity releases from underground nuclear tests at Nevada as a function of the time of atmospheric air sampling for concentration measurements of ¹³⁵I, ¹³³I and ¹³¹I. In addition, the effect of both fractionation cases on the isotopic activity ratios is shown in the four-isotope-plot (with ¹³⁵Xe, ^133mXe, ¹³³Xe and ^131mXe) that can be utilized for distinguishing nuclear explosion sources from civilian releases.