川滇地区重力异常的小波分解与解释

利用小波变换方法对四川云南及周围地区的布格重力异常进行分解. 在计算中选用具有正交完备性并有较好对称性及较高消失矩的小波函数把重力异常分解为两部分. 用功率谱方法对分解后异常进行分析,可知其分别表示地壳内部和更深部的密度变化. 两部分异常显示出川滇地区深部与浅部的构造差异. 浅层重力异常的密度填图表明:① 四川盆地地壳密度较高,松潘——甘孜造山带密度较低;② 康滇菱形块体的密度是不均匀的;③ 康滇菱形块体的边界断裂具有不同的密度特征,显示出不同的构造性质. 深部重力异常的密度填图显示出与浅部相似而又不同的密度分布特征,表明川滇地区浅部与深部构造作用有所不同,两者之间可能是不完全解耦关系. 本文结果还表明,地震分布不仅受断裂构造控制,也与深部密度变化有关.      

Impact of land use changes on surface warming in China

Land use changes such as urbanization, agriculture, pasturing, deforestation, desertification and irrigation can change the land surface heat flux directly, and also change the atmospheric circulation indirectly, and therefore affect the local temperature. But it is difficult to separate their effects from climate trends such as greenhouse-gas effects. Comparing the decadal trends of the observation station data with those of the NCEP/NCAR Reanalysis (NNR) data provides a good method to separate the effects because the NNR is insensitive to land surface changes. The effects of urbanization and other land use changes over China are estimated by using the difference between the station and the NNR surface temperature trends. Our results show that urbanization and other land use changes may contribute to the observed 0.12℃ (10 yr)- 1 increase for daily mean surface temperature, and the 0.20℃ (10 yr)- 1 and 0.03℃ (10 yr)-1 increases for the daily minimum and maximum surface temperatures, respectively. The urban heat island effect and the effects of other land-use changes mayalso play an important role in the diurnal temperature range change. The spatial pattern of the differences in trends shows a marked heterogeneity.The land surface degradation such as deforestation and desertification due to human activities over northern China, and rapidly-developed urbanization over southern China, may have mostly contributed to the increases at stations north of about 38°N and in Southeast China, respectively. Furthermore, the vegetation cover increase due to irrigation and fertilization may have contributed to the decreasing trend of surface temperature over the lower Yellow River Basin. The study illustrates the possible impacts of land use changes on surface temperature over China.     

一个简单陆气耦合模式中的绿洲-荒漠化效应

发展了一个简单的地气相互作用模式 ,讨论了不同气候和植被条件对绿洲消长的影响。结果表明 ,能使绿洲扩大的主要条件是低纬度、小尺度 ,并具有低水汽、较高温度的环境以及较小气孔阻力的植被。这一简单的理论分析对发展复杂的数值模式和对观测的布局有参考意义 ,对治理荒漠也有一定的启示。     

俄、蒙、中交界7.9级地震

2003年9月27日19时33分,在俄、蒙、中边界地区发生了Ms7．9地震,新疆阿尔泰地区强烈有感,地震造成经济损失7600万元人民币。文章对此次地震的基本参数、震源机制作了概述,并用遥感资料对地震的构造环境和破裂过程进行了初步分析。     

Genetic diversity and population structure of Eleutheronema rhadinum in the East and South China Seas revealed in mitochondrial COI sequences

Eleutheronema rhadinum is a potential commercial fisheries species and is subject to intense exploitation in China. Knowledge on the population structure of E. rhadinum in Chinese coastal waters, which is important for sustainable exploitation and proper resource management, is lacking. In the present study, the genetic diversity and population structure of E. rhadinum were evaluated using a 564-base pair fragment of the mitochondrial cytochrome c oxidase subunit I （COl） gene. A total of 76 specimens were collected from three localities around the East （Qidong and Zhoushan） and South China Seas （Zhuhai）. Among these individuals, nine polymorphic sites were detected and 1 l distinct haplotypes were defined. High levels ofhaplotype diversity （h=0.759i0.035） and low levels of nucleotide diversity （re=0.001 98i0.003 26） were observed in these populations, Hierarchical analysis of molecular variance （AMOVA） indicated that 96.72% of the genetic variation occurred within the populations, whereas 3.28% occurred among populations. No significant genealogical branches or clusters were recognized on the neighbor-joining tree. Intra-group variation among populations was significant （~0~t=0.032 85, P〈0.01）. These results suggest that E. rhadinum populations in the East and South China Seas have developed divergent genetic structures. Tests of neutral evolution and mismatch distribution suggest that E. rhadinum may have experienced a population expansion. The present study provides basic information for the conservation and sustainable exploitation of this species.     

A methodology to estimate the maximum offset and reflection imaging radius for a 2D/3D vertical seismic profiling survey

We have developed a straightforward and ray based methodology to estimate both the maximum offset and reflection imaging radius for multi‐layered velocity models, which can be used for a 2D/3D VSP survey design. Through numerical examples, we demonstrate that the presence of a high‐velocity layer above a target zone significantly reduces the maximum offset and reflection imaging radius. Our numerical examples also show that including in a migration VSP data acquired beyond a recommended maximum offset, radically degrades the quality of the final VSP image. In addition, unlike the conventional straight‐line based approximation that often produces an incorrect large reflection imaging radius, our methodology predicts the VSP imaging radius with more accuracy than does the conventional approximation.     

Coal price fluctuation mechanism in China based on system dynamics model

Natural Hazards - We analyze and identify the factors that influence coal price fluctuations and construct a system dynamics model of these factors. The simulation results show that the trend in...     

后“哥本哈根”时代的全球环境治理走向

2009年的哥本哈根世界气候大会并没有因为全球的关注和参与而成绩斐然。恰恰相反,因为美国的高调介入,它没有达成实质性的全球气候协议。这可能预示着后"哥本哈根"时代全球环境治理模式的到来:美国所倡导的"自下而上"的温室减排模式取代欧盟所倡导的"自上而下"的温室减排模式;以注重成本效益的经济减排模式取代风险预防的政治减排模式。世界也许将滑向一个容易但危险的方向。     

地震作用下多层剪切型组合结构的合理综合阻尼比取值探讨

对于组合结构,提出了一种新的基于单元瑞利阻尼模型的应变能振型阻尼比,并证明了其在特定整体阻尼矩阵下与强迫解耦法的等价性;推导了具有明确理论依据的综合阻尼比计算公式,并基于相应的应变能振型阻尼比得出了结构的刚度综合阻尼比和瑞利综合阻尼比。分别采用复振型分解法和振型分解法对算例结构进行了地震荷载作用下的弹性时程分析,结果表明,瑞利综合阻尼比对于以剪切变形为主的多层组合结构具有良好的计算精度和适用性。     

柴达木盆地东部石炭系页岩气储层渗流特征研究

页岩气是一种潜在资源量巨大的非常规天然气资源,页岩气藏具有多尺度的孔渗结构及多种渗流形态,研究页岩气藏储渗特征能够为页岩气的勘探开发提供理论支撑。该研究选取了柴达木盆地东部石炭系克鲁克组与怀头他拉组的页岩钻井岩心共5个样品,应用氩离子抛光扫描电镜实验与孔径分布测试(包括压汞法、氮气吸附法、二氧化碳吸附法)对页岩的孔隙结构特征进行定性定量测试。基于页岩气质量流量渗流模型,给出页岩表观渗透率与平均压力的关系。通过甲烷渗流模拟实验测定页岩的表观渗透率。从表观渗透率随平均压力的变化特征出发,分析页岩储层中的气体渗流规律。研究结果表明：页岩气的渗流形态包括滑脱流、扩散流及达西流。在低压情况下,渗透率低的页岩中以扩散流为主,其次为滑脱流。随渗透率的增大,渗流主要形式转变为滑脱流。当压力大于2 MPa时渗流形态以达西流为主,滑脱与扩散行为不明显。研究区内页岩微孔与中孔发育较多,达西渗透率与大孔的孔隙体积相关性较大,扩散流对表观渗透率的贡献与50 nm以下的孔隙孔体积比例有一定的相关性。低压下扩散流对表观渗透率的贡献较大,扩散流是一种非常重要的页岩气运移形式。