2011年1月19 日安庆ML4.8地震的震源机制解和深度研究

2011年1月19日在安徽省安庆市辖区与怀宁县交界处发生了M_L4.8级地震,引起安庆市及周边地区强烈的震感.为了更好地认识这次地震的发震构造,我们利用安徽省及临近几个省份区域台网的近震波形资料,首先通过hypo2000绝对定位得到震中位置;然后采用CAP方法反演了该地震的震源机制解和震源深度,并在此基础上结合P、sP、pP和sPmP等深度震相对震源深度进行了精确确定;最后,将反演得到的结果作为已知输入,利用F-K方法计算理论地震图,并与观测记录进行对比,以验证结果的可靠性.反演结果显示,这次安庆地震是一个带少量走滑分量的逆冲型地震,地震矩震级为M_W=4.3,最佳双力偶解为节面Ⅰ走向131°,倾角30°,滑动角29°;节面Ⅱ走向15°,倾角75°,滑动角116°,最佳震源深度为4~5 km,属于浅源地震.从震中和震源机制解来看,安庆地震极有可能发生在宿松-枞阳断裂上.     

闪电电场变化测量仪研究

分析了现有闪电电场变化测量仪存在的不足之处,提出了采用一台测量仪同时获得闪电电场快、慢变化特性的技术方案,通过对测量仪天线、电路、传输方式的优化,大大降低了系统的复杂程度,提高了可靠性;采用全介质光缆传输信号,可避免在信号传输过程中因电磁耦合带来的干扰;采用系统函数逆变换反演被测电场时域特性,既可省去一套专测电场慢变化的仪器,且弥补了以往"电场慢变化测量仪"性能的不足.测量结果表明,快变化测量系统的测量带宽为80 Hz~87.5 MHz.采用研制成的电场变化测量仪对自然闪电进行多次测量后,将反演运算得到的波形与实测波形对比,验证了所提方案的可行性和技术上的先进性.     

胶州湾不同季节浮游动物昼夜垂直移动规律初步研究

在胶州湾内设置连续站(36°5'54″N,120°15'20″E),分别于2006-2007年分春季、夏季、秋季、冬季四季进行垂直分段拖网,研究了胶州湾浮游动物垂直移动的规律。结果显示,浮游动物在不同季节显示不同的垂直迁移行为。同时,对该海域出现的优势种类的垂直移动规律进行了研究并分类,发现不同物种同一季节迁移方式不同,对于同一种类,在不同季节也表现出不同的迁移规律。因此,浮游动物垂直迁移规律不是一成不变的,由外界环境因子和内在因素共同作用决定。不同季节影响浮游动物垂直迁移的关键因子不同,其中春季、夏季、秋季三季主要影响因子是光照,冬季除了光照,还有温度、盐度和浮游植物密度。总体与温度和浮游植物密度正相关,与盐度负相关。对于不同种类,影响其垂直迁移的主要因子也不尽相同。     

Interferometry basics in practice: Exercises

The following exercises aim to learn the link between the object intensity distribution and the corresponding visibility curves of a long-baseline optical interferometer. They are also intended to show the additional constraints on observability that an interferometer has.This practical session is meant to be carried out with the ASPRO software, from the Jean-Marie Mariotti Center, but can also be done using other observation preparation software, such as viscalc from ESO.There are two main parts with series of exercises and the exercises corrections. The first one aims at understanding the visibility and its properties by practicing with simple examples, and the second one is about UV coverage.     

All you ever wanted to know about optical long baseline stellar interferometry, but were too shy to ask your adviser

I try to present a small view of the properties and issues related to astronomical interferometry observations. I recall a bit of history of the technique, give some basic assessments to the principle of interferometry, and finally, describe physical processes and limitations that affect optical long baseline interferometry and which are, in general, very useful for everyday work. Therefore, this text is not intended to perform strong demonstrations and show accurate results, but rather to transmit the general “feeling” one needs to have to not be destabilised by the first contact to real world interferometry.     

Titan's aerosols: Comparison between our model and DISR findings

Our model [Dimitrov, V., Bar-Nun, A., 1999. A model of energy dependent agglomeration of hydrocarbon aerosol particles and implication to Titan's aerosol. J. Aerosol. Sci. 30(1), 35-49] describes the experimentally found polymerization of C₂H₂ and HCN to form aerosol embryos, their growth and adherence to form various aerosols objects [Bar-Nun, A., Kleinfeld, I., Ganor, E., 1988. Shape and optical properties of aerosols formed by photolysis of C₂H₂, C₂H₄ and HCN. J. Geophys. Res. 93, 8383-8387]. These loose fractal objects describe well the findings of DISR on the Huygens probe [Tomasko, M.G., Bézard, B., Doose, L., Engel, S., Karkoschka, E., 2008. Measurements of methane absorption by the descent imager/spectral radiometer (DISR) during its descent through Titan's atmosphere. Planet. Space Sci., this issue, doi:10.1016/j.pss.2007]. These include (1) various regular objects of R=(0.035-0.064)×10⁻⁶ m, as compared with DISR's 0.05×10⁻⁶ m; (2) diverse low and high fractal structures composed of random combinations of various regular and irregular objects; (3) the number density of fractal particles is 6.9×10⁶ m⁻³ at Z=100 km, as compared with DISR's finding of 5.0×10⁶ m⁻³ at Z=80 km; (4) the number of structural units per higher fractals in the atmosphere at Z∼100 km is (2400-2700), as compared with DISR's 3000, and their size being of R=(5.4-6.4)×10⁻⁶ m will satisfy this value and (5) condensation of CH₄ on the highly fractal structures could begin at the altitude where thin methane clouds were observed, filling somewhat the new open fractal structures.     

Increasing the effectiveness of electrical resistivity tomography using γ11n configurations

A new array type, i.e., the γ_11n arrays, is introduced in this paper, in which the sequence of the current (C) and potential (P) electrodes is CPCP, and the distance between the last two electrodes is n times the distance between the first two ones and that of the second one and the third one. These arrays are called quasinull arrays because they are—according to their array and behaviour—between the traditional and null arrays. It is shown by numerical modelling that, in detecting small‐effect inhomogeneity, these configurations may be more effective than the traditional ones, including the optimized Stummer configuration. Certain γ_11n configurations—especially the γ₁₁₂, γ_113, and γ₁₁₄—produced better results both in horizontal and vertical resolution investigations. Based on the numerical studies, the γ_11n configurations seem to be very promising in problems where the anomalies are similar to the numerically investigated ones, i.e., they can detect and characterize, e.g., tunnels, caves, cables, tubes, abandoned riverbeds, or discontinuity, in a clay layer with greater efficacy than those of the traditional configurations. γ_11n measurements need less data than traditional configurations; therefore, the time demand of electrical resistivity tomography measurements can be shortened by their use.     

数字水准仪与光学水准仪对比观测研究

近年来,在高精度水准测量领域数字水准仪逐渐呈现出取代光学水准仪的趋势。本文通过实际观测实验,对比分析了两类水准仪的优势与不足。结果表明,光学水准仪相对较重,但性能稳定,而数字水准仪轻巧、操作方便,能很好地避免人为读数误差。在实际工作效率上光学水准仪占优,测量精度的稳定性好于数字水准仪。     

地形/均衡重力场模型构制及其拟稳分析

重力空白区数据填补的一个主要方法是基于地壳均衡理论进行的,该方法亦用于EGM系列模型的构建中.本文研究了地形数据在构制地形/均衡重力场模型中的应用,分析了补偿深度对Airy位模型和面凝聚位模型的影响,给出二者的最佳补偿深度分别为50 km和40 km.以纯卫星重力模型为参考,后者在前120阶的精度要高于前者,但在121~250阶的精度较低,组合模型精度高于单一模型精度.对地形/均衡地球重力场模型进行了EGM2008拟稳分析,研究了不同分辨率基准的拟稳效果,分析表明：30'分辨率的拟稳基准所得拟稳模型对应的阶方差与参考阶方差曲线直到360阶都有较好的一致性,以EGM2008为基准,其相对累计大地水准面高误差在140阶时为6.83cm,相对累计重力异常误差在220阶时为1.10 mGal.     

Sediment profile characterisation at contaminated and reference locations in the Windmill Islands, East Antarctica

Sediment profiles for pH, Eh, 28 elements, water and organic content are presented here for human impacted and reference locations in the Windmill Islands, East Antarctica. Variations in element concentrations are observed with increasing depth, especially at Brown Bay where the impact of past human activities is most pronounced in the top 10 cm. Spatial differences were observed between sediment profiles at reference and impacted locations and were largely explained by Pb variability in the top 5 cm. Median element concentrations from surface, middle and bottom regions of the sediment profile were compared to composite sample medians (no depth stratigraphy) for 11 elements at O’Brien Bay (reference) and Brown Bay (impacted). Pronounced differences were observed for Brown Bay, particularly surface and middle sections, implying that composite samples dilute the near surface anthropogenic signal by mixing with deeper uncontaminated sediment.