5 resultados para coda
em Chinese Academy of Sciences Institutional Repositories Grid Portal
Resumo:
本研究重点对云南哀牢山、无量山、永德大雪山以及老挝 Nam Kan 保护区西黑冠 长臂猿(Nomascus concolor)的鸣叫特征进行了分析研究,以探讨长臂猿鸣叫个体特异性 的发生机制及其在地理种群区分或亚种地位划分中的意义;同时对哀牢山平河西黑冠长 臂猿栖息地乔木结构进行了样方调查,揭示西黑冠长臂猿高海拔栖息地的乔木结构特 征,为后续行为学研究提供基础生态数据。 研究表明,云南省哀牢山平河(N 24°20′09.5″, E 101°17′16.1″, 海拔2600m)的黑 长臂猿栖息地有乔木57 种隶属于23 科37 个属;木质藤本植物9 种隶属于6 科8 属。 优势科主要为杜鹃花科(Ericaceae)、木兰科(Magnoliaceae)、山茶科(Theaceae)和 壳斗科(Fagaceae)植物。乔木的多样性指数、均匀度指数在沟底明显降低,而乔木1 层和2 层所占的比例以及木质藤本的平均多度均随着坡位的下降而升高。与其他地区的 长臂猿相比,哀牢山黑长臂猿的活动高度较低(10—22m),果实性食物种类较少。 西黑冠长臂猿的雄性鸣叫包括Boom 音节、aa 音节、弱调节音节、强调节音节和 coda 音节,Boom 音节只是一单独的条带状音节,结构最简单也最稳定;aa 音节、弱调 节音节、强调节音节和coda 音节的稳定性则呈现出依次增大的趋势。强调节音节和coda 部分的稳定性在总体没有显著差异,但在某些变量上coda 音节比强调节音节有显著更 高的稳定性。在此基础上,重点基于对coda 音节的分析,发现同一地点不同群体的雄 性西黑冠长臂猿个体之间存在非常显著的鸣叫特异性,并且同一地点不同群体的雄性个 体之间鸣叫的差异,显著高于不同地点间雄性个体间鸣叫的差异。这一发现表明西黑冠 长臂猿很有可能在有意识地通过鸣叫声音的调节,来增加与邻近群体间鸣叫的差异性, 并依靠这一行为识别邻近群的成年个体和陌生个体或新成年的未配对个体,这对具领域 性、配对的长臂猿来说具有显著的生态适应意义。基于对西黑冠长臂猿所有4 个亚种雌 雄个体鸣叫的逐步判别分析,结果表明西黑冠长臂猿明显分为3 个类群:1) 指名亚种 (N. c. concolor)和景东亚种(N. c. jingdongensis)为同一类群;2)滇西亚种(N. c. furvogaster)类群;3)老挝亚种(N. c. lu)类群,综合我们及前人的研究结果,我们认 为老挝亚种与其它三个亚种之间很可能已经达到了亚种分化的水平,滇西亚种也是如 此,但其有效性还值得进一步研究和探讨,而指名亚种和景东亚种间可能还没有达到亚种分化的水平。
Resumo:
Stress change is one of key factors in seismic nucleating and triggering; therefore for understanding and forecasting earthquakes, it is necessary to research on stress status and its changes in rocks. Propagating in underground structures, wave velocity and attenuation contain information on stress changes of the Earth’s interior. For a better understanding of relationship between seismic data and stress changes, modeling and ultrasonic test supply significant references. In this article, acoustoelastic theory is introduced to explain nonlinear elastic characteristics of rocks. Based on the acoustoelastic theory, a solid-fluid coupled model is given to calculate velocity under different stress for porous and liquid fulfilled rocks. Except for the stress-velocity relationship, effects of pore pressure induced stress changes on ultrasonic coda attenuation are also studied. Intrinsic attenuation quality factors are calculated for a comparison purpose. Finally, the relationship between elastic constants and stress changes is thoroughly investigated, a mixture model from two phases of Hooke media is introduced to explain the differences between dynamic and static moduli, a relation among wave length, wave velocities and elastic moduli considering dimension of microstructure, dimension and state of surface between phases is presented. The most important aspect of this work is exploring and establishing relationships between the seismic properties of rocks and changes of their stress conditions, which will have its application in earthquake forecast and seismic hazard.
Resumo:
The coda of seismic waves consists of that part of the signal after the directly arrivials. In a finite medium, or in one that is strongly heterogeneous, the coda is dominated by waves which have repeatedly sampled the medium. Small changes in a medium which may have no detectable influence on the first arrivals are amplified by this repeated sampling and may thus be detectable in the coda. Because of this, coda wave is widely used in detecting micro variations in medium。 In this paper, we give a general view of the theory and application of coda wave, especially coda wave interferometry. We focus on discussing the application of coda wave interferometry on data source of active situ experiment。 First, we apply coda wave interferometry in a short time period situ experiment which last for three days. We also apply the method of coda wave interferometry in a situ experiment which last for one month. Daily circle variations of seismic velocity around the experiment site were obtained, and we also observed that the velocity variations in the experiment site have a significant correlation with the environment factors, including air temperature, barometric pressure, solid earth tide and the level of rainfall. We find that the velocity variation during this period is up to 10-3. The relationship between velocity variation and changes in air temperature, barometric pressure and solid earth tide was analyzed with least square linear fitting .The velocity has no dependence on the air temperature. But velocity has a change of 10-6--10-7 when the barometer or earth tide change per Pa. Generally, we conclude the work and results of previous researchers, and we also display our works and results. We hopes to contribute to the future research of coda wave interferometry.
Resumo:
With the development of the technology of earthquake observation, more and more researchers work at many fields' of seismicity using seismic kinetic property, as the result, the study of attenuation has also made great progress, especially in the mechanism of the attenuation and the physical process. Aki put forward single back scattering theory to explain the forming of the seismic coda wave in 1969. Then, researchers started to develop the study in seismic scattering and attenuation. My thesis is also based on that theory. We assume that the Lg wave is a superposition fo high-mode surface waves, the coda of Lg is caused by scattering. Sato proposed Single Isotropic Scattering model (SIS model) to interpreted the scatter property, and he also formulated the geometrical spreading term. Then Xie (1988) developed the single spectral-ratio (SSR) method to obtain the Lg coda Q and the frequency dependent factor n. Later, he get to lateral images in the area of scatter ellipse. SSR method is explored and used in the study of Lg coda waves of regional earthquakes in my thesis. Choosing the earthquakes records with high ratio of signal-noise ,which were recorded at the stations from 1989 to 1999, we obtain the single trace Lg coda Q and its frequency dependent factor n. The results proved that SIS model is the reasonable model to explain the Lg coda wave, and SSR method also can be used to process Lg coda of regional earthquakes to get to the satisfied Lg coda Q. Based on the Lg coda Q we obtained using the former method, we explore the programs to inverse the regional Lg coda Q independently, and then make use of them to inverse the Lg coda Q of Beijing and adjacent area. The inversion result is satisfied. We conclude that the distribution of Qo (Q in lHz) is marked by the inhomogeneity, which is related to the tectonic structure: The value of Qo in uplift area, for example, Yanshan uplift, Taihang uplift, Luxi Uplift, is higher than the depression area, for example, Jizhong depression, Huanghua depression, and Jiyang depression, and the border between the higher Q area and lower Q area is very clear; Lg coda Q is also related to the velocity structure, higher velocity area is also with higher Q, lower velocity area is with lower Q; and higher heat-flow area is companied with lower Q. All in all, the value of Q reflects the difference of characteristics of lithofaces, porosity, the liquid content between the pores and heat flow. So, the Q value difference between uplift area and depression area reveals the difference of tectonic structure, lithology and physical character of the rock. So, the study of Lg coda Q is help to understand the earthquakes propagation mechanism through the inhomogenous medium, the cause of the coda, attenuation mechanism of the coda. Making use of the lateral images of Q, with velocity images, heat flow results, and other experimental result, we will be promoted to understand the complex structure of the crust, its inhomogenous character, and so on.