短脉冲激光在实验室天体物理方面的研究进展     

孙嘉宁  袁大伟  王菲鹿 《天文研究与技术》2021,(2):248-254

随着啁啾脉冲放大技术(Chirped Pulse Amplification,CPA)的飞速发展,激光功率密度实现了飞跃式的提升,利用短脉冲激光开展实验室天体物理研究的条件日趋成熟。短脉冲激光与靶相互作用可以产生相对论粒子(正负电子、质子、中子等)和高能电磁辐射(X射线、γ射线),这些粒子和辐射的产生过程与天体中的某些物理现象相对应。介绍了利用短脉冲激光开展实验室天体物理的研究进展,重点介绍了核天体物理、空心离子光谱学、相对论无碰撞冲击波以及等离子体状态诊断等。  相似文献   

海洋效应对中国沿海地磁观测影响——以广州台站为例   总被引：2，自引：1，他引：1       下载免费PDF全文

李建平  翁爱华  李世文  杨悦  唐裕  张艳辉 《地球物理学报》2018,61(2):649-658

以广州台站为例，研究海洋效应对中国沿海地磁观测C-响应的影响.海洋效应的三维正演模拟采用球坐标系下交错网格有限差分方法，假设磁层环形电流源，正演电阻率结构模型采用"地表3-D电导+1-D层状背景"复合模型.数值模拟结果表明，中国地区沿海C-响应受海洋效应影响明显.在空间上，沿海岸线方向，受海洋效应影响，单周期的C-响应由无海洋效应的常值变形为平行于海岸线的等值线密集梯度带；在垂直海岸方向，海洋效应影响向内陆减小，其影响可达哈尔滨-贵阳一线.海洋效应影响采用比值法进行校正，以广州台站为例，在比值曲线上发现海洋效应对C-响应的影响最大周期可达20天左右，并且就中国沿海而言，相对全球平均一维模型，利用中国地区平均一维电导率模型作为背景模型的海洋效应校正结果更加合理.进一步对广州台站海洋效应校正前后的C-响应进行了1-D反演，由于校正前的C-响应在小周期时受海洋效应特别大，直接反演无法拟合数据；但校正后反演拟合明显变好，得到的1-D导电模型表明广州地区上地幔及地幔转换带的电阻率比中国平均电阻率高约一个量级，推测中国华南地区南部的地幔转换带可能处于相对冷的环境，该模型可能成为菲律宾海板块西向俯冲并滞留到华南大陆下方地幔转换带的电性证据.  相似文献   

基于背景噪声研究青藏高原东北缘瑞利波相速度和方位各向异性   总被引：2，自引：1，他引：1       下载免费PDF全文

王琼  高原 《地球物理学报》2018,61(7):2760-2775

本研究收集了甘肃、青海、宁夏等118个宽频带数字地震台站的连续波形资料，利用噪声互相关，经过计算和筛选，在5~38 s范围内，共得到5773条瑞利波相速度频散曲线.然后采用1°×1°的网格划分，反演获得青藏高原东北缘相速度和方位各向异性分布.结果表明：短周期8~12 s内，鄂尔多斯从低速异常变为高速异常；该周期范围内各向异性结果与区域断裂走向有很好的一致性.18~25 s周期内，祁连地块、松潘-甘孜地块、羌塘地块低速异常范围逐渐变大，随周期增加地壳低速异常与人工探测结果相符；鄂尔多斯表现为速度随周期增加逐渐变大，说明其中下地壳速度相对偏高，不存在低速异常；该周期范围内的各向异性特征表现为，祁连地块和松潘甘孜地块大致呈NW-SE方向，而青藏高原内部快波方向显示了顺时针旋转的形态.在30~35 s范围内面波速度主要受莫霍面深度和莫霍面附近介质速度的影响，与地壳厚度分布有非常好的吻合.综合不同方法获得的各向异性研究结果，支持印度-欧亚板块的碰撞使青藏高原东北缘地壳发生缩短和逐渐隆升的观点，认为整个岩石圈的垂直缩短变形是青藏高原东北缘的主要形成机制.  相似文献   

Study on the Moment Magnitude of Small and Moderate Earthquakes Located in the Inner Mongolia Region     

Liu Fang  Zhang Fan  Li Bin  Na Re 《中国地震研究》2018,32(1):53-63

Based on digital seismic waveform data from Inner Mongolia Digital Seismic Network, the source spectrum parameters of 182 small and moderate earthquakes from January, 2009 to September, 2016 are derived, and the seismic moment M₀ and moment magnitude M_W of the earthquakes are calculated. The M_L-M_W relationship and the relationship between stress drop and magnitude are obtained using the linear regression method. It is clear that incorporating the moment magnitude into the seismic quick report catalog and the official earthquake catalog can enrich earthquake observation report content, thus providing better service for earthquake emergency and earthquake scientific research.  相似文献   

SIMULATION STUDY OF ROAD-CUT EFFECTS ON SLOPE STABILITY     

CHEN Xiao-li  WANG Ming-ming  ZHANG Ling 《地震地质》2018,40(6):1390-1401

Landslides and rock falls along the highway are common geological hazards in Southwest China. As an influencing factor on potential landslides behavior, roads or distance to roads have been successfully used in landslide susceptibility assessments in mountainous area. However, the relationship between the road-cut and the slope stability is not clear. Therefore, we performed two-dimensional slope stability calculation using the general limit equilibrium (GLE)method incorporated in the software SLOPE/W of GeoStudio for stability analysis of slopes. Our studies show that the man-made roads influence on the slope stability mainly exists in two ways:One is to create a new steep slope, which will result in rock falls and shallow landslides along the roads; the other is to influence the stability of the original slope, which will result in comparatively huge landslides. For the latter, our simulation study reveals that the road location, namely at which part of a natural slope to construct a road is important for the slope stability. For a natural slope with a potential slip surface, if a road is constructed at or near the slope toe where the potential slip surface surpasses, it will greatly degrade the slope's factor of safety (Fs) and make the slope unstable; however, if a rode-cut is near the top of the slope, it will increase the slope's Fs and make the slope more stable. The safety location is different for different slope angle, steeper slope needs a higher location for a safety road-cut in comparison with gentle slopes. Moreover, the slope stability decreases when loading a seismic force and it varies with the slope angle. Firstly, the Fs decreases when the slope angle increasing, and when the slope angle reaches 45°, the Fs then becomes greater with the slope angle increasing.  相似文献   

Precise Location of Earthquakes at the Eastern Boundaries of the Sichuan-Yunnan Rhombic Block     

Fu Ying  Hu Bin  Long Feng  Wang Shiyuan 《中国地震研究》2018,32(4):470-481

Based on the seismic station data sets from Sichuan and Yunnan provinces, we employed a multi-step seismic location method (Hypo2000 + Velest + HypoDD) to precisely locate the 7,787 earthquakes that occurred during 2010-2015 along the eastern boundaries of the Sichuan-Yunnan rhombic block, namely from southern Dawu to the Qiaojia segment. The final results show that location precision is greatly advanced and epicenter distribution exhibits good consistency with the linear distribution of the seismic faults. Earthquake distribution is quite intensive at the intersection region in the southern segment of the Xianshuihe fault, the Anninghe fault zone, the Xiaojinhe fault zone and the Daliangshan fault zone to the east. The depth profile of seismicity shows a clear stepwise activity along the active seismic fault zones. The profile crossing the faults of the Xianshuihe, Anninghe, and Daliangshan presents a complex interaction among faults near the multiple faults intersection region, Shimian, where the earthquakes are obviously divided into two groups in depth. Earthquakes are very rare at the depth of 15km-20km, which is consistent with the region of the plastic rheology between 14km-19km calculated by Zhu Ailan et al.,(2005).  相似文献   

高精度直升机机载LiDAR在高速公路改扩建勘测中的应用可行性研究          下载免费PDF全文

郑伟安 《山东国土资源》2018,34(8)

机载LiDAR在公路勘测方面的用途日益广泛。该文对直升机机载LiDAR在高速公路改扩建中的应用技术路线可行性进行了研究论证,从地面控制测量、点云数据获取、点云数据处理、成果应用等多个方面进行了阐述,通过分析LiDAR点云数据在5种不同地面控制点布设方案校正下的点云数据精度,论证了利用地面控制点对直升机机载LiDAR点云数据进行平面和高程校正的可行性。  相似文献   

滇西北地区近年来应力场的数值模拟研究     

武永彩  李昂  唐红涛 《大地测量与地球动力学》2018,38(12):1238-1240

建立滇西北地区三维有限元地质模型，将2009~2016年GPS速度场数据作为数值模拟的位移边界条件，模拟获取该地区的构造应力场。结果表明，在楚雄至滇西北地区整体显示张性应力区；出现由“洱源鹤庆断裂-红河断裂-程海断裂”圈起的低值张性区，区域内部张性应力明显低于外部，这种张应力低值区尤其在区域四周断裂边界处，往往是地壳断裂活动的频发区；曲江断裂北端及元谋-绿汁江断裂南端出现张性应力集中区，是今后重点关注的断裂结点。  相似文献   

Review on the study of topographic effect on seismic ground motion          下载免费PDF全文

Hong Zhou 《地震科学（英文版）》2018,31(2):110-116

Topographic effect study is a very important research topic in seismology, seismic engineering,earthquake engineering, engineering earthquake construction and engineering seismology. This paper focuses on its present development status. Post-earthquake investigation has found that the existence of topography caused more serious earthquake damage. The actual seismographs also recorded the topographic amplification effect of 6 to 7 times and even more than 10 times. Numerical simulation is an important technique to study topographic effect, which complements the lack of observed records. However researches on 3-D topographic effect are not enough and need to be studied deeper. To find the main influence factors and the quantitative relationship between topography and ground motion are required very urgently. Obviously the achievements not only can be applied in the earthquake resistant design, but also can provide the quantitative pre-earthquake disaster prediction and quantitative post-earthquake disaster evaluation.  相似文献   

成武县土地利用时空变化与水系因子的关系研究          下载免费PDF全文

徐增江 《山东国土资源》2018,34(3)

成武县位于鲁西南黄河冲积平原区,水系发达,地表水资源丰富。为了分析地表水系对成武县土地利用时空变化和空间格局的影响,该文基于不同时期的遥感影像,结合实地调查和专家意见,提取区域土地利用现状图;运用DEM地表水文分析提取河流汇流累积量、水流长度、河流网络等,根据流量选取了河网。以河流为中心向两侧作缓冲区,与土地利用现状图进行空间分析,得到不同距离缓冲区内的土地利用结构。与全区域土地利用结构对比,分析不同时期在相同的缓冲区域内土地利用特征和变化,总结土地结构变化规律,结合100m,200m,300m,400m,500m,750m,1000m不同的缓冲区;通过对比各种土地利用类型在不同距离缓冲区的时空变化,从而分析水系因子对不同土地类型时空变化的影响。结果表明,不同距离缓冲区内土地利用结构不同,随着缓冲区范围的增加,耕地、建设用地、林地、园地呈现不同的变化趋势与特点,水系因子对成武县不同土地利用方式影响程度不同,水系因素对成武县土地利用空间分异有明显影响。  相似文献