GNSS多天线基线网单历元模糊度同步解算法     

汤佳明  柴艳菊  闻德保  欧吉坤 《大地测量与地球动力学》2019,39(3):262-268

提出多天线基线网单历元模糊度同步解算法，其具体实现步骤为：1）根据宽巷组合模糊度易于固定的优点，采用附加已知基线长度约束法同步解算各基线的宽巷模糊度，得到dm~cm级精度的近似基线分量；2）将解算得到的各近似基线分量作为约束，同步解算各基线的基频模糊度，以获取mm级精度的基线矢量。该方法的关键在于检验各历元宽巷模糊度解算的正确性，以获取可靠的近似基线分量，为解算各基线的基频模糊度提供准确的基线先验信息。由于动态情况下各历元观测信息比较少，单纯依赖ratio检验不可靠，提出结合基线误差、单位权中误差、基线网模糊度闭合环及ratio值等对多组宽巷模糊度进行检验，避免ratio值设置不当导致模糊度检验中发生纳伪和弃真问题。实测数据结果证明，该处理方法使得模糊度解算的成功率提高1%~2%，可以获取移动平台更丰富的导航信息，提高其服务能力。  相似文献   

Seismic amplitude inversion for the transversely isotropic media with vertical axis of symmetry     

Feng Zhang  Tuo Zhang  Xiang-Yang Li 《Geophysical Prospecting》2019,67(9):2368-2385

Transverse isotropy with a vertical axis of symmetry is a common form of anisotropy in sedimentary basins, and it has a significant influence on the seismic amplitude variation with offset. Although exact solutions and approximations of the PP-wave reflection coefficient for the transversely isotropic media with vertical axis of symmetry have been explicitly studied, it is difficult to apply these equations to amplitude inversion, because more than three parameters need to be estimated, and such an inverse problem is highly ill-posed. In this paper, we propose a seismic amplitude inversion method for the transversely isotropic media with a vertical axis of symmetry based on a modified approximation of the reflection coefficient. This new approximation consists of only three model parameters: attribute A, the impedance (vertical phase velocity multiplied by bulk density); attribute B, shear modulus proportional to an anellipticity parameter (Thomsen's parameter ε−δ); and attribute C, the approximate horizontal P-wave phase velocity, which can be well estimated by using a Bayesian-framework-based inversion method. Using numerical tests we show that the derived approximation has similar accuracy to the existing linear approximation and much higher accuracy than isotropic approximations, especially at large angles of incidence and for strong anisotropy. The new inversion method is validated by using both synthetic data and field seismic data. We show that the inverted attributes are robust for shale-gas reservoir characterization: the shale formation can be discriminated from surrounding formations by using the crossplot of the attributes A and C, and then the gas-bearing shale can be identified through the combination of the attributes A and B. We then propose a rock-physics-based method and a stepwise-inversion-based method to estimate the P-wave anisotropy parameter (Thomsen's parameter ε). The latter is more suitable when subsurface media are strongly heterogeneous. The stepwise inversion produces a stable and accurate Thomsen's parameter ε, which is proved by using both synthetic and field data.  相似文献   

Precise Determination of Astronomical Azimuth by the Hour Angle Method of Multiple Meridian Stars     

《Chinese Astronomy and Astrophysics》2020,44(4):536-548

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联合BDS/GPS的北斗广域差分实时电离层延迟格网改正方法研究     

房成贺  陈俊平  兰孝奇  张磊 《大地测量与地球动力学》2019,39(2):169-177

研究并实现中国区域北斗广域差分实时电离层延迟格网改正算法，针对北斗单系统实时建立电离层延迟格网的不足，提出联合BDS/GPS的北斗广域差分实时电离层延迟改正方法。比较BDS、GPS以及BDS/GPS观测的实时电离层延迟格网，并利用北斗单频单点伪距定位进行精度验证。结果表明，在有效格网点覆盖充足的地区，BDS与GPS实时电离层延迟格网定位效果相当；而联合BDS/GPS观测的实时电离层延迟格网极大提高了偏远地区的单频定位精度与可定位历元数，也使原本单系统格网覆盖充足的地区定位效果得到进一步增强和稳定。  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   

Approximate traveltime inversion in downhole microseismic monitoring     

Sergey Yaskevich  Anton A. Duchkov  Yuriy Ivanov 《Geophysical Prospecting》2020,68(3):918-925

In downhole microseismic monitoring, accurate event location relies on the accuracy of the velocity model. The model can be estimated along with event locations. Anisotropic models are important to get accurate event locations. Taking anisotropy into account makes it possible to use additional data – two S-wave arrivals generated due to shear-wave splitting. However, anisotropic ray tracing requires iterative procedures for computing group velocities, which may become unstable around caustics. As a result, anisotropic kinematic inversion may become time consuming. In this paper, we explore the idea of using simplified ray tracing to locate events and estimate medium parameters. In the simplified ray-tracing algorithm, the group velocity is assumed to be equal to phase velocity in both magnitude and direction. This assumption makes the ray-tracing algorithm five times faster compared to ray tracing based on exact equations. We present a set of tests showing that given perforation-shot data, one can use inversion based on simplified ray-tracing even for moderate-to-strong anisotropic models. When there are no perforation shots, event-location errors may become too large for moderately anisotropic media.  相似文献   

面向目标自适应有限元法的带地形三维大地电磁各向异性正演模拟          下载免费PDF全文

曹晓月  殷长春  张博  黄鑫  刘云鹤  蔡晶 《地球物理学报》2018,61(6):2618-2628

传统三维大地电磁各向异性模拟均是基于规则六面体网格，计算精度有限且较难拟合复杂地质条件.本文采用面向目标自适应非结构矢量有限元法，对三维大地电磁各向异性介质进行模拟.首先从电场双旋度方程出发，利用伽辽金方法建立变分方程；然后利用电流密度连续性条件构建适合大地电磁各向异性问题的加权后验误差估计方法，实现面向目标的网格自适应正演；最后通过典型算例分析各向异性对网格自适应和大地电磁响应的影响特征以及各向异性的识别方法.本文算法能够高精度地拟合起伏地表和任意各向异性介质，适用于分析复杂地电条件大地电磁响应特征，为提高大地电磁资料解释水平提供了理论基础.  相似文献   

利用背景噪声成像研究合肥-金华剖面地壳速度结构及径向各向异性的东西差异   总被引：3，自引：1，他引：2       下载免费PDF全文

吴珊珊  姜明明  何玉梅  赵亮  艾印双 《地球物理学报》2018,61(2):584-592

背景噪声成像能够为地壳内部结构提供地震波速的观测证据，能够增进对地壳结构与物性的认识.本文利用背景噪声成像方法对合肥-金华流动地震台阵55个台站数据进行了分析反演，获得了华北克拉通与华南块体东部构造边界附近区域的地壳S波速度与径向各向异性结构.成像结果表明，以东经118°-118.5°附近为界，西北部表现为地壳低速异常和中下地壳正的径向各向异性，东南部表现为地壳高速异常，下部地壳存在负的径向各向异性.由此，本文推测地震波速结构差异反映了地壳内部物质与温度的差异，这种差异与两个地区自中生代晚期以来经历了截然不同的岩浆活动相关.  相似文献   

川滇地区壳幔地震各向异性研究进展     

张艺  高原  赵镇岭 《中国地震》2018,34(2):207-218

根据川滇地区已有的地震各向异性研究结果,利用体波、面波资料的结果,分析川滇地区不同构造尺度、不同深度的地震各向异性特征。对比不同方法研究川滇地区介质各向异性的特点,探讨了该地区的介质连续性及壳幔耦合状态。分析认为,地壳上地幔各向异性的差异表明,川滇地区具有复杂的地壳及上地幔形变机制。因此,对于川滇地区壳幔地震各向异性的深入理解,需在理论上和高密度数据资料基础上加强量化分析和综合研究。  相似文献   

江苏地区渗流方位角变化特征分析     

鲍海英  李飞  蒋延龄  卜玉菲  韩丽 《地震地磁观测与研究》2018,39(6):114-119

利用谐波振幅和峰谷值2种方法，计算江苏地电台站渗流方位角，并尝试利用渗流方位角进行映震分析，结果表明：①使用2种方法计算的渗流方位角相差不大，由此所得地震对应关系应基本可靠；②高邮地电台渗流方位角与高邮-宝应M_S 4.9地震对应关系较好。因此，对江苏地区开展渗流方位角变化特征分析具有一定意义。  相似文献