Attenuation of short-period seismic waves at Mt Vesuvius, Italy     

F. Bianco  M. Castellano  E. Del Pezzo  & J. M. Ibanez 《Geophysical Journal International》1999,138(1):67-76

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Weak-contrast reflection/transmission coefficients in weakly anisotropic elastic media: P-wave incidence   总被引：1，自引：0，他引：1  

Václav Vavry&#;uk 《Geophysical Journal International》1999,138(2):553-562

We present approximate displacement and energy PP and PS reflection/transmission coefficients for weak-contrast interfaces in general weakly anisotropic elastic media. The coefficients were obtained by applying first-order perturbation theory and then expressed in a compact and relatively simple form. The formulae can be used for arbitrary orientations of the incidence plane and interface, without the need to transform the elasticity parameters to a local Cartesian coordinate system. The accuracy of the approximate formulae is illustrated for the PS reflection coefficient for two synthetic models. For these models, we also study the possibility of using the approximate PP reflection coefficient in the inverse problem.  相似文献   

Residence time of diffuse waves in the crust as a physical interpretation of coda Q: application to seismograms recorded in Mexico   总被引：4，自引：0，他引：4  

L. Margerin  M. Campillo  N. M. Shapiro  & B. van Tiggelen 《Geophysical Journal International》1999,138(2):343-352

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A reflection/transmission matrix formulation for seismoacoustic scattering by an irregular fluid–solid interface     

Taro Okamoto  & Hiroshi Takenaka 《Geophysical Journal International》1999,139(2):531-546

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太阳天顶角对太湖恰在水面下辐照度比影响的定量分析     

陶蓉茵  赵巧华  孙德勇  邱辉  钱昊钟  姜雨薇  季春华 《湖泊科学》2012,24(1):161-168

恰在水面下辐照度比变化与吸收系数、散射系数和太阳天顶角存在着密切的关系,而太阳天顶角对太湖恰在水面下辐照度比的定量影响程度尚不明确.为此,本文基于2010年5月太湖27个样点的水体光学参数和理论数值模拟,对太湖水体的情况进行研究.理论数值模拟结果表明:当太阳天顶角分别在0°～25°和70°～89°区间内变化时,对恰在水面下辐照度比增幅影响较小,增幅相差不到10%;而当太阳天顶角在30°～70°之间时,对辐照度比增幅影响很大,增幅为13.13%～52.19%.同时,利用实测数据对理论结果进行线性相关验证表明,此数值研究整体上符合太湖的实际情况.因此,对水体光学特性以及光对水生生态系统驱动作用研究的时候,应充分考虑太阳天顶角的影响.  相似文献   

瞬变电磁虚拟波场二阶Born近似成像算法     

樊亚楠  李貅  戚志鹏  鲁凯亮 《地球物理学报》2022,65(3):1144-1159

依据瞬变电磁扩散场与虚拟波动场之间的数学表达式,通过波场反变换得到虚拟波场,进而借用地震勘探上成熟的成像方法定位地质界面的位置以及形态.本文首先将时间域波动方程转换为频率域波动方程,将总波动场分为背景场和散射场、总波速分为背景速度和扰动速度,然后运用Green定理得到了散射场关于地质界面速度扰动量的表达式,并使用Bor...  相似文献   

用双矩阵法和积分方程模型估算地表的亮度温度     

张钟军  孙国清 《遥感学报》2005,9(5):531-536

提出了一种估计覆盖植被的地表亮度温度模型。模型中的植被看作是不同大小和朝向的离散散射体如叶、茎、杆构成。植被层内的体散射以及植被与地表之间的多次散射采用了双矩阵法(M atrix Doub ling)计算,地表辐射采用了积分方程模型(Integral Equation M ethod)。较高频率上的模拟结果显示植被的辐射是主要的,植被对地表辐射的衰减作用较明显。模拟的亮度温度跟SGP99机载C波段以及AMSR-E的X和Ku波段实测数据相比接近一致。  相似文献   

3D joint inversion of magnetotelluric and airborne tipper data: a case study from the Morrison porphyry Cu–Au–Mo deposit,British Columbia,Canada          下载免费PDF全文

Benjamin M. Lee  Martyn J. Unsworth  Juliane Hübert  Jeremy P. Richards  Jean M. Legault 《Geophysical Prospecting》2018,66(2):397-421

Z‐axis tipper electromagnetic and broadband magnetotelluric data were used to determine three‐dimensional electrical resistivity models of the Morrison porphyry Cu–Au–Mo deposit in British Columbia. Z‐axis tipper electromagnetic data are collected with a helicopter, thus allowing rapid surveys with uniform spatial sampling. Ground‐based magnetotelluric surveys can achieve a greater exploration depth than Z‐axis tipper electromagnetic surveys, but data collection is slower and can be limited by difficult terrain. The airborne Z‐axis tipper electromagnetic tipper data and the ground magnetotelluric tipper data show good agreement at the Morrison deposit despite differences in the data collection method, spatial sampling, and collection date. Resistivity models derived from individual inversions of the Z‐axis tipper electromagnetic tipper data and magnetotelluric impedance data contain some similar features, but the Z‐axis tipper electromagnetic model appears to lack resolution below a depth of 1 km, and the magnetotelluric model suffers from non‐uniform and relatively sparse spatial sampling. The joint Z‐axis tipper electromagnetic inversion solves these issues by combining the dense spatial sampling of the airborne Z‐axis tipper electromagnetic technique and the deeper penetration of the lower frequency magnetotelluric data. The resulting joint resistivity model correlates well with the known geology and distribution of alteration at the Morrison deposit. Higher resistivity is associated with the potassic alteration zone and volcanic country rocks, whereas areas of lower resistivity agree with known faults and sedimentary units. The pyrite halo and ≥0.3% Cu zone have the moderate resistivity that is expected of disseminated sulphides. The joint Z‐axis tipper electromagnetic inversion provides an improved resistivity model by enhancing the lateral and depth resolution of resistivity features compared with the individual Z‐axis tipper electromagnetic and magnetotelluric inversions. This case study shows that a joint Z‐axis tipper electromagnetic–magnetotelluric approach effectively images the interpreted mineralised zone at the Morrison deposit and could be beneficial in exploration for disseminated sulphides at other porphyry deposits.  相似文献   

The Earth's natural pulse electromagnetic fields for earthquake time–frequency characteristics: Insights from the EEMD–WVD method          下载免费PDF全文

Guo‐Cheng Hao  Yu‐Xiao Bai  Hui Liu  Juan Zhao  Zuo‐Xun Zeng 《Island Arc》2018,27(4)

Monitoring the Earth's natural pulse electromagnetic field (ENPEMF) signal is a geomagnetic detection approach for the Earth internal and external studies, and it provides a reference for earthquake prediction. In this paper, the Ensemble Empirical Mode Decomposition–Wigner Ville Distribution (EEMD–WVD) method is used to process the time sequences of the ENPEMF signal detected by GR‐01 receiving devices during the Lushan M_S7.0 earthquake (April 20th, 2013). By obtaining the intrinsic mode function (IMF), the time–frequency–amplitude joint distribution and the energy spectrum of the ENPEMF signal, the suspected anomalies before the earthquake could be shown. The results illustrate the ENPEMF signal before an earthquake and its time–frequency characteristics based on an EEMD–WVD algorithm, proving useful information about the anomalies around the time of the earthquake.  相似文献   

弹性各向同性介质一次散射波场高斯束Born正演          下载免费PDF全文

岳玉波  孙鹏飞  王德营  孙鹏远  郭振波  刘增强 《地球物理学报》2019,62(2):657-666

本文提出了一种弹性波一次散射波场的正演方法——弹性波高斯束Born正演.该方法以线性散射理论为基础,通过Born近似建立起地下散射点处不同波型的反射率同弹性波主分量波场之间的数据映射关系,利用高斯束所包含的走时、振幅和极性信息进行不同波型的局部平面波的合成,进而通过逆倾斜叠加将所合成的局部平面波转化为时空域的多分量地震记录.该方法不但保持了射线类方法高效的优点,还具备了处理多次走时波场的能力,从而保证了复杂构造的波场模拟的精度.文中两个数值模型的应用效果表明,本文所提出的弹性波高斯束Born正演算法具有近似于波动方程有限差分法的波场模拟精度以及高得多的计算效率.  相似文献