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1.
《Journal of Applied Geophysics》2010,72(4):149-156
Characterization of shallow structures was performed by using different approaches analysing both P- and S-wave seismic data with different resolution. The refraction tomography provided P and S velocity models of the first 80 m, while the reflection seismic processing gives a reasonable stacking velocity field until 300 m depth for both P- and S-wave data. So, we estimated the Vp/Vs ratio and an empirical relationship between the two velocities. We characterised the shallow layers using tomographic velocity models and the deeper layers using seismic images with different resolution. The seismic images were obtained by conventional CMP reflection seismic processing and by a novel multi-refractor imaging technique. 相似文献
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To develop P management guidelines for poultry litter application in Oxisols of Brazil, the relationship between water soluble P (WSP), soil test P (STP), and degree of P saturation (DPS) needs to be established. The study examined this relationship in Oxisols of Brazil receiving poultry litter. Soils were analyzed for Mehlich‐1 P (M1‐P), WSP, P fractions, P sorption index (PSI), and P saturation based on Mehlich‐1 extractable P, Al, Fe (DPSM1), and PSI (DPSPSI). Surface water bodies in the catchment area were examined for inorganic and total P. All the surface water bodies in the catchment area of the sampled plots were highly enriched in inorganic and organic P. Enrichment of soil P fractions following poultry litter application followed the order HCl‐bound > NaOH‐bound > NaHCO3‐bound fraction. M1‐P was correlated to labile (NaHCO3‐Pi), and stable P pools (NaOH‐P and HCl‐P) and reflected the cumulative P accumulation in these soils. P saturation indices increased with cumulative P addition and increasing M1‐P. WSP increased with increasing DPS and a change point was noticed at 23% DPSPSI (equivalent to DPSM1 of 16.5%) corresponding to M1‐P of 44.5 mg P kg?1, which could be regarded as threshold for P loss in these soils. 相似文献
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An analysis of P travel-times from the Nevada Test Site is carried out using data from 23 explosions between 1966 and 1976. Results show a scatter of travel times which may partly arise in the lower mantle. P travel-times over the distance range 25–100° are 2.0–2.5 s faster than the Jeffreys-Bullen travel times. 相似文献
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Daihua Ye Tingxuan Li Xia Huang Xizhou Zhang Zicheng Zheng Haiying Yu 《洁净——土壤、空气、水》2015,43(2):279-286
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S.D. Kogan 《Physics of the Earth and Planetary Interiors》1984,34(3):150-158
This paper deals with the construction procedure for regional travel-time curves and the new average global curve for P times. This paper also presents new average global values for PcP times constructed from observed travel times. 相似文献
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Earthquake focal mechanisms and stress field in Sichuan-Yunnan area determined using P wave polarity and short period P and S waveform data 总被引：2，自引：0，他引：2
Based on waveform data, several methods to determine focal mechanisms of small earthquakes were developed since 1980. Kisslinger (1980) and Julian, Foulger (1996) proposed an approach to determine solution by using amplitude ratio of P and S wave. Schwartz (1995) devised a method to determine solutions by the use of polarity data and amplitudes of seismogram envelopes. Amplitudes of short period seismic waves propagating in an inhomogeneous medium are sensitive to the variation in velocity a… 相似文献
7.
Lianqing Zhou Cuiping Zhao Zhangli Chen Sihua Zheng 《Pure and Applied Geophysics》2012,169(1-2):123-139
High-resolution three-dimensional V P and V P /V S images in the Longtan reservoir area were obtained from local earthquake data by using 3,178 events with total 24,153 P-wave and 23,987 S-wave arrivals collected from 23 seismic stations. The tomographic images show that significant V P heterogeneities can be seen at layers of different depth in the Longtan reservoir area. Low-V P anomalies both beneath and around the main rivers in the reservoir area may be related to the composition of rocks which are mainly deposit carbonate and arenaceous shale, which contributes to water saturation. We deduced that the high porosity rocks beneath the main rivers may be fully saturated with water. The phenomenon that V P is relatively high in the area which is 10–20?km away from the rivers indicates that horizontal saturation of water is limited within a small range of area that is about 10–20?km from the main rivers. The characteristic is significant that seismicity in the Longtan reservoir area is coincident with the distribution of the low-V P area. V P /V S tomographic images show that V P /V S ranges from 1.8 to 2.05 in shallow layers above 4?km depth beneath the Longtan reservoir, suggesting the properties of the rocks are limestone and shale. At the depth of 7?km, the distribution of V P /V S image varies quite remarkably, especially in the dam area. This demonstrates that the range of influence by the saturation of water in the media below the reservoir surface can reach 4–7?km depth in the dam area. 相似文献
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Abou-Bakr K. Ibrahim 《Pure and Applied Geophysics》1971,91(1):114-133
Summary Using the Haskell matrix formulation, theoretical reflection coefficient curves have been calculated for a multi-layered core-mantle boundary for comparison with observational data. Two cases are considered, first when the shear velocity in the core is equal to zero and second when the core has a finite rigidity. If the velocity contrast is large between the imbedded layer and the mantle, the reflection coefficient curves for the multi-layered medium are irregular in shape as compared to those for two half-spaces, representing the core and the mantle, respectively. The reflection coefficient curves show an oscillatory character if the imbedded layer is thick and has a high velocity contrast.The observational data consist of short-period vertical-component seismograph records ofP andPcP from nuclear explosions in the Aleutian chain, Nevada, Novaya Zemlya, Kazakh and Sahara. Attenuation and geometrical spreading are taken into consideration. Four different models for the quality factorQ are applied to the observational data. The data are found to be much affected by theQ-model used for the corrections.Based on proposedQ-values, a model for the core-mantle boundary is found, characterized by two low-velocity layers at the bottom of the mantle. The thicknesses are 16.10 km (outer layer) and 19.96 km (inner layer), the compressional wave velocities 12.17 km/sec and 10.94 km/sec and the shear wave velocities are 6.29 km/sec and 5.33 km/sec, respectively. A better fit to this model is found when in addition the shear velocity in the outer core is 2.20 km/sec and the density ratio at the core-mantle boundary is 1.07. In other words, the observations favour a layer of finite rigidity in the outer core rather than a fluid one. 相似文献
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《应用地球物理》2006,3(3):163-168
In multi-component seismic exploration, the horizontal and vertical components both contain P- and SV-waves. The P- and SV-wavefields in a seismic record can be separated by their horizontal and vertical displacements when upgoing P- and SV-waves arrive at the sea floor. If the sea floor P wave velocity, S wave velocity, and density are known, the separation can be achieved in ther-p domain. The separated wavefields are then transformed to the time domain. A method of separating P- and SV-wavefields is presented in this paper and used to effectively separate P- and SV-wavefields in synthetic and real data. The application to real data shows that this method is feasible and effective. It also can be used for free surface data. 相似文献
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利用中国东南部地震台站的波形数据,通过远震P波层析成像方法反演了福建及台湾地区的上地幔P波速度结构,据此分析了华夏块体的构造属性并探讨了中国东南部上地幔的深部动力学机制.结果表明,研究区上地幔速度结构存在明显的横向非均匀性,它们与区域构造的深部动力学成因密切相关.宏观上,NE向展布的低速异常与东南沿海地区中新生代火成岩的条带状分布保持了较好的一致性,推测其上地幔可能存在幔源物质上涌;以政和—大埔断裂带为界,东、西华夏块体的速度结构存在差异,结合前人的研究结果分析,东、西华夏块体岩石圈减薄和中新生代岩浆活动的驱动机制有所不同,西华夏块体为“板块俯冲+岩浆底侵(岩石圈拆沉)”的动力学模式,东华夏块体是“玄武质岩浆迁移+岩浆底侵”的动力学模式. 相似文献
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William D. Taylor 《Aquatic Sciences - Research Across Boundaries》2010,72(1):13-20
Techniques recently developed for measuring P regeneration, particulate P turnover, and PO4
3− concentration in lakewater assume that dissolved 32P (D32P) released by plankton is PO4
3−. To test this assumption, I obtained samples of D32P regenerated from whole plankton communities by labeling the communities with 32P-PO4
3− then blocking re-uptake and transformation of regenerated D32P with two competitive inhibitors, unlabeled 31P-PO4
3− and pyrophosphate. Under these conditions, regenerated D32P accumulated and could be examined by gel chromatography to discern how much of it was 32P-PO4
3− versus higher molecular weight P compounds. I estimated that most or all of the D32P released was 32P-PO4
3−. I also observed that the amount of DP observed on filtration of lakewater depended on the method employed to obtain the
filtrate. Therefore, I also separated particulate 32P from D32P with dialysis membrane (100,000 MW cutoff) without pressure. There was little DP larger than PO4
3− and no DP >5,000 MW in the dialysate, leading me to conclude that DP <100,000 MW was a minor component of both regenerated
and total P. I suggest that under P-limited conditions that most dissolved P observed in lakewater filtrates may be intact
viruses and cell constituents liberated in the filtration process. These results are mostly congruent with Lean’s (J Fish
Res Board Can 30:1525–1536, 1973) model of P-cycling in lake plankton, although the nature of “colloidal P” in Lean’s model should be further investigated. 相似文献
13.
本文提出一种角度部分叠加资料同时反演纵波速度和泊松比的方法.以角度部分叠加资料为基础,利用地震波振幅随入射角变化与弹性参数间的数学关系,基于非线性最优化理论,通过将最小平方问题转化为大型带状矩阵的求解问题,采用测井约束逐道外推技术依次求得该角度剖面每个点的纵波和泊松比值.通过由每个角度叠加剖面反演得到的相应角度范围的纵波速度和泊松比剖面的对比分析,进一步得到地震波垂直入射时的纵波速度和泊松比,为地震资料的岩性及含气性解释提供丰富的参数信息. 相似文献
14.
Introduction Attenuation parameter Q~(-1) is an important factor for understanding the physical mechanism of seismic wave attenuation in relation to the composition and physical condition of the Earth′s interior (Sato, 1992) and it is also an indispensable parameter for the quantitative prediction of strong ground motion from the viewpoint of engineering seismology. Hence numerous studies of Q~(-1) have been carried out worldwide by using different methods and concentrate on seismically acti… 相似文献
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本文以分层均匀"多层介质模型"为依据,正演模拟多炮人工地面地震记录.其观测方式为:三炮位置分别在1500m,2500m,3500m处;道检距25m,140道(或道检距5m,700道),偏移距1000 m.为提高地震反射层析成像的精度,运用"走时最小纵横波速度层析成像"与"波形基本解纵横波速度层析成像"相结合的方法,反演... 相似文献
16.
J.H. Ansell 《Physics of the Earth and Planetary Interiors》1981,26(4):246-249
A scalar potential representation for a P wave in an inhomogeneous medium is developed from ray theory and is shown to be generally applicable to both P and S waves. It is shown that the P to S coupling takes place at one order of frequency down from the principal components and that the principal components depend on the density only at the source and observer positions. 相似文献
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