小波阈值法在JCZ系列超宽频带地震仪记录的地震数据中的应用及探讨     

王海斌  周云耀  吕永清  向涯 《大地测量与地球动力学》2021,41(3):323-330

为了对JCZ系列超宽频带地震仪采集到的地震数据进行有效去噪,探讨小波阈值法在不同地震数据中去噪的实际效果。首先介绍小波法的基本理论与去噪标准,探讨不同小波基的选取、不同分解、重建尺度与阈值的选取及处理方式对小波阈值法最终去噪效果产生的影响;使用控制变量法,选取武汉水院地震台的记录数据,探讨如何获得较好的去噪效果。为了比较小震和中强震两种情况下相同方法的处理效果,将选择好的小波基与几何尺度用于震例数据去噪发现,在实际地震去噪处理中基于样本数估计选取的阈值具有一定局限性,且相同阈值在不同震级的震例数据中具有不同的去噪结果。最后使用小波阈值对JCZ系列超宽频带地震仪采集到的地震数据进行去噪发现,小波阈值去噪对于P波初动的识别判断也具有一定意义。  相似文献   

Lithogeochemical features of Riphean fine-grained terrigenous rocks in the Kama-Belaya aulacogen and their formation conditions     

A. V. Maslov  M. V. Isherskaya  M. T. Krupenin  V. G. Petrishcheva  T. Ya. Gulyaeva  N. P. Gorbunova 《Lithology and Mineral Resources》2010,45(2):172-200

Lithogeochemical features of Riphean fine-grained terrigenous rocks of the Kama-Belaya aulacogen are discussed. It is shown that aluminosiliciclastic material delivered to the aulacogen during the Riphean was characterized by a low maturity degree. The successively increasing K₂O/Al₂O₃ values in the Riphean summary section correlate negatively with the CIA index values, indicating a gradually strengthening tendency for climate aridization in erosion zones. Data on some indicator ratios of trace elements and REE systematics in Riphean silty mudstones and shales of the Kama-Belaya aulacogen imply the involvement of mafic and ultramafic rocks, in addition to acid igneous and metamorphic varieties, in erosion during accumulation of the Nadezhdino, Tukaevo, Ol’khovka, Usinsk, and Priyutovo formations. Comparison of data on the composition of rocks in provenances based on the mineralogical-petrographic study of sandstones and investigation of geochemical features of silty mudstones and shales revealed their sufficiently high similarity. The geochemical data made it possible to specify the composition of rocks in provenances. Low Ce/Cr values in the fine-grained terrigenous rocks of the Lower Riphean Kyrpy Group suggest their formation with a significant contribution of erosion products of the Archean substrate, which is atypical for higher levels of the section. Thus, the Early-Middle Riphean transition period was likely marked by substantial changes in the mineral composition of material delivered to the Kama-Belaya aulacogen. The lack of exhalative components in the examined specimens of silty mudstones and shales points to a relatively low permeability of the Earth’s crust in the eastern East European Platform through the entire Riphean.  相似文献   

月球重力场研究及其应用进展     

徐亚  郝天珧 《地球化学》2010,39(1):25-31

月球重力场研究及相关应用是月球科学探测中的重要内容之一。本文回顾了月球重力测量及月球重力场模型、月球地形模型等主要研究进展,总结了月球重力场（包括地形）在月球内部结构研究,特别是在月壳结构以及月球质量瘤等方面取得的研究成果。此外,月球重力场还应用于月幔／月核研究、月球均衡状态、月球物质成分及月球演化历史的研究中。随着我国嫦娥探月计划的实施,利用其探测数据建立自主重力场模型及地形模型成为我国探月研究的基础工作之一。在此基础上可开展月壳结构、月球均衡状态、月球质量瘤及月壳成分等研究,同时借鉴地球科学中相关学术思想和方法技术,从而促进对月球及类地行星等结构的研究。  相似文献   

Charnockitization and enderbitization of mafic granulites in the Porya Bay area,Lapland Granulite Belt,Southern Kola Peninsula: I. Petrology and geothermobarometry     

S. P. Korikovsky  L. Ya. Aranovich 《Petrology》2010,18(4):320-349

Charnockitization of mafic Opx-Cpx-Grt-Hbl-Bt-Pl ± Qtz granulites and Hbl-Opx-Bt hornblendites was studied in the southeastern part of the Lapland Granulite Belt. The evolutionary trends of the whole-rock compositions and mineral assemblages indicate that the rocks were affected by Na-K-Si-H₂O-CO₂-Cl brines, which came from outside, alkalinized and debasified the granulites, introduced Na, K, and Si into them, and depleted them in Mg, Fe, and Ca prior to the onset of charnockite melting; the latter began in the granulites only in their most extensively debasified domains. In the course of alkaline metasomatism, pyroxene were replaced by secondary hornblende and biotite with high Ti concentrations, analogous to those in the unaltered granulites. This suggests that the pre-charnockite amphibolization and biotitization were induced not by a temperature decrease but by the effect of Na- and K-bearing fluid during the metamorphic culmination. The metasomatically altered granulites, which were transformed into leucocratic disintegrated amphibolite skialiths, were gradually resorbed and dissolved in the charnockite melt, whose bulk composition corresponded to low-alkaline granites and tonalites. Hence, no contamination took place, and the excess Mg, Fe, and Ca amounts with respect to the eutectic composition were removed from the reaction zone. Variation diagrams indicate that the whole-rock composition of the granulites is gradually shifted toward the composition of charnockitoids. In certain instances, however, melanocratic Hbl-Grt-Opx-Cpx-Pl rims were formed along the granulite-charnockite interface, with the bulk composition of these fringes richer in Mg, Fe, and Ca than that of the ambient granulites. The reason for this was the sporadic redeposition of Mg, Fe, and Ca, which were mobilized from during charnbockitization and redeposited immediately in the reaction zone. In addition, rocks around the charnockite veins bear autonomous melanocratic Grt-Opx-Cpx-Hbl ± Mag ± Ilm ± Scp ± Pl ± Qtz veins whose mineral assemblages and bulk composition are close to those of the melanocratic rims around charnockitoids. The veins were formed via the transportation of Mg, Fe, and Ca for long distances outside the charnockitization zones. TWQ thermobarometric calculations indicate that the pre-charnockite alkaline metasomatism and debasification (amphibolization, biotitization, and feldspathization), anatectic formation of charnockite migma or magma, and the development of the melanocratic veins took place at the peak of the high-pressure granulite metamorphism at the same P-T parameters: approximately 800°C and 9–9.5 kbar. The calculated composition of the charnockitizing fluids suggests that they were homogeneous brines with $ X_{H_2 O} = 0.45 $ X_{H_2 O} = 0.45 , $ X_{CO_2 } = 0.10 $ X_{CO_2 } = 0.10 , X _NaCl = 0.30, and X _KCl = 0.15.  相似文献   

Isotopic (Sr,Nd, O) systematics of the high Sr-Ba Late Miocene granitoid intrusions from the Caucasian Mineral Waters region     

E. O. Dubinina  A. A. Nosova  A. S. Avdeenko  L. Ya. Aranovich 《Petrology》2010,18(3):211-238

This paper is dedicated to the interpretation of isotope-geochemical data on high Sr-Ba granitoids exemplified by their typical representatives—Late Miocene laccoliths of the Caucasian Mineral Waters (CMW). These massifs are made up of amphibole granites, granosyenites, syenites, and leucogranites, which show particular behavior of Sr, Nd, and O isotope systems. The syenites and granosyenites are characterized by δ¹⁸O variations from 8 to 10‰. As compared to them, the amphibole granites have lowered (up to 7‰), while leucogranites, elevated (up to 12.5–13.7‰) oxygen isotope compositions. The (⁸⁷Sr/⁸⁶Sr)_8.3 ratio in the granitoids accounts for 0.7083–0.7086, whereas σ_Nd(T) varies from −4.2 to −2.1.  相似文献   

Oxygen isotopic composition of coexisting minerals of sillimanite-hypersthene rocks from the Por’ya bay area: Evidence of fluid involvement in granulite-facies metamorphism   总被引：1，自引：0，他引：1  

L. Ya. Aranovich  E. O. Dubinina  A. S. Avdeenko  Yu. M. Lebedeva  S. A. Bushmin  D. D. Dolivo-Dobrovol’skii 《Geochemistry International》2010,48(8):739-751

Hypersthene-garnet-sillimanite-quartz enclaves were studied in orthopyroxene-plagioclase and orthopyroxene-clinopyroxene crystalline schists and gneisses from shear zones exposed in Palenyi Island in the Early Proterozoic Belomorian Mobile Belt. Qualitative analysis of mineral assemblages indicates that these rocks were metamorphosed to the granulite facies (approximately 900°C and 10–11 kbar). Oxygen isotopic composition was determined in rock-forming minerals composing zones of the enclaves of various mineralogical and chemical composition. The closure temperatures of the isotopic systems obtained by methods of oxygen isotopic thermometry are close to the values obtained with mineralogical geothermometers (Grt-Opx and Grt-Bt) and correspond to the high-temperature granulite facies (860–900°C). Identified systematic variations in the δ¹⁸O values were determined in the same minerals from zones of different mineral composition. Inasmuch as these zones are practically in contact with one another, these variations in δ¹⁸O cannot be explained by the primary isotopic heterogeneity of the protolith. The model calculations of the extent and trend of the δ¹⁸O variations in minerals suggest that the only mechanism able to generate the zoning was fluid-rock interaction at various integral fluid/rock ratios in discrete zones. This demonstrates that a focused fluid flux could occur in lower crustal shear zones. The preservation of high-temperature isotopic equilibria of minerals testifies that the episode of fluid activity at the peak of metamorphism was very brief.  相似文献   

Thermal expansion behavior of Ce2Zr2O7 up to 898 K in conjunction with structural analyses by neutron diffraction     

Philippe E. Raison  Claudiu C. Pavel  Regis Jardin  Emmanuelle Suard  Richard G. Haire  Karin Popa 《Physics and Chemistry of Minerals》2010,37(8):555-559

The thermal expansion of cubic pyrochlore Ce₂Zr₂O₇ has been measured from room temperature to 898 K on polycrystalline material in conjunction with structural analyses using neutron diffraction. This compound has a thermal expansion coefficient in line with the other comparable lanthanoide pyrochlore oxides. The coefficient can be expressed as α(T) = 8.418 × 10⁻⁶ + 0.9861 × 10⁻⁹ × T. The structural refinements performed for each measured temperature showed a comparable linear evolution of the Ce–O/Zr–O distances (within 0.57%).  相似文献   

Wave propagation in an inhomogeneous cross‐anisotropic medium     

Cheng‐Der Wang  Ya‐Ting Lin  Yu‐Shiuh Jeng  Zheng‐Wei Ruan 《国际地质力学数值与分析法杂志》2010,34(7):711-732

Analytical solutions for wave velocities and wave vectors are yielded for a continuously inhomogeneous cross‐anisotropic medium, in which Young's moduli (E, E′) and shear modulus (G′) varied exponentially as depth increased. However, for the rest moduli in cross‐anisotropic materials, ν and ν′ remained constant regardless of depth. We assume that cross‐anisotropy planes are parallel to the horizontal surface. The generalized Hooke's law, strain–displacement relationships, and equilibrium equations are integrated to constitute governing equations. In these equations, displacement components are fundamental variables and, hence, the solutions of three quasi‐wave velocities, V_P, V_SV, and V_SH, and the wave vectors, $\mathop{\mathop{l}\limits^{\rightharpoonup}}\nolimits_{P}$ $\mathop{\mathop{l}\limits^{\rightharpoonup}}\nolimits_{\mathit{SV}}$, and $\mathop{\mathop{l}\limits^{\rightharpoonup}}\nolimits_{{\mathit{SH}}}$, can be generated for the inhomogeneous cross‐anisotropic media. The proposed solutions and those obtained by Daley and Hron, and Levin correlate well with each other when the inhomogeneity parameter, k, is 0. Additionally, parametric study results indicate that the magnitudes and directions of wave velocity are markedly affected by (1) the inhomogeneous parameter, k; (2) the type and degree of geomaterial anisotropy (E/E′, G′/E′, and ν/ν′); and (3) the phase angle, θ. Consequently, one must consider the influence of inhomogeneous characteristic when investigating the behaviors of wave propagation in a cross‐anisotropic medium. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Role of solar activity in formation of the anomalous El Nin’o current     

V. Ya. Vovk  L. V. Egorova 《Geomagnetism and Aeronomy》2007,47(1):94-100

Monthly indices of Southern Atmospheric Oscillation (SOI) and corresponding Wolf numbers, geoeffective solar flares, magnetic AE indices as well as daily average values of the southward component of the interplanetary magnetic field (IMF B _z) and data on the wind characteristics at Antarctic stations Vostok, Leningradskaya, and Russkaya are analyzed. It is shown that a sharp decrease in the SOI indices, which corresponds to the beginning of El Nin’o (ENSO), is preceded one or two months before by a 20% increase in the monthly average Wolf numbers. In warm years of Southern Atmospheric Oscillation a linear relationship is observed between the SOI indices and the number of geoeffective solar flares with correlation coefficients p < ?0.5. It is shown that in warm years a change in the general direction of the surface wind to anomalous at the above stations is preceded one or two days before by an increase in the daily average values of IMF B _z. An increase in the SOI indices is preceded one or two months before by a considerable increase in the monthly average values of the magnetic AE indices.  相似文献   

Diurnal periodicity of earthquakes in central Asia: Part 5. Catalogue of the Kyrgyz digital broadband seismic network KNET     

A. Ya. Sidorin 《Seismic Instruments》2007,43(1):43-55

Detailed analysis of the information contained in the earthquake catalogue of the Kyrgyz digital broadband seismic network over the period from 1994 to 2005 is performed. The graphs of earthquake recurrence were plotted and analyzed. The energy threshold of representativeness of the catalogue was determined. Stroboscopic and Fourier spectra of time series of earthquakes in the range of periods T ≤ 48 h are presented. A similarity between the obtained graph of diurnal course of seismicity with similar graphs for other regions was found. Peculiarities of diurnal course of earthquakes of different energy were studied. Earthquake sampling of the southwestern part of the territory presented in the catalogue was studied separately. Erroneous information in the catalogue caused by explosions is identified. A conclusion is made about a need for special measures to identify the explosions contained in the catalogue. Special algorithms for processing digital seismograms should be used in addition to collecting information about the time of explosions.  相似文献