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Ancient terrane boundaries as probable seismic hazards: A case study from the northern boundary of the Eastern Ghats Belt, India

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Geoscience Frontiers 2014年第1期5卷 17-24页

作者： Saibal Gupta William K.Mohanty Animesh Mandal Surajit Misra department of Geology and geophysics Indian Institute of Technology KharagpurKharagpur 721302 West Bengal India

In the eastern part of the Indian shield, late Paleozoic-Mesozoic sedimentary rocks of the Talchir Basin lie precisely along a contact of Neoproterozoic age between granulites of the Eastern Ghats Mobile Belt （EGMB） and amphibolite facies rocks of the Rengali Province. At present, the northern part of the basin experiences periodic seismicity by reactivation of faults located both within the basin, and in the Rengali Province to the north. Detailed gravity data collected across the basin show that Bouguer anomalies decrease from the EGMB （~＋15 mGal）, through the basin （^-10 mGal）, into the Rengali Province （^-15 mGal）. The data are consistent with the reportedly uncompensated nature of the EGMB, and indicate that the crust below the Rengali Province has a cratonic gravity signature. The contact between the two domains with distinct sub-surface structure, inferred from gravity data, coincides with the North Orissa Boundary Fault （NOBF） that defines the northern boundary of the Talchir Basin. Post-Gondwana faults are also localized along the northern margin of the basin, and present-day seismic tremors also have epicenters close to the NOBF. This indicates that the NOBF was formed by reactivation of a Neo- proterozoic terrane boundary, and continues to be susceptible to seismic activity even at the present-day.

关键词： Eastern Ghats Mobile Belt Rengali Province Talchir Basin NOBF Bouguer anomaly Seismicity

An experimental research on the instability of ion acoustic wave with electron drift

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Chinese Science Bulletin 1996年第9期41卷 791-792页

作者：王文清 department of geophysics Peking University Beijing 100871 China

As electron temperature Te is much higher than ion temperature Ti, and electron driftspeed Vd is larger than the critical value Vdc of Vd, the ω=KVφ mode ion acoustic wave（IAW） will be instable. Under a long wave ... 详细信息

关键词： wave An experimental research on the instability of ion acoustic wave with electron drift

The Diagnostic Study on the Drought and Flood Over the Yangtze River Basin With Weather Satellite Observations

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Chinese Science Bulletin 1993年第4期38卷 308-311页

作者：蒋尚城 department of geophysics Peking University Beijing 100871 PRC

The drought and flood over the Yangtze River basin are closely related to the anomaly of the general circulation. The impacts of the disasters resulting from it on the China national economy are of great importance. Attention is paid to them by meteorologists and forecasters in China. Most of the previous studies on it used the conventional data. Because the weather satellite observation has the advantages of continuity, homogeneous spatial and temporal resolution and global coverage, it greatly makes up the defect of the conventional measurements. The outgoing longwave radiation (OLR) observed from

关键词： drought and flood over the Yangtze River basin OLR ITCZ LFO.

THE INFLUENCE OF ARCTIC AND ANTARCTIC ICE ON SOUTHERN OSCILLATION

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Acta meteorologica Sinica 1999年第4期13卷 439-449页

作者：黄嘉佑 department of geophysics Peking University Beijing 100871

The analysis of the relationship between sea ice in Arctic and Antarctic, and the Southern Oscillation Index (SOI) variation on the temporal scale of month, season and year is made in this paper. The negative correlation between sea ice in Arctic and the SOI. and the positive correlation between sea ice in Antarctic and the SOI are found. The variation of sea ice in Antarctic Pacific seems to play an important role in the influence to atmosphere. Their nonlinear relationships present more strongly than the linear relationship between them. The relationship between sea ice in Arctic and Antarctic and the SOI in the early stage is investigated. Their variation shows periodic phenomena. The maximum correlation is used to build the model for forecasting the variation of the SOI on the condition of the sea ice in Arctic and Antarctic. The explained variance of the simulated series is greater than 0.90. There exists a 17-month period in the relationship between sea ice in Arctic and Antarctic and SOI. The existing of the common factor with larger scale is discussed in this paper.

关键词： analysis of time scale nonlinear relationship simulation on statistic-dynamic model periodic model

Crustal Thickness of Funafuti Using Receiver Function Analysis

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International Journal of Geosciences 2013年第10期4卷 1333-1338页

作者： V. Srivardhan department of applied geophysics Indian School of Mines Dhanbad India

In this study, the characterization of the depth of the Mohorovicic discontinuity under the crust of Funafuti island was determined by analyzing the 3 component seismograms from 54 different earthquake events recorded by the station between 2008 and 2012. These seismograms were from teleseismic earthquakes whose epicenter lay at distances greater than 3000 km from the station. The seismograms were iteratively deconvolved in the time domain to remove the unwanted noise and then stacked to obtain better receiver functions. For analysis of the receiver functions, it was assumed that the range in which the Vp/Vs ratio would lie for the given region would be between 1.60 - 1.85 and the depth of the discontinuity was assumed to lie between 5 - 20 km. Analysis of the receiver functions showed that the Mohorovicic discontinuity was at a depth of 11 km and the Vp/Vs ratio was 1.75 for the region.

关键词： Receiver Function Analysis Funafuti Mohorovicic Discontinuity Deconvolution of Three Component Seismogram Iterative Time Domain Deconvolution

Effects of low-temperature oxidation on natural remanent magnetization of Chinese loess

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Chinese Science Bulletin 2002年第24期47卷 2100-2105页

作者： LIU Qingsong S.K.Banerjee M.J.Jackson ZHU Rixiang PAN Yongxin Institute for Rock Magnetism Department of Geology and GeophysicsUniversity of MinnesotaMinneapolisMN 55455USA Institute of Geology and geophysics Chinese Academy of SciencesBeijing 100101China

This study systematically investigates changes in both compositions and grain-sizes of magnetic minerals in the Chinese loess/paleosol samples (Yichuan, China) during thermal demagnetization processes. Between 100 and 200℃, (1) Hc and Hcr significantly decrease while Mrs and Ms remain stable; (2) concentration of the multi-domain (MD) grains increases while that of superparamagnetic (SP) grains decreases; and (3) there exists the abnormal behavior of the thermal demagnetization in the natural remanent magnetization (NRM). In addition, the corresponding changes in all these parameters are gradually muted with the increase of the pedogenesis degree. The results indicate that the observed alteration probably relates to reducing processes caused by the burning of the organic matter in samples. Before the thermal treatment, the MD grains in loess samples had been partially altered in nature by low-temperature oxidization (LTD). This CRM can be sufficiently attenuated or even removed by the reducing

关键词： chemical remanent magnetization low-temperature oxidation Verwey transition natural remanent magnetization Chinese loess.

Focal Mechanism Solutions of the 2008 Wenchuan earthquake sequence from P-wave polarities and SH/P amplitude ratios:new results and implications

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Earthquake Science 2013年第6期26卷 357-372页

作者： Yuan Tian Jieyuan Ning Chunquan Yu Chen Cai Kai Tao Institute of Theoretical and applied geophysics School of Earth and Space SciencesPeking University department of Earth Atmospheric and Planetary SciencesMIT department of Earth & Planetary Sciences Washington University

Abstract The 2008 Wenchuan earthquake, a major intraplate earthquake with Mw 7.9, occurred on the slowly deforming Longmenshan fault. To better understand the causes of this devastating earthquake, we need knowledge of the regional stress field and the underlying geodynamic processes. Here, we determine focal mechanism solutions （FMSs） of the 2008 Wenchuan earthquake sequence （WES） using both P-wave first-motion polarity data and SH/P amplitude ratio （AR） data. As P-wave polarities are more reliable information, they are given priority over SH/ PAR, the latter of which are used only when the former has loose constraint on the FMSs. We collect data from three categories：（1） permanent stations deployed by the China Earthquake Administration （CEA）; （2） the Western Sichuan Passive Seismic Array （WSPSA） deployed by Institute of Geology, CEA; （3） global stations from Incorporated Research Institutions for Seismology. Finally, 129 events with magnitude over Ms 4.0 in the 2008 WES are identified to have well-constrained FMSs. Among them, 83 are well constrained by P-wave polarities only as shown by Cai et al. （Earthq Sci 24（1）：115-125,2011）, and the rest of which are newly constrained by incorporating SH/P AR. Based on the spatial distribution and FMSs of the WES, we draw following conclusions：（1） the principle compressional directions of most FMSs of the WES are subhorizontal, generally in agreement with the conclusion given by Cai et al. （2011） but with a few modifications that the compressional directions are WNW-ESE around Wenchuan and ENE-WSW around Qingchuan, respectively. The subhorizontal compressional direction along the Longmenshan fault from SW to NE seems to have a leftlateral rotation, which agrees well with regional stress field inverted by former researchers （e.g., Xu et al., Acta Seismol Sin 30（5）, 1987; Acta Geophys Sin 32（6）, 1989; Cui et al., Seismol Geol 27（2）：234-242, 2005）; （2） the FMSs of the events not only reflected the regional stress state of th

关键词： Longmenshan fault Wenchuan earthquakesequence Focal mechanism solutions Stress

Grain Size Distribution of Soils within the Cordillera Blanca, Peru: An Indicator of Basic Mechanical Properties for Slope Stability Evaluation

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Journal of Mountain Science 2014年第3期11卷 563-577页

作者： Jan NOVOTNY Jan KLIME ARCADIS CZ a.s. Institute of Hydrogeology Engineering Geology and Applied Geophysics Charles University in Prague Albertov department of Engineering Geology Institute of Rock Structure and Mechanics Academy of Sciences of the Czech Republic v.v.i

This paper presents results of a study on the mechanical properties of sandy and gravely soils within the Cordillera Blanca, Peru. The soils were divided into groups according to their origin(glacial, fluvial, or debris flow). The grain size distribution of forty three soil samples was used to classify the soils according to the scheme of the Unified Soil Classification System(USCS). These distributions have then been used to estimate shear strength and hydraulic properties of the soils. There are clear differences between the soils which reflect their divergent origins. The glacial soils normally fit within one of two distinctive groups according to the proportion of fines(Group A, 7%-21.5%; Group B, 21%-65%). The estimation of shear strength at constant volume friction angle and peak shear strength of the glacial sediments with low content of fines was made using published data relating to the measured shear strength characteristics of soils with similar origins and grain size distributions. The estimated values were supported by measurements of the angle of repose taken from fourteen samples from two moraines and by shear tests on samples from one locality. The results of the grain size distribution werealso used to estimate the average hydraulic conductivity using the empirical Hazen formula which results were verified by field infiltration tests at two localities.

关键词： Moraines Grain size distribution Shearstrength Hydraulic conductivity Cordillera Blanca Peru

Shape and gravitational field of the ellipsoidal satellites

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Science China(Physics,Mechanics & Astronomy) 2014年第10期57卷 2015-2020页

作者： GAO BuXi HUANG Yong Institute of Geodesy and geophysics Chinese Academy of Sciences Physics department School of Science Wuhan University of Technology

The shape and gravitational field of ellipsoidal satellites are studied by using the tidal theory. For ellipsoidal satellites, the following conclusions were obtained: Firstly, in the early stage of the satellite formation, strong tidal friction allowed the satellites move in a synchronous orbit and evolve into a triaxial ellipsoidal shape. Because the tidal potential from the associated primary and the centrifugal potential from the satellite spin are nearly fixed at the surface, the early satellites are the viscoelastic celestial body, and their surfaces are nearly in the hydrostatic equilibrium state. The deformation is fixed in the surface of the satellite. By using the related parameters of primary and satellite, the tidal height and the theoretical lengths of three primary radii of the ellipsoidal satellite are calculated. Secondly, the current ellipsoidal satellites nearly maintain their ellipsoidal shape from solidification, which happened a few billion years ago. According to the satellite shape, we estimated the orbital period and spinning angular velocity, and then determined the evolution of the orbit. Lastly, assuming an ellipsoidal satellite originated in the hydrostatic equilibrium state, the surface shape could be determined by tidal, rotation, and additional potentials. However, the shape of the satellite's geoid differs from its surface shape. The relationship between these shapes is discussed and a formula for the gravitational harmonic coefficients is presented.

关键词： eliipsoidal satellites hydrostatic equilibrium secular love number shape tidal height