共查询到20条相似文献，搜索用时 262 毫秒
1.
HUANG Sixun HAN Wei & WU Rongsheng . P. O. Box Nanjing China . Key Laboratory of Meso-Scale Severe Weather /MOE Department of Atmospheric Sciences Nanjing University Nanjing China Correspondence should be addressed to Huang Sixun 《中国科学D辑(英文版)》2004,47(7):630-638
There is an international focus on the develop-ments of data assimilation systems for meteorology and physical oceanography models. Data assimilation and inverse methods are normally used for optimal control of poorly known initial boundary conditions and model parameters by taking into account both the information about dynamics of a model and the infor-mation about the true state which is constrained by a set of measurements. The research methodology of parameter estimation in meteorology ca… 相似文献
2.
《地震科学（英文版）》2010,(2)
Based on the finite element numerical algorithm,the coseismic displacements of the Wenchuan MS8.0 earthquake are calculated with the rupture slip vectors derived by Ji and Hayes as well as Nishimura and Yaji.Except in a narrow strip around the rupture zone,the coseismic displacements are consistent with those from GPS observation and InSAR interpretation.Numerical results show that rupture slip vectors and elastic properties have profound influences on the surface coseismic deformation.Results from models with different elastic parameters indicate that:①in homogeneous elastic medium,the surface displacements are weakly dependent on Poisson's ratio and independent of the elastic modulus;②in horizontally homogeneous medium with a weak zone at its middle,the thickness of the weak zone plays a significant role on calculating the surface displacements;③in horizontally and vertically heterogeneous medium,the surface displacements depend on both Poisson's ratio and elastic modulus.Calculations of coseismic deformation should take account of the spatial variation of the elastic properties.The misfit of the numerical results with that from the GPS observations in the narrow strip around the rupture zone suggests that a much more complicated rupture model of the Wenchuan earthquake needs to be established in future study. 相似文献
3.
This paper presents the calibration of Omori's aftershock occurrence rate model for Turkey and the resulting likelihoods. Aftershock occurrence rate models are used for estimating the probability of an aftershock that exceeds a specific magnitude threshold within a time interval after the mainshock. Critical decisions on the post-earthquake safety of structures directly depend on the aftershock hazard estimated using the occurrence model. It is customary to calibrate models in a region-specific manner. These models depend on rate parameters(a, b, c and p) related to the seismicity characteristics of the investigated region. In this study, the available well-recorded aftershock sequences for a set of Mw ≥ 5.9 mainshock events that were observed in Turkey until 2012 are considered to develop the aftershock occurrence model. Mean estimates of the model parameters identified for Turkey are a =-1.90, b = 1.11, c = 0.05 and p = 1.20. Based on the developed model, aftershock likelihoods are computed for a range of different time intervals and mainshock magnitudes. Also, the sensitivity of aftershock probabilities to the model parameters is investigated. Aftershock occurrence probabilities estimated using the model are expected to be useful for post-earthquake safety evaluations in Turkey. 相似文献
4.
Seismic hazard assessment based on urban active faults can provide scientific bases for city planning and projectconstruction,while numerical simulation of strong ground motion is an important method for seismic hazard pre-diction and assessment.A 3-D physical model in conformity with real strata configuration of(mainly)the Quater-nary is a prerequisite to ensure the reliability of the simulation results.In this paper,we give a detailed account ofthe technical scheme and process for creating a 3-D physical model in Kunming basin.The data used are synthe-sized from seismogeological data,borehole data,topographic data,digital elevation mode(DEM)data,seismicexploration results and wave velocity measurements.Stratigraphic division is based mainly on shear wave velocity,with strata sequence taken into consideration.The model construction is finally accomplished with ArcGIS andmany relevant programming techniques via layer-by-layer stacking(in depth direction)of the adjacent mediuminterfaces(meshes).Meanwhile,a database of 3-D physical models is set up,which provides model data and pa-rameters for strong ground motion simulation.Some processing methods and significant issues are also addressedin the paper in accordance with different types of exploration and experimental data. 相似文献
5.
《国际泥沙研究》2016,(2):139-148
Applications of sediment transport and water flow characteristics based sediment transport simulation models for a river system are presented in this study. An existing water–sediment model and a new sediment–water model are used to formulate the simulation models representing water and sediment movement in a river system. The sediment–water model parameters account for water flow characteristics embodying sediment transport properties of a section. The models are revised formulations of the multiple water inflows model describing water movement through a river system as given by the Muskingum principle. The models are applied to a river system in Mississippi River basin to estimate downstream sediment concentration, sediment discharge, and water discharge. River system and the river section parameters are estimated using a revised and the original multiple water inflows models by applying the genetic algorithm. The models estimate downstream sediment transport rates on the basis of upstream sediment/water flow rates to a system. Model performance is evaluated by using standard statistical criteria;downstream water discharge resulting from the original multiple water inflows model using the estimated river system parameters indicate that the revised models satisfactorily describe water movement through a river system. Results obtained in the study demonstrate the applicability of the sediment transport and water flow characteristics-based simulation models in predicting downstream sediment transport and water flow rates in a river system. 相似文献
6.
Great earthquakes often occur along or near active fault belts. Thus, monitoring and research on fault deformation are quite important. Methods such as short-leveling, short- baseline and integrated monitoring profile across fault belts have been used to monitor fault activities for many years. GNSS observations are mainly used to obtain the horizontal velocity field in large areas and to study the activities and deformation of major blocks. GNSS technology has been used to monitor and study the deformation of faults from a different aspects, In this paper, some applications and new explorations of GNSS are discussed. They are： （1） Research and monitoring of strike-slip activities of faults with GNSS. （2） Research and monitoring of vertical activities of faults with GNSS. （3） Investigating the laws of deformation of blocks on the sides of fault zone and setting up strain models to deduce the activities and deformation of faults with respective models and compare the deduced results with the actual measurements across fault. It is concluded that a larger discrepancy between the deduced and the observed deformation indicates a stronger interaction between the blocks, which can be important for predicting the location of a strong earthquake and assessing seismic hazard, as well as the seismicity trend. 相似文献
7.
Design of bridges against large tectonic deformation 总被引：1，自引：1，他引：0
The engineering community has devoted much effort to understanding the response of soil-structure systems to seismic ground motions, but little attention to the effects of an outcropping fault offset. The 1999 earthquakes of Turkey and Taiwan, offering a variety of case histories of structural damage due to faulting, have （re）fueled the interest on the subject. This paper presents a methodology for design of bridges against tectonic deformation. The problem is decoupled in two analysis steps： the first （at the local level） deals with the response of a single pier and its foundation to fault rupture propagating through the soil, and the superstructure is modeled in a simplified manner; and the second （at the global level） investigates detailed models of the superstructure subjected to the support （differential） displacements of Step 1. A parametric study investigates typical models of viaduct and overpass bridges, founded on piles or caissons. Fixed-head piled foundations are shown to be rather vulnerable to faulting-dnduced deformation. End-bearing piles in particular are unable to survive bedrock offsets exceeding 10 cm. Floating piles perform better, and if combined with hinged pile-to-cap connections, they could survive much larger offsets. Soil resilience is beneficial in reducing pile distress. Caisson foundations are almost invariably successful. Statically-indeterminate superstructures are quite vulnerable, while statically-determinate are insensitive （allowing differential displacements and rotations without suffering any distress）. For large-span cantilever-construction bridges, where a statically determinate system is hardly an option, inserting resilient seismic isolation bearings is advantageous as long as ample seating can prevent the deck from falling off the supports. An actual application of the developed method is presented for a major bridge, demonstrating the feasibility of design against tectonic deformation. 相似文献
8.
Numerical simulation of surface and downhole deformation induced by hydraulic fracturing 总被引：1，自引：1，他引：0
Yi-Yuan He Bao-Ping Zhang Yu-Ting Duan Cheng-Jin Xue Xin Yan Chuan He Tian-Yue Hu 《应用地球物理》2014,11(1):63-72
Tiltmeter mapping technology infers hydraulic fracture geometry by measuringfracture-induced rock deformation, which recorded by highly sensitive tiltmeters placed atthe surface and in nearby observation wells. By referencing Okada＇s linear elastic theory andGreen＇s function method, we simulate and analyze the surface and downhole deformationcaused by hydraulic fracturing using the homogeneous elastic half-space model and layeredelastic model. Simulation results suggest that there is not much difference in the surfacedeformation patterns between the two models, but there is a significant difference in thedownhole deformation patterns when hydraulic fracturing penetrates a stratum. In suchcases, it is not suitable to assume uniform elastic half-space when calculating the downholedeformation. This work may improve the accuracy and reliability of the inversion results oftiltmeter monitoring data. 相似文献
9.
Ji Shaocheng Wang ZichaoDepartment of Geology University of Montreal Montreal Quebec HC J Canada Institute of Geology China Seismological Bureau P.O. Box Beijing China 《中国地震研究》1998,(3)
Which rule of mixture is the best for predicting the overall elastic properties of polyphase rocks based on the elastic properties and volume fractions of their constituents? In order to address this question, we sintered forsterite-enstatite polycrystalline aggregates with a varied forsterite volume fraction (0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0). Elastic properties (shear, bulk, and Young's moduli) of these synthesized composites were measured as a function of pressure up to 3.0 GPa in a liquid-medium piston-cylinder apparatus using a high-precision ultrasonic interferometric technique. The experimental data can be much better described by the shear-lag model than by the commonly used simple models such as Voigt, Ruess and Hill averages, Hashin-Shtrikman bounds, Ravichandran bounds, Halpin-Tsai equations, and Paul's calculations. We attributed this to the fact that the elastic interaction and stress transfer between phases are neglected in all the models except for the shear-lag model. In particular, t 相似文献
10.
Rainfall-induced landslides have occurred frequently in Southwestern China since the Wenchuan earthquake,resulting in massive loss of people''s life and property. Fortunately,landslide early-warning is one of the most important tools for landslide hazard prevention and mitigation. However, the accumulation of historical data of the landslides induced by rainfall is limited in many remote mountain areas and the stability of the slope is easily affected by human engineering activities and environmental changes, leading to difficulties to accurately realize early warning of landslide hazards by statistical methods. The proposed warning method is divided into rainfall warning component and deformation warning component because the deformation induced by rainfall has the characteristic of hysteretic nature. Rainfall, tilted angle and crack width are chosen as monitoring indexes. Rainfall grade level that contains rainfall intensity and duration information is graded according to the variation of the safety factor calculated by 3-D finite difference numerical simulation method, and then is applied using the strength reduction method and unascertained information theory to obtain the deformation grade level of several monitored points. Finally, based on the system reliability theory, we establish a comprehensive landslide warning level method that provides four early warning levels to reflect the safety factor reductions during and post rainfall events. The application of this method at a landslide site yield generally satisfactory results and provide a new method for performing multi-index and multi-level landslide early warnings. 相似文献
11.
A. Kapička 《Studia Geophysica et Geodaetica》1992,36(2):168-176
Summary With the decreasing magnitude of the initial remanent condition of rocks, their pressure demagnetization gradually changes to pressure remanent magnetic polarization under elastic deformation. In both cases the physical cause of these changes are the irreversible changes of the domain structure of ferrimagnetic minerals. Under directional pressure the natural remanent magnetic polarization is affected namely by the generation of a relatively little stable pressure remanent magnetic polarization. With regard to paleomagnetic research, the essential thing is that secondary magnetization combined with possible elastic deformations of rocks in the Earth's crust can be eliminated relatively easily by magnetic cleaning. 相似文献
12.
A method for inversion of layered shear wavespeed azimuthal anisotropy from Rayleigh wave dispersion using the Neighborhood Algorithm 
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下载免费PDF全文 Huajian Yao 《地震科学（英文版）》2015,28(1):59-69
Seismic anisotropy provides important constraints on deformation patterns of Earth's material. Rayleigh wave dispersion data with azimuthal anisotropy can be used to invert for depth-dependent shear wavespeed azimuthal anisotropy, therefore reflecting depth-varying deformation patterns in the crust and upper mantle. In this study, we propose a two-step method that uses the Neighborhood Algorithm(NA) for the point-wise inversion of depth-dependent shear wavespeeds and azimuthal anisotropy from Rayleigh wave azimuthally anisotropic dispersion data. The first step employs the NA to estimate depthdependent VSV(or the elastic parameter L) as well as their uncertainties from the isotropic part Rayleigh wave dispersion data. In the second step, we first adopt a difference scheme to compute approximate Rayleigh-wave phase velocity sensitivity kernels to azimuthally anisotropic parameters with respect to the velocity model obtained in the first step. Then we perform the NA to estimate the azimuthally anisotropic parameters Gc/L and Gs/L at depths separately from the corresponding cosine and sine terms of the azimuthally anisotropic dispersion data. Finally, we compute the depth-dependent magnitude and fast polarization azimuth of shear wavespeed azimuthal anisotropy. The use of the global search NA and Bayesian analysis allows for more reliable estimates of depth-dependent shear wavespeeds and azimuthal anisotropy as well as their uncertainties.We illustrate the inversion method using the azimuthally anisotropic dispersion data in SE Tibet, where we find apparent changes of fast axes of shear wavespeed azimuthal anisotropy between the crust and uppermost mantle. 相似文献
13.
Prof. R. Tomaschek Ph. D. 《Pure and Applied Geophysics》1953,25(1):17-25
Summary A typical disturbance observed in the records of tilt measurements performed with horizontal pendulums in a mine at a depth of 145 m below surface, under very constant temperature conditions, has been analysed as to its correlation with the barometric pressure distribution. It is shown that the observed load tilts are not due to elastic deformations of the Earth's crust, but may be ascribed to movements of tectonic blocks of large extension. 相似文献
14.
In 1988 two large earthquakes with magnitude of Ms 7.6 and Ms 7.2 occurred in Lancang-Genma area, Southwest China. This paper discusses the determination of the spatial distribution of fault slip caused by the earthquakes using geodetic surveys. The prior information obtained from geological surveys and seismological investigations was used to determine the geometry of the fault plane and the average fault slip. The smooth constraints on the fault slips have been described by a normal distribution with hyperparameters, which are incorporated in the inversion analysis with a Bayesian model. Akaike’s Bayesian Information Criterion (ABIC) is used to get the optimal values of hyperparameters. Once the hyperparameters are determined, the maximum likelihood method is employed to estimate the patterns of a fault slip. Based on the results of inverse analysis monitoring geodetic surveys can be properly designed and conducted to obtain crust deformations and predict potential earthquake sources. 相似文献
15.
Summary A two-dimensional theory of gravitational stresses in the Earth's crust with curved boundaries is presented. The crust is modelled by an elastic plate lying on an elastic half-space. The solution obtained in the case of periodically varying boundaries is shown to be very sensitive to the ratio of both elastic parameters. Moreover, the geometrical configuration of both boundaries and their phase shift are of great importance for the resulting stress pattern. 相似文献
16.
A model is proposed that shows the relation of the block structure of the crust and earthquake sources (Sadovskii, 1979; Rodionov, 1979, 1984, 1994; Bugaev, 1999, 2011, 2014, 2015). The model can formalize how to assess the prediction of seismic regime parameters depending on the elastic limit and conditions and rate of deformation of the Earth’s crust. The spent nuclear fuel repository site in Olkiluoto (Finland) and a site in the area of the Krasnoyarsk Mining and Chemical Combine are considered as examples. It is demonstrated that the parameters of the prediction graphs limit the location of the points of magnitude repeatability graphs calculated for a site based on samples of earthquakes in the area according to different authors. This makes it possible to recommend predictive assessment of seismic regime parameters for stability monitoring of the seismic regime and safety analysis of a geological environment’s insulation properties for waste sites from the results of seismological monitoring and high-precision observations of modern movements of the Earth’s crust. 相似文献
17.
An algorithm of annealing is applied to a joint inversion of travel times and waveforms belonging to a synthetically generated seismic refraction experiment. The medium (crust and upper mantle) is modelled by a set of plane stratified layers and a halfspace. The obtained structure (elastic parameters and depth of layers) shows that, in spite of contaminating seismic noise and poor knowledge of the seismic source, annealing methods are a good tool in these kinds of inversion problems. We think that many characteristics of the annealing process described here could be used with real data and more sophisticated media for the crust and upper mantle of the earth than the present example. 相似文献
18.
2.5-D modeling and inversion techniques are much closer to reality than the simple and traditional 2-D seismic wave modeling
and inversion. The sensitivity kernels required in full waveform seismic tomographic inversion are the Fréchet derivatives
of the displacement vector with respect to the independent anisotropic model parameters of the subsurface. They give the sensitivity
of the seismograms to changes in the model parameters. This paper applies two methods, called ‘the perturbation method’ and
‘the matrix method’, to derive the sensitivity kernels for 2.5-D seismic waveform inversion. We show that the two methods
yield the same explicit expressions for the Fréchet derivatives using a constant-block model parameterization, and are available
for both the line-source (2-D) and the point-source (2.5-D) cases. The method involves two Green’s function vectors and their
gradients, as well as the derivatives of the elastic modulus tensor with respect to the independent model parameters. The
two Green’s function vectors are the responses of the displacement vector to the two directed unit vectors located at the
source and geophone positions, respectively; they can be generally obtained by numerical methods. The gradients of the Green’s
function vectors may be approximated in the same manner as the differential computations in the forward modeling. The derivatives
of the elastic modulus tensor with respect to the independent model parameters can be obtained analytically, dependent on
the class of medium anisotropy. Explicit expressions are given for two special cases—isotropic and tilted transversely isotropic
(TTI) media. Numerical examples are given for the latter case, which involves five independent elastic moduli (or Thomsen
parameters) plus one angle defining the symmetry axis. 相似文献
19.
本文以南北地震带及其附近地区大地形变监测与地震预测实践为基础,简要总结回顾了利用大地形变进行强震预测研究的工作思路、方法和一些进展;进而结合2001年昆仑山口西8．1级、2008年四川汶川8．0级特大地震前区域地壳运动变形背景和已有的研究结果,分析和探讨了基于大地形变监测,并考虑地震构造的差异性来进一步提高大震预测的科... 相似文献