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1.
IntroductionSignificant progress has been made in the application of crustal deformation data to the intermediate and long-term earthquake prediction, seismicity situation judgment and the intermediate-term prediction, but the application to the intermediate and short-term earthquake prediction and research is difficult. This is because the crustal deformation data are not stable and contain strong intermediate and long-term deformational and disturbing signals, annual deformation signals and … 相似文献
2.
The response-spectrum mode superposition method is widely used for seismic response analyses of linear systems. In using this method, the complete quadratic combination （CQC） is adopted for classically damped linear systems and the complex complete quadratic combination （CCQC） formula is adopted for non-classically damped linear systems. However, in both cases, the calculation of seismic response analyses is very time consuming. In this paper, the variation of the modal correlation coefficients of displacement, velocity and displacement-velocity with frequency and damping ratios of two modes of interest are studied, Moreover, the calculation errors generated by using CQC and square-root-of-the-sum-of-thesquares （SRSS） methods （or CCQC and CSRSS methods） for different damping combinations are compared. In these analyses, some boundary lines for classically and non-classically damped systems are plotted to distinguish the allowed minimum frequency ratio at given geometric mean of the damping ratios of both modes if their relativity is neglected. Furthermore, the simplified method, which is a special mode quadratic combination method considering only relativity of adjacent modes in CQC method and named simplified CQC or partial quadratic combination （PQC） method for classically damped linear system, is proposed to improve computational efficiency, and the criterion for determination of how many correlated modes should be adopted is proposed. Similarly, the simplified CCQC or complex partial quadratic combination （CPQC） method for the non-classically damped linear system and the corresponding criterion are also deduced. Finally, a numerical example is given to illustrate the applicability, computational accuracy and efficiency of the PQC and CPQC methods. 相似文献
3.
Hadi Sayyadpour Farhad Behnamfar M. Hesham El Naggar 《Bulletin of Earthquake Engineering》2016,14(8):2385-2404
Usually for modeling of soil in a direct soil–structure interaction (SSI) problem, the equivalent linear soil properties are used. However, this approach is not valid in the vicinity of a foundation, where the soil experiences large strains and a high level of nonlinearity because of structural vibrations. The near-field method was developed and described in a companion paper to overcome this limitation. This method considers the effects of large strains and suggests a shear modulus and a damping ratio further modified in the near-field of a foundation. Validity and performance of this approach are evaluated, application examples are explained and the results of a parametric study about the role of soil and structure parameters in the extent of SSI effects on the nonlinear seismic response of structures are presented in this paper. One real existing and five, ten, fifteen and twenty story moment-resisting frame steel buildings with two different site conditions corresponding to firm and soft soils are considered and the responses obtained from the near-field method are compared with the recorded and rigorous responses. Moreover, various SSI modeling techniques are employed to investigate the accuracy and performance of each approach. The results show that the near-field method is a simple yet accurate enough approach for analysis of direct SSI problems. 相似文献
4.
Abstract In this paper a method for solving the equation for the mean magnetic energy <BB> of a solar type dynamo with an axisymmetric convection zone geometry is developed and the main features of the method are described. This method is referred to as the finite magnetic energy method since it is based on the idea that the real magnetic field B of the dynamo remains finite only if <BB> remains finite. Ensemble averaging is used, which implies that fields of all spatial scales are included, small-scale as well as large-scale fields. The method yields an energy balance for the mean energy density ε ≡ B 2/8π of the dynamo, from which the relative energy production rates by the different dynamo processes can be inferred. An estimate for the r.m.s. field strength at the surface and at the base of the convection zone can be found by comparing the magnetic energy density and the outgoing flux at the surface with the observed values. We neglect resistive effects and present arguments indicating that this is a fair assumption for the solar convection zone. The model considerations and examples presented indicate that (1) the energy loss at the solar surface is almost instantaneous; (2) the convection in the convection zone takes place in the form of giant cells; (3) the r.m.s. field strength at the base of the solar convection zone is no more than a few hundred gauss; (4) the turbulent diffusion coefficient within the bulk of the convection zone is about 1014cm2s?1, which is an order of magnitude larger than usually adopted in solar mean field models. 相似文献
5.
Introduction There are various factors affecting the propagation of earthquake waves. Usually these fac- tors include the earthquake source, the path and the site effects. Simulations of the earthquake wave propagation and the strong ground motion are an adequate way to exhibit these factors (Virieux, 1986; Levander, 1988; Frankel and Vidale, 1992; Frankel, 1993; Graves, 1993, 1996a; Olsen et al, 1995; Pitarka et al, 1996; Pitarka, 1999). The most popular numerical method in use is the gri… 相似文献
6.
Existing methods of cosmogenic nuclide burial dating perform well provided that sediment sources undergo steady rates of erosion and the samples experience continuous exposure to cosmic rays. These premises exert important limitations on the applicability of the methods. And yet, high mountain sediment sources are rife with transient processes, such as non-steady erosion by glacial quarrying and/or landsliding, or temporary cosmic-ray shielding beneath glaciers and/or sediment. As well as breaching the premises of existing burial dating methods, such processes yield samples with low nuclide abundances and variable 26Al/10Be ratios that may foil both isochron and simple burial-age solutions. P–PINI (Particle-Pathway Inversion of Nuclide Inventories) is a new dating tool designed for dating the burial of sediments sourced from landscapes characterized by abrupt, non-steady erosion, discontinuous exposure, and catchments with elevation-dependent 26Al/10Be production ratios. P–PINI merges a Monte Carlo simulator with established cosmogenic nuclide production equations to simulate millions of samples (10Be–26Al inventories). The simulated samples are compared statistically with 10Be–26Al measured in field samples to define the most probable burial age. Here, we target three published 10Be–26Al datasets to demonstrate the versatility of the P–PINI model for dating fluvial and glacial sediments. (1) The first case serves as a robust validation of P–PINI. For the Pulu fluvial gravels (China), we obtain a burial age of 1.27 ± 0.10 Ma (1σ), which accords with the isochron burial age and two independent chronometers reported in Zhao et al. (2016) Quaternary Geochronology 34, 75–80. The second and third cases, however, reveal marked divergence between P–PINI and isochron-derived ages. (2) For the fluvial Nenana Gravel (USA), we obtain a minimum-limiting burial age of 4.5 ± 0.7 Ma (1σ), which is compatible with unroofing of the Alaska Range starting ∼ 6 Ma, while calling into question the Early Pleistocene isochron burial age presented in Sortor et al. (2021) Geology 49, 1473–1477. (3) For the Bünten Till (Switzerland), we obtain a limiting burial age of <204 ka (95th percentile range), which conforms with the classical notion of the most extensive glaciation in the northern Alpine Foreland assigned to the Riss glaciation (sensu marine isotope stage 6) contrary to the isochron burial age presented in Dieleman et al. (2022) Geosciences, 12, 39. Discrepancies between P–PINI and the isochron ages are rooted in the challenges posed by the diverse pre-burial 26Al/10Be ratios produced under conditions characteristic of high mountain landscapes; i.e., non-steady erosion, discontinuous cosmic-ray exposure, and elevation-dependent 26Al/10Be production ratios in the source region, which are incompatible with the isochron method, but easily accommodated by the stochastic design of P–PINI. 相似文献
7.
Compared to other estimation techniques, one advantage of geostatistical techniques is that they provide an index of the estimation accuracy of the variable of interest with the kriging estimation standard deviation (ESD). In the context of radar–raingauge quantitative precipitation estimation (QPE), we address in this article the question of how the kriging ESD can be transformed into a local spread of error by using the dependency of radar errors to the rain amount analyzed in previous work. The proposed approach is implemented for the most significant rain events observed in 2008 in the Cévennes-Vivarais region, France, by considering both the kriging with external drift (KED) and the ordinary kriging (OK) methods. A two-step procedure is implemented for estimating the rain estimation accuracy: (i) first kriging normalized ESDs are computed by using normalized variograms (sill equal to 1) to account for the observation system configuration and the spatial structure of the variable of interest (rainfall amount, residuals to the drift); (ii) based on the assumption of a linear relationship between the standard deviation and the mean of the variable of interest, a denormalization of the kriging ESDs is performed globally for a given rain event by using a cross-validation procedure. Despite the fact that the KED normalized ESDs are usually greater than the OK ones (due to an additional constraint in the kriging system and a weaker spatial structure of the residuals to the drift), the KED denormalized ESDs are generally smaller the OK ones, a result consistent with the better performance observed for the KED technique. The evolution of the mean and the standard deviation of the rainfall-scaled ESDs over a range of spatial (5–300 km2) and temporal (1–6 h) scales demonstrates that there is clear added value of the radar with respect to the raingauge network for the shortest scales, which are those of interest for flash-flood prediction in the considered region. 相似文献
8.
In this present era of the Anthropocene, human activities affect hydrology and droughts. Quantifying this human influence improves our understanding and builds fundamental knowledge for water resource management. Analysis of observation data is useful in progressing this knowledge as these human activities and feedbacks are intrinsically included. Therefore, here we present an observation-based approach, the upstream–downstream comparison, to quantify changes in hydrological drought downstream of a human activity. We demonstrate this approach in a basin in northern Chile, where a reservoir was introduced. A sensitivity analysis is performed to assess how different choices of drought analysis threshold can affect the results and interpretation. We find that many commonly used choices do not exclude human activities from the threshold and therefore could be underestimating the change detected due to the human influence. The upstream–downstream comparison avoids this through the application of the upstream station threshold rather than the human-influenced downstream station. 相似文献
9.
Simulation method of near-fault pulse-type ground motion 总被引：1，自引：0，他引：1
Introduction With the development of the economy of China, it is possible to build large-span bridges, pipelines, dams and other lifeline structures in the seismically active regions or through the active faults. In addition, some isolated and energy diss… 相似文献
10.
A new data assimilation method called the explicit four-dimensional variational (4DVAR) method is proposed. In this method, the singular value decomposition (SVD) is used to construct the orthogonal basis vectors from a forecast ensemble in a 4D space. The basis vectors represent not only the spatial structure of the analysis variables but also the temporal evolution. After the analysis variables are ex-pressed by a truncated expansion of the basis vectors in the 4D space, the control variables in the cost function appear explicitly, so that the adjoint model, which is used to derive the gradient of cost func-tion with respect to the control variables, is no longer needed. The new technique significantly simpli-fies the data assimilation process. The advantage of the proposed method is demonstrated by several experiments using a shallow water numerical model and the results are compared with those of the conventional 4DVAR. It is shown that when the observation points are very dense, the conventional 4DVAR is better than the proposed method. However, when the observation points are sparse, the proposed method performs better. The sensitivity of the proposed method with respect to errors in the observations and the numerical model is lower than that of the conventional method. 相似文献
11.
Numerical Green’s function method:Application to quantifying ground motion variations of M7 earthquakes 
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下载免费PDF全文 The concept of "numerical Green’s functions" (NGF or Green’s function database) is developed. The basic idea is: a large seismic fault is divided into subfaults of appropriate size, for which synthetic Green’s functions at the surface (NGF) are calculated and stored. Consequently, ground motions from arbitrary kinematic sources can be simulated, rapidly, for the whole fault or parts of it by superposition. The target fault is a simplified, vertical model of the Newport-Inglewood fault in the Los Angeles basin. This approach and its functionality are illustrated by investigating the variations of ground motions (e.g. peak ground velocity and synthetic seismograms) due to the source complexity. The source complexities are considered with two respects: hypocenter location and slip history. The results show a complex behavior, with dependence of absolute peak ground velocity and their variation on source process directionality, hypocenter location, local structure, and static slip asperity location. We concluded that combining effect due to 3-D structure and finite-source is necessary to quan- tify ground motion characteristics and their variations. Our results will facilitate the earthquake hazard assessment projects. 相似文献
12.
Soil shear wave velocity (SWV) is an important parameter in geotechnical engineering. To measure the soil SWV, three methods are generally used in China, including the single-hole method, cross-hole method and the surface-wave technique. An optimized approach based on a correlation function for single-hole SWV measurement is presented in this paper. In this approach, inherent inconsistencies of the artificial methods such as negative velocities, and too-large and too- small velocities, are eliminated from the single-hole method, and the efficiency of data processing is improved. In addition, verification using the cross-hole method of upper measuring points shows that the proposed optimized approach yields high precision in signal processing. 相似文献
13.
IntroductionEarthquakepredictionisanundertakingofpublicwelfare,butearthquakecannotbesuccessfullypredictedatthepresentstageduetotechnologicalreasons.Howtoadaptthepresentsituationofearthquakepredictiontotheneedofsocietyisasubjectthatshouldbestudiedearnestly.Logicallyspeaking,themostimportantproblemindisasterpreventionisthemagnitudeofthecomingearthquake(becauseitconcernstherangeandinvestmentforprevention);Thesecondproblemisthemostdangerousseismiczone(becauseitconcernstheconcretearrangementforprev… 相似文献
14.
In this paper, we present an improvement to our previously published nearly analytic discrete method (NADM) to solve acoustic
and elastic wave equations. We compare the numerical errors of the improved NADM with the original NADM and also the fourth-order
Lax–Wendroff correction and present examples of three-component wave fields in 2D transversely isotropic media with strong
velocity contrasts. Comparing with the original NADM, we find that the improved method requires significantly less storage
space and can increase the time accuracy from second order of the original NADM to fourth order, while the space accuracy
remains the same as that of the original one. Theoretical analyses and numerical results suggest that our improved NADM is
suitable for large-scale numerical modelling as it can effectively suppress numerical dispersion and source-generated noises
caused by discretising wave equations when too-coarse grids are used. 相似文献
15.
Introduction A lot of work has been done in studying geological problems in terms of finite-element method (FEM). Assuming the material of fault as a perfect plastic one, WANG, et al (1980, 1982) simulated the transference of the larger earthquakes in North China by elasto-plastic FEM, the earthquakes are simulated by reducing frictional coefficients of the fault. YIN and ZHANG (1982) investigated the instability of earthquakes by FEM with strain-softening material model. WANG and C… 相似文献
16.
A statistical–dynamical model for estuary morphodynamics is presented and demonstrated with a case study on the Humber Estuary,
UK. The model presented here is hybrid in nature where simplified process dynamics are combined with a data-driven approach.
The modelling methodology uses an inverse technique to construct an unknown source function in the model-governing equation,
using historic measurements of estuary bathymetry. Spatial and temporal variability of the source function was established
using empirical orthogonal eigenfunction analysis. Predictions of estuary morphology are obtained by extrapolating the temporal
coefficients of the EOFs, in order to construct a predicted source function which is then used in the hybrid morphodynamic
equation to obtain the predicted estuary morphology. The model was applied to predict the morphological evolution of the Humber
Estuary over a period of a decade. Predicted results were compared with measured bathymetry data. The results reveal that
the model captured the decadal scale morphodynamic response of the estuary with a good qualitative accuracy, despite the simplified
approach used in the model. The accuracy of model predictions can be greatly improved if high-frequency bathymetry data are
available. 相似文献
17.
Mauro Dolce Elena Speranza Flavio Bocchi Chiara Conte 《Bulletin of Earthquake Engineering》2018,16(9):3791-3818
One major issue in the aftermath of a strong earthquake is the emergency management, which cannot be guaranteed if the physical components necessary for the operability of the contingency plan are either damaged, unusable or inaccessible. In order to assess the physical efficiency of the emergency system on which a contingency plan is based, the I.OPà.CLE method (Indices for evaluation of the Operational efficiency of Limit Condition Emergency) has been set up by the Italian Civil Protection Department. It is basically aimed at supporting civil protection decision makers in evaluating emergency systems and establishing strategies and priorities concerning strengthening interventions at national, regional or municipality level. The method must be potentially applied to any of the around 8000 municipalities all over Italy, and then it must refer to a minimum information dataset readily available for any municipality. Therefore, I.OPà.CLE has been specifically tailored for the minimum standard information that is provided by the analysis of Limit Condition for Emergency, as formulated in 2012 by the Italian Civil Protection Department. This analysis defines the standard framework of the physical layout of a municipal seismic emergency plan, relying on a limited number of information. Notwithstanding the numerically extensive target and limited amount of information available, the ambition of I.OPà.CLE is to perform simplified analyses without renouncing to rigor in the methodology. The present paper illustrates the analytic formulation of I.OPà.CLE and its capabilities, as well as two real examples. In the conclusion, future upgrading of the model are discussed, even in relation to the availability of further pieces of information. 相似文献
18.
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19.
A new method for dynamic inversion of anisotropic equations 总被引：1，自引：0，他引：1
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20.
Introduction The migrationof electromagnetic field is like that of elastic wave in seismic prospecting, butthere are some differences between them (Lee et al, 1989). The elastic wave field satisfies thegeneral wave equation, while the electromagnetic field in our study satisfies the diffusion equation.Both the electromagnetic field and the elastic wave field have a similar mechanism. The imagingfunction named map can characterize the interface of different mediums (MA, 1989), that is … 相似文献