共查询到20条相似文献，搜索用时 80 毫秒
1.
Hydrogeology: time for a new beginning? 总被引：1，自引：0，他引：1
Phillips FM 《Ground water》2002,40(3):217-219
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Luís Margalho Raquel Menezes Inês Sousa 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(5):1307-1321
In Europe, since 1990, a survey on environmental monitoring has been taking place every 5 years, using moss samples to study the distribution of heavy metal concentration and assess contamination sources, resulting on the identification of statistical association of several heavy metal concentrations in mosses. With this work, we propose an extension of an existing spatio-temporal model, introduced in Høst et al. (JASA 90(431):853–861, 1995), allowing for prediction at unsampled locations of pollution data in the presence of covariates related to each country specificities, when separately modelling the spatial mean field, the spatial variance field and the space–time residual field. Moreover, this model allows to estimate an interpolation error, as an accuracy measure, derived dependently on the case study. For a validation purpose, a simulation study is conducted, showing that the use of the proposed model leads to more accurate prediction values. Results obtained by the proposed methodology for the most recent available survey, are compared with results obtained with no temporal information, namely when Ordinary Kriging, according to the definition in Cressie (Statistics for spatial data, Wiley, New York, 1993), is used to derive illustrative prediction maps based only on the most recent data. An exercise of cross-validation is performed relative to each of the scenarios considered and the average interpolation errors are presented. While assessing interpolation errors, we conclude that the monitoring specificities of each country and the information of preceding surveys allow for more accurate prediction results. 相似文献
3.
Onthephysicalmodelofearthquakeprecursorfieldsandthemechanismofprecursors′time┐spacedistribution（Ⅱ）Ho
梅世蓉 《地震学报(英文版)》1996,(1)
Ｏｎｔｈｅｐｈｙｓｉｃａｌｍｏｄｅｌｏｆｅａｒｔｈｑｕａｋｅｐｒｅｃｕｒｓｏｒｆｉｅｌｄｓａｎｄｔｈｅｍｅｃｈａｎｉｓｍｏｆｐｒｅｃｕｒｓｏｒｓ′ｔｉｍｅ┐ｓｐａｃｅｄｉｓｔｒｉｂｕｔｉｏｎ（Ⅱ）Ｈｏｗｄｏｔｈｅｓｔｒｅｓａｎｄｓｔｒａｉｎｆｉｅｌｄ... 相似文献
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The brief theories of wavelet analysis and Hilbert-Huang transform (HHT) are introduced firstly in the present paper. Then several signal data were analyzed by using wavelet and HHT methods, respectively. The comparison shows that HHT is not only an effective method for analyzing non-stationary data, but also is a useful tool for examining detailed characters of time history signal. 相似文献
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Introduction At present, the current probabilistic method of seismic hazard analysis in the world is gener-ally adopted in seismic safety evaluation (Cornell, 1968). It supposed that earthquake occurrence conforms to the segmented Poisson distribution model in time and space and the proportional rela-tion among earthquakes of various magnitudes obeys the cut-exponential distribution law in a sta-tistical area in compiling Seismic Intensity Zoning Map in China (1990) owing to the temporal- sp… 相似文献
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José M. Angulo Francisco J. Esquivel 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(5):1187-1206
Different approaches and tools have been adopted for the analysis and characterization of regional seismicity based on spatio–temporal series of event occurrences. Two main aspects of interest in this context concern scaling properties and dimensional interaction. This paper is focused on the statistical use of information-theoretic concepts and measures in the analysis of structural complexity of seismic distributional patterns. First, contextual significance is motivated, and preliminary elements related to informational entropy, complexity and multifractal analysis are introduced. Next, several technical and methodological extensions are proposed. Specifically, limiting behaviour of some complexity measures in connection with generalized dimensions is established, justifying a concept of multifractal complexity. Under scaling behaviour, a mutual-information-related dependence coefficient for assessing spatio–temporal interaction is defined in terms of generalized dimensions. Also, an alternative form of generalized dimensions based on Tsallis entropy convergence rates is formulated. Further, possible incorporation of effects, such as earthquake magnitude, is achieved in terms of weighted box-counting distributions. Different aspects in relation to the above elements are analyzed and illustrated using two well-known series of seismic event data of an underlying different nature, occurred in the areas of Agrón (Granada, Spain) and El Hierro (Canary Islands, Spain). Finally, various related directions for continuing research are indicated. 相似文献
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IntroductionTime reversal effect is a kind of reversed dynamic process in a limited space or time interval, which can be realized artificially by resetting the boundary and loading conditions. In this case the time seems to be reversed and such effect therefore is called time reversal effect, which was first proposed in and applied to the field of ultrasonic. Although the focusing of ultrasonic wave has powerful effect, it is difficult to focus in an anisotropic or homogeneous medium. Fink (19… 相似文献
9.
This work presents a random field model of disease attribute (incidence, mortality etc.) that transfers the study of the attribute distribution from the original spatiotemporal domain onto a lower-dimensionality traveling domain that moves along the direction of disease velocity. The partial differential equations connecting the disease attribute covariances in the original and the traveling domain are derived with coefficients that are functions of the disease velocity. These equations offer epidemiologic insight concerning the strength of the space–time dependence between the disease attribute values in the two domains. The traveling disease model has certain theoretical and computational advantages in the study and prediction of space–time disease attribute distributions in conditions of uncertainty. Estimates of the disease attribute are derived in the traveling domain and then used to generate maps of space–time disease attribute distribution in the original domain. The theoretical model is illustrated and additional insight is gained by means of a numerical mortality simulation study, which shows that the proposed model is at least as accurate but computationally more efficient than mainstream mapping techniques of higher dimensionality. These findings concerning the very good predictability of the proposed model also strongly support its adequacy to represent the space–time mortality distribution. 相似文献
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M. D. Ruiz-Medina R. M. Espejo M. D. Ugarte A. F. Militino 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(4):943-954
Spatio–temporal statistical models have been proposed for the analysis of the temporal evolution of the geographical pattern of mortality (or incidence) risks in disease mapping. However, as far as we know, functional approaches based on Hilbert-valued processes have not been used so far in this area. In this paper, the autoregressive Hilbertian process framework is adopted to estimate the functional temporal evolution of mortality relative risk maps. Specifically, the penalized functional estimation of log-relative risk maps is considered to smooth the classical standardized mortality ratio. The reproducing kernel Hilbert space (RKHS) norm is selected for definition of the penalty term. This RKHS-based approach is combined with the Kalman filtering algorithm for the spatio–temporal estimation of risk. Functional confidence intervals are also derived for detecting high risk areas. The proposed methodology is illustrated analyzing breast cancer mortality data in the provinces of Spain during the period 1975–2005. A simulation study is performed to compare the ARH(1) based estimation with the classical spatio–temporal conditional autoregressive approach. 相似文献
11.
F. Martínez-Ruiz J. Mateu F. Montes E. Porcu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(4):519-526
Dynamic life tables arise as an alternative to the standard (static) life tables with the aim of incorporating the evolution
of mortality over time. These tables can be considered as a two-way table on a grid equally spaced in either the vertical
(age) or horizontal (year) directions, and the data can be decomposed into a deterministic large-scale variation (trend) plus
a stochastic small-scale variation (residuals). In this context, space–time geostatistical methods can be used for fitting
and predicting the dynamic mortality. We use four different space–time covariance functions for fitting and predicting mortality
in Spain during the period 1980–2005. In particular, we aim at showing the behavior of separable versus nonseparable fitted
structures on one hand, and the behavior of simple structures given by combinations of products and sums versus more complicated
negative structures on the other hand. 相似文献
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IntroductionPlumb line deflection (PLD) express the incline between the geoid and the surface of ellipsoidal earth, i.e., the deflection of the real plumb line of calculating point to the normal direction of the corresponding point in the ellipsoidal surface. It varied in the range of about 3(~5( generally, and the largest value will be 20(~30( in spatial domain. Plumb line is closely related to spatial distribution of gravity field on the earth surface. PLV of a point on the earth surface c… 相似文献
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M. Bohorquez J. Mateu L. Diaz 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(4):1011-1022
The differentiability of a random field has a direct relationship with the differentiability of its covariance function. We review the concept of differentiability of space–time covariance models and random fields, and its implications on predictions. We analyze the change of behavior of the covariance function at the origin and at different space–time lags away from the origin, by using the concept of smoothness which can be considered the geometrical view of the differentiability. We propose a way to measure the smoothness of any covariance function, and apply it to purely spatial and space–time covariance functions. 相似文献
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The seismic wave consists of many seismic phases, which contain rich geophysical information from the hypocenter, medium of seismic wave passing through and so on. It is very important to detect and pick these seis-mic phases for understanding the mechanism of earthquake, the Earth structure and property of seismic waves. In order to reduce or avoid the loss resulted from the earthquake, one of the important goals of seismic event detect-ing is to obtain its related information before and afte… 相似文献
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Introduction Prediction of RIS includes earlier stage prediction and seismic tendency prediction. In earlier stage, the prediction is to predict the possibility and maximum magnitude of RIS before reservoir are built up. It is made up on the basis of geological condition and the definite method and the statistical model method are usually used. The definite method by analogy with geological condi-tion is to analyze and sum up the main conditions of RIS. Using the main conditions compared w… 相似文献
16.
Paul Sava 《Geophysical Prospecting》2016,64(3):581-594
Reverse time migration backscattered events are produced by the cross‐correlation between waves reflected from sharp interfaces (e.g., salt bodies). These events, along with head waves and diving waves, produce the so‐called reverse time migration artefacts, which are visible as low wavenumber energy on migrated images. Commonly, these events are seen as a drawback for the reverse time migration method because they obstruct the image of the geologic structure, which is the real objective for the process. In this paper, we perform numeric and theoretical analysis to understand the reverse time migration backscattering energy in conventional and extended images. We show that the reverse time migration backscattering contains a measure of the synchronization and focusing information between the source and receiver wavefields. We show that this synchronization and focusing information is sensitive to velocity errors; this implies that a correct velocity model produces reverse time migration backscattering with maximum energy. Therefore, before filtering the reverse time migration backscattered energy, we should try to obtain a model that maximizes it. 相似文献
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ｎｔｒｏｄｕｃｔｉｏｎＴｈｅｃｕｒｅｎｔｐｒｏｂａｂｉｌｉｓｔｉｃｍｅｔｈｏｄｏｆｓｅｉｓｍｉｃｈａｚａｒｄａｎａｌｙｓｉｓｉｎｔｈｅｗｏｒｌｄｉｓｇｅｎｅｒａｌｙａｄｏｐｔｅｄｉｎｓｅｉｓｍｉｃｚｏｎｉｎｇ．Ｉｔｓｕｐｐｏｓｅｄｔｈａｔｅａｒｔｈｑ... 相似文献
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ＴｒａｖｅｌｔｉｍｅｔｏｍｏｇｒａｐｈｙｉｎｖｅｒｓｉｏｎａｎｄｔｈｅｄｅｅｐｓｔｒｕｃｔｕｒｅｏｆｔｈｅｓｏｕｔｈｅｒｎＴｉｂｅｔＱＩＮＧ－ＴＩＡＮＬＵ１）（吕庆田）,ＭＥＩ－ＪＩＡＮＧ１）（姜枚）,ＫＡＩ－ＹＩＭＡ１）（马开义）,Ａ．Ｈｉｒｎ２... 相似文献
20.
Zhang Liyan Liu Yang 《应用地球物理》2006,3(1):18-26
Pseudo-offset migration （POM） is a new method for prestack time migration of converted waves that improves on equivalent-offset migration （EOM）. The mapping of POM is different than EOM but the purpose of the two methods is to map the input samples to the common conversion scatter point （CCSP） gathers. This paper introduces the principles of the two migration methods and model parameter sensitivity tests for both POM and EOM. At large offset-to-depth ratios the hyperbolic approximation, the three-term approximation and the double square root （DSR） equation are used to NMO-correct the mapped POM gathers to obtain more accurate migration velocities. These equations were derived and calculated by small pseudo offset. POM is then used to image complex structure and prestack time migration. 相似文献