A computational approach for the analysis of changes in polygon distributions

 This paper develops a computational method for analyzing changes in polygon distributions. Unmovable polygons that change discontinuously without explicit functional linkage information are discussed. Six types of primitive events are used to describe the change: 1) generation, 2) disappearance, 3) expansion, 4) shrinkage, 5) union, and 6) division. The change of polygon distributions is decomposed into a combination of these events. A computational procedure for deducing a set of events from polygon distributions of two times is proposed. The method is applied to the analysis of the spatial competition between the major and small chains of convenience stores in Tokyo, Japan. Some empirical findings are shown. Received: 3 August 2000 / Accepted: 6 February 2001     

基于结构特征的地图信息识别与提取

叙述了基于结构特征的地图信息识别与提取的方法 ,讨论了收缩变换、扩张变换、细化、Hough变换、RLS变换和特征点提取等各种特征提取算法。     

Modal identification of structures from ambient vibration,free vibration,and seismic response data via a subspace approach

This work presents a unified procedure for determining the natural frequencies, modal damping ratios and modal shapes of a structure from its ambient vibration, free vibration and earthquake response data. To evaluate the coefficient matrices of a state‐space model, the proposed procedure applies a subspace approach cooperating with an instrumental variable concept. The dynamic characteristics of a structure are determined from the coefficient matrices. The feasibility of the procedure is demonstrated through processing an in situ ambient vibration measurement of a five‐storey steel frame, an impulse response measurement of a three‐span continuous bridge, and simulated earthquake responses of five‐storey steel frames from shaking table tests. The excellent agreement of the results obtained herein with those published previously confirms the feasibility of the present procedure. Copyright © 2001 John Wiley & Sons, Ltd.     

底侵玄武质下地壳的熔融:来自安徽沙溪adakite质富钠石英闪长玢岩的证据

沙溪石英闪长玢岩具有高Al2O3,Sr/Y,La/Yb，低Y，Yb,Sr正异常，Eu弱负异常－正异常，表现出与adakite岩类似的地球化学特征，与庐枞火山盆地双庙组粗面玄武岩的微量元素特征和Nd-Sr同位素组成类似，研究表明：（1）沙溪侵入岩不是由俯冲的洋壳熔融形成，而是由底侵的玄武质下地壳熔融形成，该玄武质下地壳的物质来源与双庙组玄武岩的来源相似，都为富集地幔；（2）燕山晚期，长江中下游地区可能存在玄武质岩浆的底侵作用，地壳发生垂向增生，沙溪地区地壳厚度曾大于40km，但白垩纪至现在，沙溪地区地壳明显减薄；（3）沙溪铜（金）矿床不是与大洋板片俯冲有关的斑岩铜（金）矿床，而可能是与底侵的玄武质下地壳熔融有关的斑岩铜（金）矿床。     

56Ma:华南岩石圈伸展和南海张开的重要转折时间

广东四会 吴川断裂带茂名、三水、河源、连平 南雄等盆地火山岩的年代学、岩石学和钕同位素资料表明 ,在 92～ 38Ma存在连续的火山作用 ,并在始新世早期 (约 5 6Ma)火山作用源区从下地壳突然转向上地幔 ,标志着华南岩石圈在这一时间出现大规模伸展减薄。这一重大转折事件与菲律宾海、南海等东亚边缘海盆的最早张开密切相关。     

Mode‐acceleration approach to seismic response of multiply‐supported secondary systems

A mode‐acceleration approach has been proposed for estimating the seismic response of a linear, classically‐damped, multiply‐supported secondary system within the framework of a power spectral density function (PSDF)‐based stochastic approach, while the primary system is linear and classically‐damped. Response transfer functions have been formulated in terms of chosen numbers of fixed‐base modes of the primary and secondary systems. The proposed approach does not involve the determination of combined system properties, and is applicable to the secondary systems with high mass ratios also. Through a few example primary–secondary systems and an example band‐limited white noise excitation, it has been shown that this approach leads to reasonably accurate results when only a few primary and secondary modes are to be considered. The proposed formulation has been used to obtain input data for a decoupled response spectrum analysis of secondary systems. This data accurately accounts for the effects of interaction between the primary and secondary systems. It is shown to lead to substantial reductions in the errors associated with the envelope spectrum method in the case of moderately heavy to heavy secondary systems and when the spatial coupling does not play a major role. Copyright © 2002 John Wiley & Sons, Ltd.     

Seismic Hazard Assessment for the Taiwan Region on the Basis of Recent Strong-Motion Data and Prognostic Zonation of Future Earthquakes

The paper describes an integrated approach to seismic hazard assessment, which was applied for the Taiwan region. First, empirical modelsfor ground motion estimation in the region were obtained on the basisof records from recent (1993-1999) earthquakes. The databaseincludes strong-motion data collected during the recent Chi-Chiearthquake (M=7.6, 21 September 1999) and large (M=6.8)aftershocks. The ground-motion database was also used for evaluationof generalised site amplification functions for typical soil classes(B, C and D). Second, the theoretical seismic catalogue (2001–2050)for the Taiwan region had been calculated using the 4D-model(location, depth, time) for dynamic deformation of the Earth' crustand 5D-model (location, depth, time, magnitude) for seismic process.The models were developed on the basis of available geophysical andgeodynamic data that include regional seismic catalogue. Third, theregion & site & time-dependent seismic analysis, which is basedon schemes of probable earthquake zones evaluated from the theoreticalcatalogue, regional ground motion models, and local site responsecharacteristics, has been performed. The seismic hazard maps arecompiled in terms of Peak Ground Acceleration (PGA) and ResponseSpectra (RS) amplitudes. The maps show distribution of amplitudesthat will not be exceeded with certain probability in condition oftypical soil classes during all possible earthquakes that may occur inthe region during time period of 2003–2025. The approach allowsintroducing new parameter that describes dependency of seismichazard on time, so-called 'period of maximum hazard'. Theparameter shows the period, during which every considered sitewill be subjected by the maximum value of ground motioncharacteristic (PGA or RS).     

Xenolith evidence for polybaric melting and stratification of the upper mantle beneath South China

Mantle xenoliths from Hainan and Qilin, South China have been studied to constrain the nature of the upper mantle and mantle processes beneath a continental margin. The extremely low Ti (160–245 ppm) contents in clinopyroxenes from some spinel lherzolites, indicative of high degrees of partial melting are inconsistent with the relatively high clinopyroxene modes (7.4–13%) in these samples. This inconsistency could be due to polybaric melting that started in the garnet stability field, then, after the breakdown of garnet to pyroxene and spinel, continued in the spinel stability field. Polybaric melting, due to adiabatic decompression of upwelling mantle, would leave a residual mantle in which the degree of depletion decreases with depth. The predicted stratified lithospheric mantle is evidenced by the negative correlation between the forsterite content in olivine and the equilibration temperature, proportional to the depth in the lithosphere from which the xenolith was derived. The lower part of the lithospheric mantle beneath South China consists predominantly of fertile and moderately depleted peridotites, which are either devoid of LREE enrichment, or show the trace element signature of incipient metasomatism, and plot within the Phanerozoic mantle domain. In contrast, the upper part of the mantle contains harzburgite and cpx-poor lherzolite, which are strongly affected by metasomatism of melt/fluid of highly variable composition. The anomalously high orthopyroxene mode (up to 47%) makes some of these refractory samples compositionally similar to the Proterozoic/Archean mantle. Their low equilibrium temperature (800–900 °C) points to the presence of old lithospheric relicts in the uppermost mantle beneath South China. Such lithosphere architecture may have resulted from partial replacement of Archean–Proterozoic lithosphere by asthenosphere that rose adiabatically subsequent to lithospheric thinning during the Cenozoic.     

Origin of the regional stress in the North German basin: results from numerical modelling

We use a thin sheet approach to investigate the effects induced by the Alpine collision on the deformation and regional stress in northern Europe, with special emphasis on the NE German Basin. Here new seismic crustal studies indicate a flexural-type basin, which may have been induced by compressive forces transmitted from the south, due to the Alpine orogeny. Finite-element techniques are used to solve the equations for the deformation of a continuum described by a linear creep rheology and a spatial resolution of about 0.5°. The model has been constrained by stress and seismic data. We show that a relatively strong lithosphere below the northern margin of the German Basin, at the transition with the Baltic Shield, may explain the characteristic regional stress field, in particular the fan-like pattern which is observed within the region. Furthermore, the predicted strain rate pattern resembles the seismically recognizable undeformed area of the North German Basin.