The connection of geodynamics with seismicity patterns     

Adrian E. Scheidegger 《Natural Hazards》1988,1(1):5-13

When a study is to be made of seismic risks, the present-day geodynamic conditions are of fundamental importance: Earthquakes do not happen by themselves, they do have a cause. The cause of earthquakes is that the tectonic stresses exceed a critical limit. The build-up of these stresses is conditioned by the geodynamic processes occurring in the region in question. A knowledge of the geodynamics characteristic of a region is therefore fundamental for seismic risk studies. The general methodology for making such a geodynamic study is based on the entire set of manifestations of the plate-tectonic conditions of that region: these include the mechanism of earthquakes, the stresses observed in mines, the orientation of surface joints and even the direction of river valleys. Examples of geodynamic studies and their bearing on seismic risks are shown from various areas of the world, notably from China, India, and Colombia.  相似文献   

Vibrational spectra,lattice dynamics and chemical constitution of oxides     

Adrian N. Lazarev 《Physics and Chemistry of Minerals》1988,16(1):61-72

The relationships among lattice dynamics of oxides and their chemical constitution are discussed in terms of the concept of dynamic crystal chemistry. A new approach to the design of a dynamic model of an ionic-covalent crystal combining molecular force constants with explicit treatment of long-range electrostatic forces in a lattice is outlined and its applications exemplified. The conditions of introduction of scaled quantum chemical force constants of a suitable molecular system into the secular equation for lattice vibrations are determined rigorously. The importance of unified treatment of stability conditions and various dynamic properties of crystals including phonon spectra, macroscopic elastic and piezoelectric constants etc., is emphasized. Several results of ab initio quantum chemical SCF computations by the gradient method for molecular species containing silicon-oxygen bonds are presented and are used to explain some empirical regularities in silicate structures.  相似文献   

Non-linear earthquake response of concrete gravity dams part 1: Modelling     

Bahaa El-Aidi  John F. Hall 《地震工程与结构动力学》1989,18(6):837-851

A finite element procedure to model the non-linear earthquake response of concrete gravity dam systems is presented. A two-dimensional idealization is adopted for the dam and water in order to simplify the analysis and reduce the computational effort. The foundation of the dam is modelled as a rigid rectangular massless plate attached to a three-dimensional viscoelastic half-space. The non-linear behaviour is represented by smearing techniques and includes tensile cracking with subsequent opening, closing and sliding, as well as water cavitation in the reservoir. Special treatments are applied to suppress spurious oscillations in the water response associated with cavitation and to prevent cracks in the dam from spreading into wide zones. Experience from non-linear analyses is cited as it affects the design of the algorithm.  相似文献   

Going Home: The Migration of Puerto Rican-Born Women from the United States to Puerto Rico*     

Adrian J. Bailey  Mark Ellis 《The Professional geographer》1993,45(2):148-158

This paper analyzes the migration of Puerto Rican-born women from the United States to Puerto Rico using longitudinal data. We hypothesize that sojourn length in the United States is a function of both structural (macro-level economic and cultural factors) and behavioral (micro-level life-cycle experiences and personal attributes) variables. We test these hypotheses by estimating a proportional hazards model. The parameter estimates of this model indicate that sojourn length in the United States, and thus the decision to return to Puerto Rico, is a function of wage trends and community characteristics on the mainland plus a number of individual attributes that include education, marriage, and childbirth.  相似文献   

Whisker crystals of the mineral ettringite     

G. Macleod  Dr. A. J. Hall 《Mineralogy and Petrology》1991,43(3):211-215

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The Faunal Remains from Evron Quarry in Relation to Other Lower Paleolithic Hominid Sites in the Southern Levant     

Eitan Tchernov  Liora Kolska Horwitz  Avraham Ronen  Adrian Lister 《Quaternary Research》1994,42(3)

The mammalian assemblage and archaeological finds from the Lower Palaeolithic hominid site of Evron Quarry, situated on the northern coastal plain of Israel, are described and discussed. In their lithic and faunal composition, the sites of Latamne (QfIII) (Latamne Formation, Orontes, Syria) and Sitt Markho (Nahr elKebir, Syria) resemble Evron and are probably contemporaneous. It is suggested here, based on their lithic and faunal composition, that these sites may be chronologically closer to the site of Ubeidiya ('Ubeidiya Formation, Jordan Valley, Israel; 1.4 myr) than to the sites of Gesher Benot Ya'akov (dated as <800,000 yr B.P.), which differs in both aspects from Evron. The mammalian faunule from Evron comprises a biogeographical mixture, a result of biotic exchanges with Africa, the Oriental region, and the Palaearctic. This exchange may have been associated with a post-'Ubeidiya hominid dispersal, either from Africa or south Asia via the Levantine "corridor."  相似文献   

Telecommunications and the Large City-Small City Divide: Evidence from Indiana Cities*     

Patrick Alles  Adrian Esparza  Susan Lucas 《The Professional geographer》1994,46(3):307-316

Urban systems are increasingly dominated by large cities that house a disproportionate share of telecommunications infrastructure. This paper investigates whether telecommunications is defining a technological divide between large and smaller cities. The paper provides a conceptual basis for large-city dominance and presents the results of surveys that investigate the use of telecommunications in medium and small Indiana cities. The survey data indicate that telecommunications is used by the set of Indiana cities, but is less prevalent among the set of smallest cities. Chi-square tests, however, suggest that city size does not adequately explain these variations in use.  相似文献   

Response of jointed arches to earthquake excitation     

John F. Hall  Michael J. Dowling 《地震工程与结构动力学》1985,13(6):779-798

An efficient method for accurately modelling the gradual opening and closing of joints in two-dimensional slabs and arches has been devised. The method is used in computing the earthquake response of an arch which is a representative horizontal cross-section of a concrete arch dam. Responses of the arch with and without joints are compared to assess the effect of joint opening. An extension to three-dimensional arch dams is proposed.  相似文献   

The significance of surface joints     

Adrian E. Scheidegger 《Surveys in Geophysics》1985,7(3):259-271

This brief review demonstrates the significance, on a global scale, of joints as shearing surfaces in the neotectonic stress field. Thus, the principal directions of the neotectonic stress field can be determined by a statistical treatment of joint orientation data. These principal stress directions agree with those postulated from plate tectonic theory in every case, on five continents.  相似文献   

Buried trees,water table fluctuations,and 3000 years of changing climate in west-central Oklahoma     

Stephen A. Hall  Christopher Lintz 《Quaternary Research》1984,22(1):129-133

A sequence of radiocarbon-dated buried trees, buried soils, a carbonate zone, and a molluscan fauna from Carnegie Canyon indicate that between 3200 and 2600 yr B.P. the climate of west-central Oklahoma was drier than today. A high water table accompanied a period of moister climate 2000 to 1000 yr B.P. The water table dropped after 1000 yr B.P. due to a change toward dry conditions.  相似文献