沈阳市浑南新区场地地震易损性分析     

万波  廖旭  吴明大  郑双成 《东北地震研究》2002,18(1):45-51

地震易损性分析是进行场地抗震性能划分的一种有效方法。根据沈阳市浑南新区的地震、地质和地貌特点 ,选取场地地基土、断层、地表地震动参数、地下水埋深和第四系厚度作为场地地震易损性分析的因素 ,并采用灰色统计方法对专家意见进行分析以确定易损性指数系数。计算结果表明 ,浑南新区的大部分地区属于抗震有利地段 ,占总面积的 81 6 8% ,抗震不利地段只占 1 8 32 %。  相似文献   

Rare-gas dating,III. Evaluation of a double-spiking procedure for potassium-argon dating     

C.R. Macedo  C.V. Costa  J.T. Ferreira  M.P. Ferreira  J.H. Reynolds 《Earth and Planetary Science Letters》1977,34(3):411-418

A double-spike method for KAr dating is described. Use of long-lived³⁹Ar in addition to the usual³⁸Ar in the spike permits argon isotopic discrimination occurring after insertion of the spike to be monitored at the same time as ages are determined. A “bootstrap” (self-contained) method of calibrating the spike for isotopic composition is described which, when used appropriately, gives final ages which are independent of the published isotopic composition of the terrestrial atmospheric argon used as a comparison gas. The method calls for a mass spectrometer which resolves adjacent isotopes to a high degree. We have tested the method nevertheless with a mass spectrometer of relatively low resolving power, the AEI MS-10, and found it to be successful in part and without any disadvantages with respect to conventional techniques in those instances where the method fails because of insufficient resolution. That is, we find the discrimination factor inferred in runs on young rocks and blanks to be valid and useful. That factor changes by as much as 1.3% over the life of a filament in the ion source of the MS-10, proving that close control of the discrimination factor is essential for analytical precision with the instrument. These assertions are documented graphically with a compilation of data which represents more than two years experience with the method. We also report measurements of the mass discrimination of the MS-10 and its linearity with mass which indicate that the latter quantity is acceptable when the repeller voltage for the ion source is close to +1 V and is unacceptable otherwise. The spike material is available, upon request, to those laboratories which decide firmly to undertake further testing of the method.  相似文献   

Hostels for African migrants in greater Johannesburg     

Mr. G. H. Pirie  Ms. M. da Silva 《GeoJournal》1986,12(2):173-180

Greater Johannesburg's hostels accomodate some 50 000 African migrants in buildings which are prominent features of the residential landscape. Hostelling was conceived and implemented by the infant town council in 1912 partly to end slum dwelling. Subsequently two main phases of construction followed promulgation of parliamentary acts and involved placing more hostels in African townships than in white areas. The bleak and regimented world of the hostel speaks to a practice of providing migrants with the bare minimum shelter and amenities which will avoid disruption of migrancy. The socially unnatural and sometimes violent life in hostels tells of the conditions which migrants will endure so as to secure a precious toehold in the metropolitan economy.  相似文献   

On intermediate-term earthquake prediction in central Italy     

V. I. Keilis-borok  I. V. Kuznetsov  G. F. Panza  I. M. Rotwain  G. Costa 《Pure and Applied Geophysics》1990,134(1):79-92

The Time of Increased Probability (TIP) for the occurrence of a strong earthquake is determined in Central Italy. This is done with an algorithm that has been successfully applied in other regions of the world (algorithm CN, from the initials of California and Nevada, where the first diagnoses of TIPs were made). The use of normalized functions allows direct application of the orginal algorithm to the new region being studied, without anyad hoc adjustment of the parameters.Retrospective analysis carried on until 1986 shows that TIPs occupy 26 percent of the total time considered and precede four out of five strong earthquakes. Forward monitoring indicates the possible existence of a TIP started in May 1988.Several tests indicate that the results obtained are quite stable, even when using catalogues from different agencies. Apart from obvious practical interest, this research is essential for the worldwide investigation of self-similarity in the origin of strong earthquakes.  相似文献   

The evolution of clusters in the CLEF cosmological simulation: X-ray structural and scaling properties     

Scott T. Kay  Antonio C. da Silva  Nabila Aghanim  Alain Blanchard  rew R. Liddle  Jean-Loup Puget  Rachida Sadat  Peter A. Thomas 《Monthly notices of the Royal Astronomical Society》2007,377(1):317-334

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A review of recent results on ocean acoustic wave propagation inrandom media: basin scales     

Colosi  J.A. Baggeroer  A.B. Birdsall  T.G. Clark  C. Cornuelle  B.D. Costa  D. Dushaw  B.D. Dzieciuch  M.A. Forbes  A.M.G. Howe  B.M. Menemenlis  D. Mercer  J.A. Metzger  K. Munk  W. Spindel  R.C. Worcester  P.F. Wunsch  C. 《Oceanic Engineering, IEEE Journal of》1999,24(2):138-155

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Extended star formation history of the star cluster NGC 2154 in the Large Magellanic Cloud     

G. Baume  G. Carraro †  E. Costa  R. A. Méndez  L. Girardi 《Monthly notices of the Royal Astronomical Society》2007,375(3):1077-1086

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1.94–1.93 Ga charnockitic magmatism from the central part of the Guyana Shield, Roraima, Brazil: Single-zircon evaporation data and tectonic implications     

Lêda Maria Fraga  Moacir Jose Buenano Macambira  Roberto Dall&#x;Agnol  Joo Batista Sena Costa 《Journal of South American Earth Sciences》2009,27(4):247-257

Age and origin of the charnockitic rocks of the central part of the Guyana Shield have been a matter of discussion. These rocks have been interpreted either as Transamazonian granulites metamorphosed around 2.02 Ga or as 1.56 Ga old igneous charnockites. Recently, most of the Roraima charnockitic rocks have been recognized as igneous rocks and included into the Serra da Prata Suite (SPS). Five Pb–Pb single-zircon evaporation ages were obtained for samples representative of different facies of the SPS and these constrained the age of the charnockitic magmatism between 1943 ± 5 Ma and 1933 ± 2 Ma. This charnockitic magmatism may be related to a post-collisional setting after the evolution of the Cauarane-Coeroeni Belt (～2.00 Ga), or may represent a post-collisional (or intracontinental?) magmatism related to orogenic activities along the plate margins around 1.95–1.94 Ga.  相似文献   

Morphogenesis of the SW Balearic continental slope and adjacent abyssal plain,Western Mediterranean Sea     

Angelo Camerlenghi  Daniela Accettella  Sergio Costa  Galderic Lastras  Juan Acosta  Miquel Canals  Nigel Wardell 《International Journal of Earth Sciences》2009,98(4):735-750

We present the seafloor morphology and shallow seismic structure of the continental slope south-east of the Balearic promontory and of the adjacent Algero-Balearic abyssal plain from multibeam and chirp sonar data. The main purpose of this research was to identify the sediment pathways from the Balearic promontory to the Algero-Balearic deep basin from the Early Pliocene to the Present. The morphology of the southern Balearic margin is controlled by a SW–NE structural trend, whose main expressions are the Emile Baudot Escarpment transform fault, and a newly discovered WSW–ENE trend that affects the SW end of the escarpment and the abyssal plain. We relate the two structural trends to right-lateral simple shear as a consequence of the Miocene westward migration of the Gibraltar Arc. Newly discovered steep and narrow volcanic ridges were probably enabled to grow by local transtension along the transform margin. Abyssal plain knolls and seahills relate to the subsurface deformation of early stage halokinetic structures such as salt rollers, salt anticlines, and salt pillows. The limited thickness of the overburden and the limited amount of deformation in the deep basin prevent the formation of more mature halokinetic structures such as diapirs, salt walls, bulbs, and salt extrusions. The uppermost sediment cover is affected by a dense pattern of sub-vertical small throw normal faults resulting from extensional stress induced in the overburden by subsurface salt deformation structures. Shallow gas seismic character and the possible presence of an active polygonal fault system suggest upward fluid migration and fluid and sediment expulsion at the seafloor through a probable mud volcano and other piercement structures. One large debris flow deposit, named Formentera Debris Flow, has been identified on the lower slope and rise of the south Formentera margin. Based on current observations, we hypothesize that the landslide originating the Formentera Debris Flow occurred in the Holocene, perhaps in historical times.

Angelo CamerlenghiEmail:

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Phytoplankton Functional Groups in a Tropical Estuary: Hydrological Control and Nutrient Limitation   总被引：3，自引：0，他引：3  

L. S. Costa  V. L. M. Huszar  A. R. Ovalle 《Estuaries and Coasts》2009,32(3):508-521

Hydrology and nutrients have been indicated as the main driving factors acting on phytoplankton biomass and composition in estuarine systems, although grazing may occasionally have some influence. In order to identify these factors over temporal and spatial scales, we analyzed physical, chemical, and biological properties of a tropical river-dominated estuary during the dry and rainy seasons. As far as we know, this is the first time that the functional groups approach has been used to analyze the changes in phytoplankton composition in an estuary. This recent framework is based on the tolerances and sensitivities in relation to environmental conditions of groups of species, which are labeled by alpha-numeric codes (Reynolds et al., J. Pl. Res. 24:417–428, 2002). In the estuary of Paraíba do Sul River, all phytoplankton groups were represented by freshwater organisms, indicating the strong influence of the river. However, remarkable shifts in composition and biomass occurred from the low to high flushing seasons, due much more to the river discharge than to nutrient availability. The overall results showed no nitrogen, phosphorus, or silica limitation to phytoplankton growth (mean values: dissolved inorganic nitrogen?=?30.5 µM, soluble reactive phosphorus?=?1.45 µM, and silica?=?208.05 µM). The higher river flow supports a lower phytoplankton biomass composed mainly of nanoplankton (<20 µm) fast-growing functional groups, which are able to maintain biomass even in high flushing conditions (X₁), or large heavy organisms, such as some heavy diatoms of group P, which are able to be in suspension in shallow and turbulent systems. The lower river flow led to the coexistence of large organisms (>20 µm) of the groups P and F, which include slow-growing populations typically found in mesotrophic lakes. Although the functional group approach was originally developed for temperate lakes, our data support this approach for a tropical estuarine environment.  相似文献