An envelope for Mohr's circle in seismically excited three‐dimensional structures     

Charles Menun 《地震工程与结构动力学》2004,33(9):981-998

A previously developed response‐spectrum‐based procedure for computing the envelope that bounds the time‐varying realizations of Mohr's circle at any prescribed location within a two‐dimensional structure is extended for use with three‐dimensional structures subjected to as many as three translational components of ground acceleration. The proposed envelope, which is completely defined by quantities that are routinely used and calculated in conventional response spectrum analyses, is developed for the general case in which the principal directions of the earthquake, along which the ground accelerations are uncorrelated, are unknown. The accuracy of the proposed envelope is evaluated by comparing it to the results of an ensemble of time‐history analyses performed on a concrete arch dam using simulated accelerograms. It is found that the proposed envelope has a level of accuracy that is suitable for structural design and analysis. The largest observed difference between the simulated and predicted mean envelopes is less than 5%. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

May 2004     

J. C. Green  Charles H. Shaw 《Environmental Geology》2004,45(7):1036-1038

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Preliminary Method Development and Evaluation of a Statewide Assessment of Ground Water and Surface Water Interactions     

Richard C. Berg  Donald A. Keefer  Misganaw Demissie  Ganapathi Ramamurthy  Charles A. Job 《Ground Water Monitoring & Remediation》1997,17(3):64-69

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Generation of the teleseismic P-wave coda from Aleutian earthquakes     

Charles H. Estabrook  Michael Weber  Rainer Kind 《Geophysical Journal International》1997,130(2):349-364

We investigate large-amplitude phases arriving in the P -wave coda of broad-band seismograms from teleseisms recorded by the Gräfenberg array, the German Regional Seismic Network and the Global Seismic Network. The data set consists of all events m _b≤ 5.6 from the Aleutian arc between 1977 and 1992. Earthquakes with large-amplitude coda waves correlate with the presence of oceanic crust in the source region. The amplitudes sometimes approach those of the P wave, much larger than predicted by theory. Modelling indicates that phases in the P -wave coda cannot be P -wave multiples beneath the source and receiver, or underside reflections, which precede PP , from upper-mantle discontinuities. Among the events, seismograms are very similar, where the arrival times of the unusual phases agree approximately with the predicted times of S -to- P conversions from the upper-mantle discontinuities under the source. Because the large-amplitude phases in the P -wave coda have little, if any, dependence on event depth and have predominantly an SV -wave radiation pattern towards the receiver, we suggest that they originate as SV and/or Rayleigh waves and are enhanced by lateral heterogeneity and multipathing from the subducting Aleutian slab.  相似文献   

Scale Dependency of Hydraulic Conductivity Measurements   总被引：8，自引：0，他引：8  

Charles W. Rovey II  Douglas S. Cherkauer 《Ground water》1995,33(5):769-780

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Periglacial geomorphology edited by J. C. Dixon and A. D. Abrahams,Binghamton Symposia,No 22, John Wiley and Sons,Chichester, 1992. No. of pages: xiii + 354. Price: £60.00. ISBN 0-471-93342-2     

Charles Harris 《地球表面变化过程与地形》1993,18(5):470-470

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An evaluation of the global variations in the major element chemistry of arc basalts   总被引：2，自引：0，他引：2  

Terry Plank  Charles H. Langmuir 《Earth and Planetary Science Letters》1988,90(4):349-370

Arc volcanoes occur at convergent margins with a wide range in subduction parameters, and variations in these parameters might be expected to lead to variations in the chemistry of magmas parental to arcs. Major element analyses from approximately 100 volcanic centers within 30 arcs, normalized to 6% MgO to minimize the effects of crystal fractionation, display wide variations. Na₂O and CaO at 6% MgO (Na_6.0 and Ca_6.0) correlate remarkably well with the thickness of the overlying crust. These systematics are consistent with two possible models. In the first model, the crust behaves as a chemical filter; where the crust is thick, magmas crystallize at higher pressure and interact more extensively with the arc crust. Modeling of high-pressure crystallization and assimilation, however, does not reproduce the associated variations in Na_6.0 and Ca_6.0 without calling upon complicated combinations of fractionating phases and assimilants. In the second model, crustal thickness determines the height of the mantle column available for melting beneath arc volcanoes. If melting begins beneath arcs at similar depths, then the column of mantle that undergoes decompression melting is much shorter beneath the thickest arc crust. The shorter mantle column for arcs built on thick crust will lead to smaller extents of melting in the mantle, and hence higher Na_6.0 and lower Ca_6.0 in the parental magmas. Modeling shows that variations in the extent of melting in the mantle can easily account for the associated variations in Ca_6.0 and Na_6.0. The abundances of the other major elements at 6% MgO do not correlate well with crustal thickness, or any other subduction parameter. Co-variation of some of these other major elements (e.g., Si_6.0 and Fe_6.0) within individual arcs suggests that they are strongly influenced by local crustal level processes that obscure partial melting systematics. Correction for the crustal processes improves the relationship between Na_6.0 and Ca_6.0 that is so readily explained by partial melting. The extents of melting in the mantle beneath arc volcanoes estimated from the ranges in Na_6.0 and Ca_6.0 are remarkably similar to those estimated beneath mid-ocean ridges. This observation provides further evidence that the mantle wedge, and not the slab, melts beneath arc volcanic fronts.  相似文献   

Cosolvent Influences on Organic Solute Retardation Factors     

Charles A. Staples  Stephanie J. Geiselmann 《Ground water》1988,26(2):192-198

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Radon Distribution in Domestic Water of Texas   总被引：1，自引：0，他引：1  

Irina Cech  Charles Kreitler  Howard Prichard  Alfonso Holguin  Mengistu Lemma 《Ground water》1988,26(5):561-569

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DISCUSSION OF PAPERS     

Charles B. Davis 《Ground water》1988,26(5):649-650

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