First-principles-based calculations of the CaCO<Subscript>3</Subscript>–MgCO<Subscript>3</Subscript> and CdCO<Subscript>3</Subscript>–MgCO<Subscript>3</Subscript> subsolidus phase diagrams     

B. P. Burton  A. Van de Walle 《Physics and Chemistry of Minerals》2003,30(2):88-97

 Planewave pseudopotential calculations of supercell total energies were used as bases for first-principles calculations of the CaCO₃–MgCO₃ and CdCO₃–MgCO₃ phase diagrams. Calculated phase diagrams are in qualitative to semiquantitative agreement with experiment. Two unobserved phases, Cd₃Mg (CO₃)₄ and CdMg₃(CO₃)₄, are predicted. No new phases are predicted in the CaCO₃–MgCO₃ system, but a low-lying metastable Ca₃Mg(CO₃)₄ state, analogous to the Cd₃Mg(CO₃)₄ phase is predicted. All of the predicted lowest-lying metastable states, except for huntite CaMg₃(CO₃)₄, have dolomite-related structures, i.e. they are layer structures in which A _m B _n cation layers lie perpendicular to the rhombohedral [111] vector. Received: 6 May 2002 / Accepted: 23 October 2002 Acknowledgements This work was partially supported by NSF contract DMR-0080766 and NIST.  相似文献   

Field variability of landslide model parameters   总被引：5，自引：1，他引：4  

A. Burton  T. J. Arkell  J. C. Bathurst 《Environmental Geology》1998,35(2-3):100-114

 A data set of parameters (slope, soil depth and soil shear strength) relevant to spatially distributed modelling of shallow landslides triggered by rain and snowmelt events was determined from field measurements in 250 grid elements of dimensions 25 m (downslope)×10 m (across slope) in an area of 250 m×250 m on a hillslope in Scotland. These data provide an unusually detailed basis for the evaluation of spatial variability and uncertainty in model parameterisation. The variations in slope and soil strength are represented adequately by normal distributions; a Weibull distribution is suggested for the soil depth data. The factor of safety calculated at each point in the grid was shown partially to identify observed landslides, with a number of false predictions of occurrence. Trend analysis and semivariogram analysis of the data set suggest that the use of kriging could improve upon this approach to landslide prediction by providing areal estimates of parameters at the grid element scale with associated error bounds. Received: 30 October 1996 · Accepted: 25 June 1997  相似文献   

The Source Mechanism of the Athens Earthquake,September 7, 1999, Estimated from P Seismograms Recorded at Long Range     

Sargeant  S.L.  Burton  P.W.  Douglas  A.  Evans  J.R. 《Natural Hazards》2002,27(1-2):35-45

On 7 September, 1999, an earthquake (5.8 m_b ^USGS)took place about 20 km from the centre of Athens, until then a seismically quiet region ofeastern Greece. Considerable damage ranging from rock falls to the collapse of reinforcedconcrete structures was reported in the city and surrounding area. No surface break which couldbe directly attributed to rupture on the fault plane was mapped. We use the relativeamplitude method and forward modelling of broadband P seismogramsrecorded at long range to produce a two-dimensional model of the source. We conclude that the earthquake tookplace on a south-west dipping normal fault at a depth of 10 km. This implies that the depthof the seismogenic zone in the area is comparable to other more active regions of Greece.The rupture speed (2.1 km/s) and stress drop (0.54 MPa) are low and are typical of earthquakesin a tectonic environment dominated by high rates of extension. The estimated seismicmoment is 6.014 × 10¹⁷ N m. We have investigated reported rupture directivity and thepossibility of a circular rupture is also examined. Extrapolation of the fault plane to the freesurface suggests that the earthquake took place on a structure associated with the Fili fault.  相似文献   

An approach to the classification of Utah mine spoils and tailings based on surface hydrology and erosion     

Timothy A. Burton  Gerald F. Gifford  George E. Hart 《Environmental Geology》1978,2(5):269-278

The physical similarities among mine spoils may be strongly influenced by the geologic source of the spoils where overburden is produced from areas of simple geologic structure. Textures and bulk densities are influenced by the methods of handling the materials during mining and disposal operations. Where these influences are the same in more than one mining site, surface hydrology and erosion parameters are often similar. A specific tailing deposit may be highly variable with respect to the physical and chemical characteristics produced by methods of ore treatment and concentration. This variability makes it difficult to classify tailings based on surface hydrology and erosion. Hydrologic characteristics of spoil deposits as related to future successful rehabilitation may be improved by (1) conducting mining activities to permit identification and segregation of favorable overburden strata for use in revegetation, (2) reconstituting soil for optimum plant growth, (3) shaping spoils to be compatible with surrounding topography, (4) mulching with organic materials, and (5) avoiding or ameliorating compaction of the soil-spoil surface. Mr. Burton is currently hydrologist with the Bureau of Land Management in Lewiston, Montana, U.S.A.  相似文献   

An evaluation of seismic hazard parameters in southern Turkey     

A. Yilmaztürk  P. W. Burton 《Journal of Seismology》1999,3(1):61-81

To investigate the characteristics of earthquake hazard parameters as a means of identifying different zones of seismicity, we have compiled a catalogue of about 1850 moderate to large-sized earthquakes with magnitudes m4.0 or greater in southern Turkey for the time period from 1900 to 1990. Several methods have been applied to the earthquake catalogue to assess seismic hazard. The study area is divided into 77 overlapping cells of 2° size. Theoretical calculations were made for the prediction of maximum magnitude, intensity, b-values, strain energy release and corresponding m3 and peak ground acceleration levels for a given period of time. The resultant seismic hazard for each parameter is depicted as a contour map to indicate lateral variations in areas of seismic source. A combination and evaluation of various hazard parameters resulted in more reasonable estimates of hazard. It is found that the most hazardous seismic zones are the Rhodes and Burdur zones where the level of peak ground acceleration reaches up to 280 cm s-2 for an average return period of 100 years.  相似文献   

Coseismic crustal deformation on a fault zone defined by microseismicity in the Pavliani area, central Greece   总被引：1，自引：0，他引：1  

Paul W. Burton  Nikolaos S. Melis†  Mike Brooks 《Geophysical Journal International》1995,123(1):16-40

  相似文献   

Seismicity in the Hellenic Volcanic Arc: relation between seismic parameters and the geophysical fields in the region   总被引：2，自引：0，他引：2  

Theodoros M. Tsapanos  Dimitrios Galanopoulos  Paul W. Burton 《Geophysical Journal International》1994,117(3):677-694

  相似文献   

Regional slaty cleavage formation and fold axis rotation by re-use and reactivation of pre-existing foliations: the Fiery Creek Slate Belt, North Queensland     

Brett K. Davis  Aidan Forde 《Tectonophysics》1994,230(3-4):161-179

A deformation history, comprised of six separate deformation events of differing intensity, has affected the rocks of the South Palmer River region of the the Hodgkinson Province, north Queensland. Within this region, a zone of pervasive slaty cleavage, herein termed the Fiery Creek Slate Belt, has developed as a result of the superposition of fabrics formed during several of these events. The most important processes in the formation of this composite cleavage were the re-use and reactivation of the favourably oriented, steep, N-S-trending S₂ foliation by the intense fourth deformation event, D₄. This produced micro-, meso- and macroscopic folds in an originally shallow S₃ foliation, produced during the intervening D₃ deformation, with an axial planar S₂–S₄ foliation. The D₄ stretching lineation, L⁴₄, plunges subvertically to steeply north and indicates that shear during D₄ was oriented steeply north-south. In the Fiery Creek Slate Belt, D₂ fold axes are interpreted to have formed in much shallower orientations than their present moderately N-S-plunging to subvertical orientations. We consider this to be a result of D₄ shear, which caused variable degrees of rotation of D₂ fold axes toward the D₄ stretching lineation due to subparallelism of the bulk shortening directions of the D₂ and D₄ events. Near-total destruction of the pre-D₄ foliations during slaty cleavage formation has produced a misleading impression of a simple deformation history. There is no relationship between metamorphic grade and intensity of slaty cleavage development.  相似文献   

The Behaviour of Dissolved Silicon During Estuarine Mixing I. Investigations in Southampton Water     

Burton  J. D.; Liss  P. S.; Venugopalan  V. K. 《ICES Journal of Marine Science》1970,33(2):134-140

  相似文献   

冰穹C的大气条件:天文含意     

J.S. Lawrence　M.C.B. Ashley　M.G. Burton　J.W.V. Storey 《天文学报》2007,48(1):48-53

在南极洲高原的冰穹C有望发现非凡的天文观测条件,受此鼓舞,许多国际小组协同努力对该地的大气条件作全面的测量．评述对冰穹C的选址现况,讨论过去、现在和计划中的选址仪器,迄今已得到的结果,以及这些结果的天文含意．  相似文献