The Influence of Path Corrections and a Three-dimensional Global <Emphasis Type="Italic">P</Emphasis>-wave Velocity Model on Seismic Event Location in Kazakhstan     

Renate?Hartog  Wim?Spakman  Clifford H.?ThurberEmail author  Chad?Trabant 《Pure and Applied Geophysics》2003,160(12):2239-2255

We relocate 81 large nuclear explosions that were detonated at the Balapan and Degelen Mountain subregions of the Semipalatinsk test site in Kazakhstan during the years 1978 to 1989. The absolute locations of these explosions are available, as well as very accurate estimates of their origin times. This ground truth information allows us to perform a detailed analysis of location capability. We use a sparse network of stations with highly accurate first arrival picks measured using a waveform cross-correlation method. These high quality data facilitate very accurate location estimates with only a few phases per event. We contrast two different approaches: 1) a calibration-based approach, where we achieve improved locations by using path corrections, and 2) a model-based approach, where we achieve improved locations by relocating in a recently published global 3-D P-velocity model. Both methods result in large improvements in accuracy of the obtained absolute locations, compared to locations obtained in a 1-D reference earth model (ak135). The calibration-based approach gives superior results for this test site, in particular when arrival times from regional stations are included. Estimated locations remain well within a 1000 km² region surrounding the ground truth locations when the path corrections for the Balapan and Degelen Mountain subregions are interchanged, but even for the short separation between these two regions, we find variations in the path corrections that cause systematic mislocations. The model-based approach also results in substantially reduced mislocation distances and has the distinct advantage that it is, in principle, transportable to other source regions around the world.  相似文献   

Classifications of retail stores and shopping centres: some methodological issues     

Clifford M. Guy 《GeoJournal》1998,45(4):255-264

This paper reviews current methods used in classifying retail outlets and areas devoted to retailing, in the geographical and town planning literature. For retail outlets, classifications based upon types of goods sold, and types of shopping trip, are discussed. This is followed by an analysis of modern large store development which reflects property developers' and retailers' concerns. Areas devoted to retail uses are subdivided into unplanned ‘retail areas’ and planned ‘shopping centres’. Traditional classifications based upon central place theory are reviewed for both of these types, and found wanting in the light of recent changes in retail development practice and consumer behaviour. Classifications based upon physical development characteristics and type of shopping trip are recommended. Finally, classifications of urban retail location are examined. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Editors’ message     

Clifford I. Voss  William E. Wilson 《Hydrogeology Journal》1996,4(2):2-2

  相似文献   

Editors’ message     

Clifford I. Voss  William E. Wilson 《Hydrogeology Journal》1996,4(1):2-2

  相似文献   

Modelling of near-surface seismic structure beneath Hawaii using reverberations     

Yingping Li  Clifford H. Thurber 《Geophysical Journal International》1995,122(2):441-456

  相似文献   

The size frequency and abundance of subtidal bloodworms (Glycera dibranchiata,ehlers) in Montsweag Bay,Woolwich-Wiscasset,Maine     

Edwin P. Creaser  David A. Clifford 《Estuaries and Coasts》1986,9(3):200-207

A study was conducted in the subtidal portion of Montsweag Bay (Woolwich-Wiscasset, Maine) between the mean low water mark and 1.5 m depth, to determine the size composition, abundance, and monetary value of bloodworms (Glycera dibranchiata). Eight 1-m² subplots were sampled in each of three regions of equal size with the aid of a compressed air lift apparatus. Bloodworms collected varied in length between 1 and 31 cm; the majority were smaller than commercial size (<12 cm). A mean length of 4.6±0.03 cm (95% confidence level) was reported for noncommercial size worms and 19.6±2.0 cm, (95% confidence level) for commercial worms. Although the numbers of bloodworms of all sizes collected in region 1 were significantly greater than the numbers collected from region 3, no significant differences among the numbers of commercial-sized bloodworms were found in subplots within the three regions. Estimates of the standing crop and value of commercial bloodworms present were derived from overall estimates of the numbers m^?2 and the standard error at 95% confidence (1.04±0.58 worms), the subtidal area, and the 1971 and 1983 value of commercial worms. During 1971, the 6,059,040±3,379,080 commercial-sized bloodworms present were valued at $242,362.00±$135,163.00. At 1983 prices, the value of these worms would be from $363,542.00±$202,745.00 to $605,904.00±$337,908.00. Construction of a causeway, which created subtidal conditions where intertidal conditions formerly existed, apparently had no adverse effect upon the bloodworm population present.  相似文献   

Temporal patterns of feeding by blue crabs (Callinectes sapidus) in a tidal-marsh creek and adjacent seagrass meadow in the lower Chesapeake Bay     

Clifford H. Ryer 《Estuaries and Coasts》1987,10(2):136-140

A 24-h study of blue crab feeding periodicity was conducted concurrently in a tidal marsh creek and adjacent seagrass meadow in the lower Chesapeake Bay. Crabs from the grassbed tended to have fuller guts than crabs from the marsh creek. In the grassbed, a weak trend toward nocturnal feeding was observed, with an apparent peak at dusk. During the day, crabs were not easily observed and were assumed to be feeding beneath the eelgrass canopy; at night crabs fed in the canopy. In the marsh creek, feeding was related to the tidal cycle, with guts being fullest at high tide and decreasing to lows just prior to the next high tide. This study suggests the potential importance of habitat on blue crab feeding patterns.  相似文献   

Effect of finite sampling on atmospheric spectra   总被引：2，自引：0，他引：2  

J. C. Kaimal  S. F. Clifford  R. J. Lataitis 《Boundary-Layer Meteorology》1989,47(1-4):337-347

The effect of a finite averaging time on variances is well known, but its effect on power spectra is less clearly understood. We present numerical solutions for the spectral distortion arising from sampling over a finite time interval T and show that the commonly used filter function (1 – sinc²f T), valid for variances, is a reasonable approximation for power spectra only when T 10 _m , where f is the cyclic frequency, and _m is the dominant time scale of the process. Our results exhibit an increasingly steeper low-frequency roll-off as T decreases relative to _m , indicating that the measured spectrum is subject to a greater suppression of the lower frequencies (f > 1/T) than predicted by (1 – sinc²f T). This suppression is, in a sense, compensated by an overestimation of spectral estimates in the frequency range f 1/T.  相似文献   

The relationship between earthquake swarms and magma transport: Kilauea volcano,Hawaii     

Timothy L. Karpin  Clifford H. Thurber 《Pure and Applied Geophysics》1987,125(6):971-991

A detailed investigation of earthquake locations and focal mechanisms for swarms associated with intrusive events at Kilauea volcano, Hawaii, further illuminates the relationships among stress state, faulting, and magma transport. We determine the earthquake locations and mechanisms using a three-dimensional crustal model to improve their accuracy and consistency. Swarms in Kilauea's upper east and southwest rift zones, from the years 1980 through 1982, provide clear evidence for the propagation and/or dilation of dikes. Focal mechanisms are predominantly strike-slip, and the faulting and inferred dike orientations can be interpreted quite consistently in terms of the model ofHill (1977). Stresses induced by the summit magma reservoir system strongly control faulting and magma transport in the rift zones close to the summit.  相似文献   

Gases and trace elements in soils at the North Silver Bell deposit, Pima County, Arizona     

Margaret E. Hinkle  Clifford A. Dilbert 《Journal of Geochemical Exploration》1984,20(3):323-336

Soil samples were collected over the North Silver Bell porphyry copper deposit near Tucson, Arizona. Volatile elements and compounds in gases derived from the soils and metallic elements in the soils were analyzed in order: (1) to see which volatile constituents of the soils might be indicative of the ore body or the alteration zones; and (2) to distinguish the ore and alteration zones by comparison of trace elements in the soil.Plots of analytical data on trace elements in soils indicated a typical distribution pattern for metals around a porphyry copper deposit, with copper, molybdenum, and arsenic concentrations higher over the ore body, and zinc, lead, and silver concentrations higher over the alteration zones.Higher than average concentrations of helium, carbon disulfide, and sulfur dioxide adsorbed on soils were found over the ore body, whereas higher concentrations of carbon dioxide and carbonyl sulfide were found over the alteration zones.  相似文献