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This paper demonstrates the utility, in an applied context, of a standard Teitz and Bart heuristic for solving location-allocation problems. The example discussed is the location of veterinary clinics in Wellington, New Zealand. A distinct ‘service-poor’ area is identified in southern Wellington suggesting that the existing system of clinics, especially the largest multi-veterinary practice, is vulnerable to intrusion by competitors. A variety of strategies, involving new clinics and clinic relocation are analysed to ascertain alternative courses of action for both existing clinic operators and competitors. The appropriateness of this type of analysis as an aid to decision-making is reflected in the locational response of one practice to protect its share of the market for veterinary services. 相似文献
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Christopher Kissling 《GeoJournal》1993,29(3):291-297
International civil aviation is circumscribed by a plethora of bilateral air service agreements between sovereign nations. In recent years there has been a marked trend to liberalise these agreements as well as moves to create multilateral common markets as appear to be emerging in Europe. Airline managements are being given opportunities to implement operational strategies once severely proscribed in confidential memoranda of understanding lying behind the public bilateral documents. In keeping with the philosophy of extending the Closer Economic Relations (CER) agreement, Australia and New Zealand have been exploring the ramifications of bringing trade in air services within the ambit of CER. This paper examines some of the factors affecting the trans Tasman civil aviation environment and discusses the implications of modifications to air services in and between Australia and New Zealand. 相似文献
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Accurate hypocentre determination in the seismogenic zone of the subducting Nazca Plate in northern Chile using a combined on-/offshore network 总被引:5,自引:0,他引:5
The coupled plate interface of subduction zones—commonly called the seismogenic zone—has been recognized as the origin of fatal earthquakes. A subset of the after-shock series of the great Antofagasta thrust-type event (1995 July 30; M w = 8.0) has been used to study the extent of the seismogenic zone in northern Chile. To achieve reliable and precise hypocentre locations we applied the concept of the minimum 1-D model, which incorporates iterative simultaneous inversion of velocity and hypocentre parameters. The minimum 1-D model is complemented by station corrections which are influenced by near-surface velocity heterogeneity and by the individual station elevations. By relocating mine blasts, which were not included in the inversion, we obtain absolute location errors of 1 km in epicentre and 2 km in focal depth. A study of the resolution parameters ALE and DSPR documents the importance of offshore stations on location accuracy for offshore events. Based on precisely determined hypo-centres we calculate a depth of 46 km for the lower limit of the seismogenic zone, which is in good agreement with previous studies for this area. For the upper limit we found a depth of 20 km. Our results of an aseismic zone between the upper limit of the seismogenic zone and the surface correlates with a detachment zone proposed by other studies; the results are also in agreement with thermal studies for the Antofagasta forearc region. 相似文献
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A series of 112 earthquakes was recorded between October 2005 and August 2007 during the excavation of the MFS Faido, the southernmost access point of the new Gotthard Base Tunnel. Earthquakes were recorded at a dense network of 11 stations, including 2 stations in the tunnel. Local magnitudes computed from Wood?CAnderson-filtered horizontal component seismograms ranged from ?1.0 to 2.4; the largest earthquake was strongly felt at the surface and caused considerable damage in the tunnel. Hypocenter locations obtained routinely using a regional 3-D P-wave velocity model and a constant Vp/Vs ratio 1.71 were about 2?km below the tunnel. The use of seismic velocities calibrated from a shot in the tunnel revealed that routinely obtained hypocenter locations were systematically biased to greater depth and are now relocated to be on the tunnel level. Relocation of the shot using these calibrated velocities yields a location accuracy of 25?m in longitude, 70?m in latitude, and 250?m in focal depth. Double-difference relative relocations of two clusters with highly similar waveforms showed a NW?CSE striking trend that is consistent with the strike of mapped faults in the MFS Faido. Source dimensions computed using the quasidynamic model of Madariaga (Bull Seismo Soc Am 66(3):639?C666, 1976) range from 50 to 170?m. Overlapping source dimensions for earthquakes within the two main clusters suggests that the same fault patch was ruptured repeatedly. The observed seismicity was likely caused by stress redistribution due to the excavation work in the MFS Faido. 相似文献
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I. V. Nizkous I. A. Sanina E. Kissling L. I. Gontovaya 《Izvestiya Physics of the Solid Earth》2006,42(4):286-296
Arrival times of P and S waves from local earthquakes in the Kamchatka area of the Kurile-Kamchatka Island Arc are used for calculating a spatial model of the elastic wave velocity distribution to a depth of 200 km. The lithosphere is shown to be strongly stratified in its velocity properties and laterally heterogeneous within the mantle wedge and seismic focal zone. A lower velocity layer (an asthenospheric wedge) is identified at depths of 70–130 km beneath the Eastern Kamchatka volcanic belt. The morphology of the Moho interface and the velocity properties of the crust are studied. The main tectonic structures of the region are shown to be closely interrelated with deep velocity heterogeneities. Regular patterns in the statistics of the earthquakes are analyzed in relation to variations in the elastic wave velocities in the focal layer. A mechanism of lithospheric block displacements along weakened zones of the lower crust and upper mantle is proposed. 相似文献
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Kamil Ustaszewski Stefan M. Schmid Bernhard Fügenschuh Matthias Tischler Eduard Kissling Wim Spakman 《Swiss Journal of Geoscience》2008,101(1):273-294
A map-view palinspastic restoration of tectonic units in the Alps, Carpathians and Dinarides reveals the plate tectonic configuration before the onset of Miocene to recent deformations. Estimates of shortening and extension from the entire orogenic system allow for a semi-quantitative restoration of translations and rotations of tectonic units during the last 20 Ma. Our restoration yielded the following results: (1) The Balaton Fault and its eastern extension along the northern margin of the Mid-Hungarian Fault Zone align with the Periadriatic Fault, a geometry that allows for the eastward lateral extrusion of the Alpine-Carpathian-Pannonian (ALCAPA) Mega-Unit. The Mid-Hungarian Fault Zone accommodated simultaneous strike-perpendicular shortening and strike-slip movements, concomitant with strike-parallel extension. (2) The Mid-Hungarian Fault Zone is also the locus of a former plate boundary transforming opposed subduction polarities between Alps (including Western Carpathians) and Dinarides. (3) The ALCAPA Mega-Unit was affected by 290 km extension and fits into an area W of present-day Budapest in its restored position, while the Tisza-Dacia Mega-Unit was affected by up to 180 km extension during its emplacement into the Carpathian embayment. (4) The external Dinarides experienced Neogene shortening of over 200 km in the south, contemporaneous with dextral wrench movements in the internal Dinarides and the easterly adjacent Carpatho-Balkan orogen. (5) N–S convergence between the European and Adriatic plates amounts to some 200 km at a longitude of 14° E, in line with post-20 Ma subduction of Adriatic lithosphere underneath the Eastern Alps, corroborating the discussion of results based on high-resolution teleseismic tomography.The displacement of the Adriatic Plate indenter led to a change in subduction polarity along a transect through the easternmost Alps and to substantial Neogene shortening in the eastern Southern Alps and external Dinarides. While we confirm that slab-pull and rollback of oceanic lithosphere subducted beneath the Carpathians triggered back-arc extension in the Pannonian Basin and much of the concomitant folding and thrusting in the Carpathians, we propose that the rotational displacement of this indenter provided a second important driving force for the severe Neogene modifications of the Alpine-Carpathian-Dinaridic orogenic system. 相似文献
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Local and regional minimum 1D models for earthquake location and data quality assessment in complex tectonic regions: application to Switzerland 总被引:1,自引:0,他引:1
One-dimensional (1D) velocity models are still widely used for computing earthquake locations at seismological centers or
in regions where three-dimensional (3D) velocity models are not available due to the lack of data of sufficiently high quality.
The concept of the minimum 1D model with appropriate station corrections provides a framework to compute initial hypocenter
locations and seismic velocities for local earthquake tomography. Since a minimum 1D model represents a solution to the coupled
hypocenter-velocity problem it also represents a suitable velocity model for earthquake location and data quality assessment,
such as evaluating the consistency in assigning pre-defined weighting classes and average picking error. Nevertheless, the
use of a simple 1D velocity structure in combination with station delays raises the question of how appropriate the minimum
1D model concept is when applied to complex tectonic regions with significant three-dimensional (3D) variations in seismic
velocities. In this study we compute one regional minimum 1D model and three local minimum 1D models for selected subregions
of the Swiss Alpine region, which exhibits a strongly varying Moho topography. We compare the regional and local minimum 1D
models in terms of earthquake locations and data quality assessment to measure their performance. Our results show that the
local minimum 1D models provide more realistic hypocenter locations and better data fits than a single model for the Alpine
region. We attribute this to the fact that in a local minimum 1D model local and regional effects of the velocity structure
can be better separated. Consequently, in tectonically complex regions, minimum 1D models should be computed in sub-regions
defined by similar structure, if they are used for earthquake location and data quality assessment. 相似文献