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Tuna Eken Z. Hossein Shomali Roland Roberts Reynir Bödvarsson 《Geophysical Journal International》2007,169(2):617-630
Upper-mantle structure under the Baltic Shield is studied using non-linear high resolution teleseismic P -phase tomography. Observed relative arrival-time residuals from 52 teleseismic earthquakes recorded by the Swedish National Seismological Network (SNSN) are inverted to delineate the structure of the upper mantle. The network consists of 47 (currently working) three-component broad-band stations located in an area about 450 km wide and 1450 km long. In order to reduce complications due to possible significant three-dimensionality of Earth structure, events chosen for this study lay close to in-line with the long-axis of the array (±30°) . Results indicate P -wave velocity perturbations of ±3 per cent down to at least 470 km below the network. The size of the array allows inversion for structures even at greater depths, and lateral variations of velocity at depths of up to 680 km appear to be resolved. Below the central part of the array (60°–64° N), where ray coverage is best, the data reveals a large region of relatively low velocity at depths of over about 300 km. At depths less than about 250–300 km, the models include a number of features, including an apparent slab-like structure dipping gently towards the north. 相似文献
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Comprehensive risk assessments are fundamental to effective emergency management. These assessments need to identify the range
of hazards (or perils) an entity is exposed to and quantify the specific threats associated with each of those hazards. While
hazard identification is commonly, if not formally, conducted in most circumstances, specific threat analysis is often overlooked
for a variety of reasons, one of which is poor communication with subject matter experts. This poor communication is often
attributable to an adherence to scientific jargon and missed opportunities to simplify information. In Canada, for example,
earthquake hazard calculations have been readily available to engineers and scientists for decades. This hazard information,
however, is expressed in terms of peak ground accelerations (PGA) or spectral accelerations (SA) that are foreign concepts
to most emergency managers, community decision-makers and the public-at-large. There is, therefore, a need to more clearly,
simply and effectively express seismic hazard information to the non-scientific community. This paper provides crustal, sub-crustal
and subduction interface earthquake shaking probabilities, expressed as simple percentages for each of 57 locations across
Vancouver Island, British Columbia, Canada. Calculations present the likelihood of earthquake shaking on Vancouver Island
as the probabilities of exceeding each of three shaking intensity thresholds (“widely felt”; onset of “non-structurally damaging”
shaking; and onset of “structurally damaging” shaking) over four timeframes (10, 25, 50 and 100 years). Results are based
on the latest Geological Survey of Canada hazard models used for the 2010 national building code and are presented in both
tabular and graphic formats. This simplified earthquake hazard information is offered to aid local residents, organizations
and governments in understanding and assessing their risk and to encourage and facilitate sound earthquake preparedness funding
decisions. 相似文献
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Tuna Tasan 《GeoJournal》1999,49(1):91-103
The aim of this paper is to show how and in what sense the post-socialist transformation process has influenced the urban
spatial structure of Warsaw with the help of empirical evidence dealing with housing. Therefore, the main focus of the study
is the transformation of the housing market in the 1990s under social and economic restructuring process. The article comprises
two parts: the first part involves the geographical development of the urban spatial structure within the context of housing
market changes. In order to explain today's transformation, the system of socialist time is also discussed. In the second
part emphasis is placed on the evidence of the transformation in urban space, dealing with new tendencies and challenging
mechanisms in the housing market. The last period of transformation is also investigated in terms of changes in the urban
space since housing is seen as an important factor of urban transformation. Hence, following the brief outline of historical
development of the urban space housing market changes including the privatization of urban land is going to be the concern
of the paper. The problems of the transformation and practical implementation of the privatization process are also discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Tuna Eken Jaroslava Plomerová Roland Roberts Ludek Vecsey Vladislav Babuška Hossein Shomali Reynir Bodvarsson 《Tectonophysics》2010,480(1-4):241-258
Body-wave analysis — shear-wave splitting and P travel time residuals — detect anisotropic structure of the upper mantle beneath the Swedish part of Fennoscandia. Geographic variations of both the splitting measurements and the P-residual spheres map regions of different fabrics of the mantle lithosphere. The fabric of individual mantle domains is internally consistent, usually with sudden changes at their boundaries. Distinct backazimuth dependence of SKS splitting excludes single-layer anisotropy models with horizontal symmetry axes for the whole region. Based upon joint inversion of body-wave anisotropic parameters, we instead propose 3D self-consistent anisotropic models of well-defined mantle lithosphere domains with differently oriented fabrics approximated by hexagonal aggregates with plunging symmetry axes. The domain-like structure of the Precambrian mantle lithosphere, most probably retaining fossil fabric since the domains' origin, supports the idea of the existence of an early form of plate tectonics during the formation of continental cratons already in the Archean. Similarly to different geochemical and geological constraints, the 3D anisotropy modelling and mapping of fabrics of the lithosphere domains contribute to tracking plate tectonics regimes back in time. 相似文献
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Hiroaki Yamanaka Ögur Tuna Özmen Kosuke Chimoto Mehmet Akif Alkan Muammer Tün Emrah Pekkan Oguz Özel Derya Polat Murat Nurlu 《Journal of Seismology》2018,22(5):1127-1137
We have explored 1D S-wave velocity profiles of shallow and deep soil layers over a basement at strong motion stations in Eskisehir Province, Turkey. Microtremor array explorations were conducted at eight strong motion stations in the area to know shallow 1D S-wave velocity models. Rayleigh wave phase velocity at a frequency range from 3 to 30 Hz was estimated with the spatial autocorrelation analysis of array records of vertical microtremors at each station. Individual phase velocity was inverted to a shallow S-wave velocity profile. Low-velocity layers were identified at the stations in the basin. Site amplification factors from S-wave parts of earthquake records that had been estimated at the strong motion stations by Yamanaka et al. (2017) were inverted to the S-wave velocities and Q-values of the sedimentary layers. The depths to the basement with an S-wave velocity of 2.2 km/s are about 1 km in the central part of the basin, while the basement becomes shallow as 0.3 km in the marginal part of the basin. We finally discussed the effects of the shallow and deep sedimentary layers on the 1D S-wave amplification characteristics using the revealed profiles. It is found that the shallow soil layers have no significant effects in the amplification at a frequency range lower than 3 Hz in the area. 相似文献
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This paper investigates the equity implications of marketing ecosystem services in protected areas and rural communities. We use a three-tiered equity framework to analyse four distinct efforts to commercialise watershed recharge and carbon dioxide fixation by forests in Meso-America. We show that project development and participation are strongly mediated by organisational networks, as well as existing rights of access over land and forest resources. We demonstrate that procedural fairness diverges strongly when initiatives are implemented in protected areas or in rural communities. While in the former reserve managers and intermediaries concentrate all decision-making power, initiatives working with rural communities are able to integrate more significantly service providers in management decisions. Marketing ecosystem services in protected areas contributes to reduce expenditure rates for protected area management, but also results in less equitable outcomes, as rural communities and forest resource users become excluded from receiving sustained development benefits. When ecosystem services are commercialised by rural farmers, payments do not cover opportunity costs but act as a significant incentive for participation in most cases. Ecosystem service providers also benefit from complementary project activities, such as forest management training and agricultural extension support. We argue that limited economic impact and existing inequities in decision-making and outcomes can be explained by problems of institutional design, in particular the inability of markets and payments for ecosystem services to account for context-related factors, such as property rights. 相似文献
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