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1.
We evaluate the seismic moment–frequency relation for the Harvard catalogue in the period 1977–1994. This catalogue is composed of about 12 000 earthquakes. After selection of events in terms of depth and energy, we retain about 8000 data points. We estimate two parameters of the seismic moment distribution: the power exponent β and the cut-off value M m . The method used is a least-squares linear fit on a log–log scale performed over a range selected on the basis of the standard deviation from the histogram. The analysis is carried out for different subdivisions of the Earth in square grids of different sizes. Neither parameter exhibits a dependence on cell size, suggesting the universality of their values and the interpretation of the existence of a cut-off as a finite size effect linked to a finite catalogue length. The variations of the parameters are investigated as a function of time (duration of the catalogue) and versus the number of events used for building up the distribution. Again, β and M m do not depend on time, but M m depends on the number of events, reaching a stable value for N ≈ 1000. The only significant change in the parameters is observed for different values of M 0upper in the catalogue, revealing the existence of universality classes. 相似文献
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Based on the statistical method and the historical evolution of meteorological stations, the temperature time series for each station in Hunan Province during 1910–2014 are tested for their homogeneity and then corrected. The missing data caused by war and other reasons at the 8 meteorological stations which had records before 1950 is filled by interpolation using adjacent observations, and complete temperature time series since the establishment of stations are constructed. After that, according to the representative analysis of each station in different time periods, the temperature series of Hunan Province during 1910–2014 are built and their changes are analyzed. The results indicate that the annual mean temperature has a significant warming trend during 1910–2014 and the seasonal mean temperature has the largest rising amplitude in winter and spring, followed by autumn, but no significant change in summer. Temperature variation over Hunan Province has several significant warm-cold alternations and more frequent than that in whole China. Annual and seasonal mean temperatures except summer and autumn have abrupt warming changes in the recent 100 years. The wavelet analysis suggests that the annual and four seasonal mean temperatures in recent 100 years have experienced two climatic shifts from cold to warm. 相似文献
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《Geomorphology》2002,42(1-2):97-116
Geological and geomorphological surveys have been performed in the area affected by the 1997–1998 Umbria–Marche seismic sequence (Mmax=6.0) aimed at defining the Quaternary tectonic history and the characteristics of the present tectonic regime. Data have been collected from: (1) the analysis of the remnant landsurfaces by means of aerial photos and field surveys; (2) geological surveys in the Cesi–San Martino basin and in the easternmost sector of the Colfiorito basin in order to identify deformative features affecting the Quaternary deposits; (3) the analysis of boreholes and geo-electrical data (derived from previous surveys performed in the 1960s) in order to reconstruct the top of the pre-Quaternary substratum in the Colfiorito basin. Two different successions of remnant landsurfaces have been identified along the faults bounding the basins to the east, in the hangingwall and the footwall, respectively. The difference accounts for a fault-controlled evolution of the landscape at least during the Upper Pliocene–Early Pleistocene. The deformation affecting the Quaternary deposits and landforms in the investigated basins indicates a decreasing tectonic activity along the master faults since the Middle Pleistocene. Surface deformation due to tectonics is faint and displayed by gentle warping of the landforms during the late Quaternary. As for the basin geometry, subsurface data show that two minor depressions formed in the Colfiorito Basin during the Quaternary, the oldest one close to the fault bounding the basin, while the youngest (and deepest) formed in the inner portion of the basin. Therefore, the present geometry is different from that of other fault-bounded Quaternary depressions of the central Apennines (typically half-graben basins), showing the maximum depth of the substratum in the area close to the master fault. Tectonic history may be summarised as follows: (1) origin of the Quaternary fault-bounded Colfiorito and Cesi–San Martino basins; (2) evolution of the basins with a half-graben style; (3) significant reduction of tectonic activity since the Middle Pleistocene. During the third phase, the evolution of the basins is no longer related to a half-graben style. In the case of the Colfiorito basin, a new depression is superimposed to on the previous half-graben whose evolution is related to the lowering of the inner portion of the basin through warping. Moreover, present activity does not result in fault-related surficial displacements but only in “continuous” deformation spread over the basins. These conclusions have fundamental implications for the seismotectonic framework of the 1997–1998 earthquake sequence. This deformation style is, indeed, in agreement with the coseismic deformation modelled by means of the SAR interferometry analyses carried out by other institutions during the seismic sequence, and with the lack of evident surface faulting related to the mentioned events in the investigated area. This evidence indicates that the evolution of the investigated area since the Middle Pleistocene resulted from the summation of deformative episodes similar to that which occurred during the recent seismic sequence. As a consequence, no earthquakes with magnitude larger than 6 are expected in the area. 相似文献
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We discuss the issues related to the human colonization of the Tuva landscapes in the Scythian time. An analysis is made of the spatial and landscape confinedness of archaeological sites having regard to the Late-Holocene rhythms of climate change in the mountains. For the historical-landscape analysis the MapInfo 12.0 GIS technologies were used in compiling the landscape map of the Tyva Republic, the scheme of physical-geographical regionalization and the schematic map of spatial distribution of archaeological sites from the Scythian time. The then most developed landscapes include the steppe mountain-valley and forest-steppe low- and mid-mountain landscapes, which was associated with the main economic sector, namely nomadic stockbreeding. The culture of the Scythian time existed under a colder and more humid climate than at present. An increase in humidity in originally dry areas led to an increase in steppe vegetation productivity growing in depressions and on slopes of mountain ranges. These factors created favorable conditions for the development of nomadic stockbreeding. A spatial analysis of the distribution of archaeological sites in the physical-geographical provinces of Tuva intimates that depression landscapes were colonized mostly in the Scythian time. The Tuvinian depression province (the archaeologically richest area of Tuva) and the Ubsunur depression account for 52 and 21% of the sites, respectively. The mountain landscapes were colonized to a considerably lesser extent; the largest number of sites are located in the Western-Tuva mountain province. In the Scythian time, the cores of development of the Tuva territory were represented by the intermontane depressions (Tuvinian and Ubsunur), the connections between which were provided by a small number of large valleys and mountain passes. 相似文献
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The characteristic features of the transformation of the territorial geospace structure in the African Christianity religious geospace during 1910–2010 have been revealed. African countries within the boundaries of 2010 are used as territorial cells that have been fixed retrospectively over the course of the period analyzed. We used indicators, such as Ryabtsev’s index of relative structural shifts and the trajectory of the demographic center of the Christianity to assess changes in the inertia level of the territorial structure for the entire time interval as a whole and for each of the components of its 20-year long periods. It is found that to date the adherents of Christianity are extremely unevenly distributed in the countries of Africa; however, over the course of the period under consideration there was taking place a homogenization of their settlement. In accordance with changes of the values of the indicators used, we identified two development stages of geospace of African Christianity: colonial and post-colonial. It is determined that the colonial stage (1910–1970) is characterized by a “compression” of territorial structure from east and north, and by a predominance of the south-westward direction of movement of the demographic center because of a decrease in the proportion in the Christian population of East Africa first on account of Egypt and Ethiopia and Madagascar (1910–1930) and then North Africa on account of Egypt and Algeria (1930–1950). The territorial structure of Christianity’s geospace during the post-colonial stage is characterized by a higher degree of inertia at the background of the westward ”expansion” and the “compression” from the south as well as by a change of the vector of movement of the demographic center for north-westward. 相似文献
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S.Ting 《地理学报(英文版)》1947,(2)
In May 1945, the author flew to Urumuchi vis the Kansu Corridor. There are evidently streamflood cournes on the no 'thern front the Chilienshan and great pediments have been formed. Former erosional surface on the Chilienshan were seen in two localities. They ars well preserved flat-topped benches sloping towards the north; and flanked by gullies, These lie at the altitude 3,200 meters above the sea. 相似文献
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In May 1945, the author flew to Urumuchi vis the Kansu Corridor. There are evidently streamflood cournes on the no 'thern front the Chilienshan and great pediments have been formed. Former erosional surface on the Chilienshan were seen in two localities. They ars well preserved flat-topped benches sloping towards the north; and flanked by gullies, These lie at the altitude 3,200 meters above the sea. 相似文献
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Deinstitutionalisation of psychiatric patients since the 1980s has introduced a new population and a new land use to New Zealand's urban areas. This paper reviews the geography of deinstitutionalisation, and investigates whether the North American phenomenon of a service-dependent ghetto can be identified in Dunedin. 相似文献
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George W. Wenzel 《Polar research》2009,28(1):89-99
Considerable attention has been devoted to the possible effects of global climate change on the environment of the circumpolar world. With regard to the Inuit, the aboriginal culture of Arctic Canada, research interest has focused principally on the vulnerability of the hunting and harvesting component of the traditional food system, otherwise frequently referred to as the subsistence system, if wild terrestrial and marine resources become less available. Although also concerned with the traditional Inuit food economy, this paper concentrates on the customary institutional mechanisms by which the Inuit distribute and share the products obtained from hunting. After analysing this social economy, a review of the data on recent climate-related range changes of a number of Arctic animal populations is carried out, in terms of how projected environmental changes may affect this other aspect of Inuit subsistence. After tentatively concluding that some species substitution and/or replacement will occur, the final aspect of the paper considers the potential for the possible exclusion of these "replacements" as a result of the political aspect of climate change. 相似文献
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Do perceptions of the Red‐tailed Hawk indicate a human‐wildlife conflict on the island of La Gonave,Haiti? 
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下载免费PDF全文 Justin White Lisa M. Kennedy Maria Elisa Christie 《Singapore journal of tropical geography》2017,38(2):258-268
The Caribbean subspecies of the Red‐tailed Hawk (Buteo jamaicensis solitudinus or B.j. jamaicensis) is the largest native carnivore on the island of La Gonave, Haiti, and the island's apex predator. On other Caribbean islands, raptors have been persecuted by local people typically because of their depredation of livestock. In addition to possible persecution from humans, Red‐tailed Hawks on La Gonave face challenges from island‐wide timber overharvest and rapid land‐cover changes. To better understand the human‐apex predator relationship on La Gonave, we surveyed islanders about their perceptions of, and interactions with, the Red‐tailed Hawk. According to 121 respondents from 10 villages, La Gonavans do not hunt, kill, or consume Red‐tailed Hawks. Our study revealed a notable absence of negative perceptions of the hawk by respondents despite intense hawk depredation of domestic chickens. While the chicken depredation may lead outside observers to consider the human‐hawk relationship on La Gonave as representative of a human‐wildlife conflict, our interview data do not support that conception. Our findings reflect an important conversation in related contemporary scientific literature about what constitutes human‐wildlife conflicts across various cultures. Despite tolerance by residents, Red‐tailed Hawks on La Gonave remain threatened by habitat degradation. 相似文献
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CLUNY MACPHERSON 《New Zealand geographer》1999,55(2):50-59
This paper examines the circumstances in which ethnic labels and identities are constructed and the conditions that are producing socio-cultural divergence within them. Using Samoan identities as an example, it is argued firstly that categories based on descent will not necessarily reflect socio-cultural realities within them and, secondly, that Samoan identities constructed at various times for particular purposes may have given an impression of ethnic unity which masked considerable internal divergence. Finally, it is argued that it may be increasingly difficult for migrant Samoans to agree on symbols of Samoan identity, much less to agree on whether or not these might be building blocks of a national identity. This fluid reality raises fundamental issues about the significance of the apparently fixed descent categories with which we all routinely work. 相似文献
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Migration‐as‐development repackaged? The globalizing imperative of the Singaporean state's diaspora strategies 下载免费PDF全文
下载免费PDF全文 Diaspora strategizing is becoming an important field of public policy in countries that seek to advance development through migration. Diaspora strategies present a way of complicating interpretations of development, as countries that represent different levels of development seek to mobilize diaspora networks nonetheless. While Singapore's diaspora strategies prioritize diaspora knowledge networks, it bears the stamp of the country's colonial history, postcolonial priorities and developmental state apparatus. We suggest that these factors result in a distinctive diaspora strategy characterized by a centralized and technocratic approach more similar to diaspora strategies found in emerging economies. Earlier research on diaspora strategies has been concerned with assessing successes or failures, but a more critical scholarship that questions the logics and outcomes of diaspora strategizing is emerging. We bring the Singaporean case into dialogue with four such critiques: first, the intellectual foundations of diaspora‐centred development; second, the hyperextension of state infrastructure for emigration and stakeholder alignment; third, the selective mobilization of the idea of diaspora; and fourth, the evidence base upon which diaspora‐centred development is predicated. Our goal is to further critical interrogation into the logics, efficacy and sustainability of diaspora strategizing. We situate our analyses in the international literature on diaspora knowledge mobilization. 相似文献
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Tad W. Patzek 《Natural Resources Research》2010,19(1):1-9
The continuously decreasing average coal rank (heating value), inadequate investment, and ever stricter air-emission controls
have caused the average efficiency of electricity generation from coal in the U.S. to plummet to a mere 32% by the year 2008.
The U.S. gas-fired powerplants are 30% more efficient than the coal-fired ones, with average efficiency of 43% in 2008. Replacing
each 1,000 MW
e
generated by an average coal-fired powerplant with an average gas-fired powerplant would avoid today 7 million tonnes of CO2 emissions, 1.2 million tonnes of toxic ash, and significant issues with water contamination. The parallel upgrades to the
more efficient supercritical steam turbines would decrease current emissions by up to 50% (from the current average plant
efficiency of 32% to over 45%). The CO2 captured in the new combined-cycle powerplants might be used to enhance oil recovery in local fields, where feasible. The
CO2 enhanced oil recovery (EOR) can never become the main sink for the gigantic CO2 volume generated each year by electric powerplants. Currently, EOR could absorb only 1% of that volume. 相似文献
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本项研究选取柴达木盆地尕斯库勒盐湖区作为研究区,筛选出了9种优势盐生植物,开展了盐生植物生长区土体颗粒、容重、含水量等物理性质指标,以及土体中HCO<sub>3</sub><sub><sup>-</sup></sub>、Cl<sub><sup>-</sup></sub>、SO<sub>4</sub><sub><sup>2-</sup></sub>、K<sub><sup>+</sup></sub>、Na<sub><sup>+</sup></sub>、Ca<sub><sup>2+</sup></sub>和Mg<sub><sup>2+ </sup></sub>7种易溶盐离子含量试验测试,分析了区内芦苇、海韭菜等9种盐生植物茎叶和根系部分HCO<sub>3</sub><sub><sup>-</sup></sub>、Cl<sub><sup>-</sup></sub>等7种易溶盐离子含量及其分布规律。在此基础上,探讨了区内9种盐生植物对易溶盐离子吸收作用及其差异性;采用盐生植物地上茎叶部分K<sub><sup>+</sup></sub>/Na<sub><sup>+</sup></sub>值结果,定量评价了区内9种盐生植物耐盐性及变化规律,结果表明,区内9种盐生植物茎叶部分K<sub><sup>+</sup></sub>/Na<sub><sup>+</sup></sub>比值,其由大至小依次为：小花棘豆0.84、羊齿天门冬0.58、白刺0.55、盐地风毛菊0.52、海韭菜0.50、无脉苔草0.47、洽草0.41、芦苇0.39和赖草0.34。本项研究结果,利用为尕斯库勒湖区及其周边地区,利用盐生植物有效改良土壤盐渍化方面提供理论支撑。 相似文献
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Kenya's Standard Gauge Railway (SGR), and its construction and financing by China, exemplifies the prominence accorded to mega‐infrastructural projects in contemporary economic development, as well as the dependence this has engendered on external loans. Alongside, multiple geographies intertwine in the SGR which is both a component of China's global ‘Belt and Road Initiative’ (BRI), as well as an East African regional link between coastal Kenya and neighbouring landlocked countries. In most popular and academic analyses, the role of China is emphasized over the SGR's positioning within East Africa. Does this then lead to an undermining of the meanings that are attached to the SGR within Kenya? This article seeks to add Kenyan perspectives to the debate over China's infrastructural loans by examining the range of news media discourses that have emerged around the SGR. Utilizing the theoretical lens of South‐South cooperation and African agency, this study analyzes how material infrastructure becomes meaningful within the context of a political superstructure. For Kenya, this political superstructure is shaped not only by Kenya‐China relations, but also by infrastructural competitions within East Africa, as well as within Kenya itself. 相似文献