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This study attempts to use the geographic information system (GIS) technique to map and understand the tectonics and crustal structures of Pakistan. Maps of surficial tectonic features and seismological parameters including Moho depth, Pn velocity and Pg velocity are complied. Based on the seismological data-set of the country the earthquake hazard map of Pakistan is also presented by applying regression technique on seismological, geological and topographical parameters. A case study of 8 October 2005 earthquake is used to validate the hazard map. It is envisaged that the developed GIS database would help policy-makers and scientists in natural hazard evaluation, seismic risk assessment and understanding of earthquake occurrences in Pakistan. 相似文献
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Ian L. Turner Paul E. Russell Tony Butt Chris E. Blenkinsopp Gerd Masselink 《Coastal Engineering》2009
This paper replies to TE Baldock's discussion [Coastal Eng. 56 (2009) 380–381] of ‘Measurement of wave-by-wave bed-levels in the swash zone’ by Turner et al. [Coastal Eng. 55 (2008) 1237–1242]. We address and extend the comparison and discussion of ultrasonic bed-level sensors and buried pressure transducers to obtain estimates of the beach face elevation within the swash zone. We demonstrate the use of the former method to obtain many and continuous (every time the beach face is exposed) in-situ estimates of net sediment flux per swash. 相似文献
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A technique is described to observe and quantify wave-by-wave bed-level changes in the swash zone. The ultrasonic instrument system is non-contact with the beach face surface being measured and the sensors remain outside of the fluid flows causing sediment movement. Sensor resolution combined with the electronic noise inherent within a digital network data-logging system results in a (conservative) measurement accuracy of ± 1 mm, equating to a couple of sand grain diameters in height. Illustrative field results demonstrate the practical use of the instrumentation, and a simple data pre-processing method to separate swashes and intervening bed-level ‘events’ is discussed. These example data reveal rather complex fluctuations of the bed observed over time periods of minutes to hours. Rather strikingly, gross bed-level changes per wave are revealed to be up to many orders of magnitude larger than the observed net rate of beach face evolution. It is outlined how observations of successive bed-level changes at multiple locations within a dense grid, combined with a consideration of sediment continuity, will now enable the total net sediment transported per uprush–backwash to be quantified. 相似文献
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A simple analytical model is developed from which we have calculated the temperature throughout the lunar interior resulting
from internal heat sources and the imposition of surface temperature boundary conditions. The surface temperature is determined
almost entirely by the balance of solar heating and surface reradiation; as a consequence this temperature is latitude dependent,
decreasing towards the lunar poles. The internal solution shows that the latitude effect exists almost undiminished to great
depths within the Moon.
It is suggested that this dependence on latitude may have a significant effect on the Moon’s thermal evolution. Using the
liquefaction model the high concentration of lunar maria at low latitudes may be explained. 相似文献
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A regional geochemical stream sediment survey of part of Northern Ireland led to the recognition of three types of base metal anomaly of exploration interest. These were significant anomalies of both elastic and hydromorphic origin, and non-significant hydromorphic anomalies in several upland areas. The significant anomalies are derived from Pb-Zn-Cu mineralization, whereas the non-significant anomalies are due to the leaching of Zn and other metals from acidic and/or gleyed soils and subsequent concentration in stream channels by coprecipitation with manganese oxides. Significant hydromorphic anomalies can be identified on the basis of abnormal Zn/Mn ratios and significant elastic anomalies on the basis of anomalous Pb contents. It is of the utmost importance to distinguish the dispersion mechanisms. Regional variations in bedrock geochemistry may only be identified when consideration is given to local dispersion mechanisms and account taken of the effects of variations in the surface environment on stream sediment composition. Changes in vegetation and land use may lead to rapid alterations in the nature of the dominant dispersion mechanisms. 相似文献
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The paper compares ethnic change and diversity across two recent decades using common group and area definitions. Ethnic minority groups are shown to be growing rapidly at 41 per cent between 1981 and 1991 and 39 per cent between 1991 and 2001. Some groups have grown swiftly (Black Africans, Bangladeshis), while others have seen moderate expansion (Indians, Other Asians). The White population has hardly grown and the White British population has probably declined. Black and Ethnic Minority (BEM) populations remain concentrated in metropolitan areas in 2001 as in 1991 and 1981. Whereas between 1981 and 1991, BEM groups were concentrating into metropolitan areas, between 1991 and 2001 deconcentration began for most groups. The London region stands out as highly dominant, housing more than 50 per cent of BEM populations as a whole in 1991 and 2001. However, between 1991 and 2001, BEM groups grew outside their core areas. The consequence of BEM population growth and spread has been a dramatic increase in ethnic diversity in all regions. 相似文献
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Natural Hazards - Ecological processes such as landslide disaster are primarily impacted by both geological and land use activities happening at different spatiotemporal scale. They specifically... 相似文献
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Kristie L. Ebi Jonathan Padgham Mamadou Doumbia Alpha Kergna Joel Smith Tanveer Butt Bruce McCarl 《Climatic change》2011,108(3):423-436
This study was undertaken to assess the potential impacts of climate change on agriculture in the Sikasso region of southern
Mali, as part of an effort by the U.S. Agency for International Development (USAID) to integrate climate change adaptation
considerations into their development projects. The region is considered to be the breadbasket of Mali, providing a substantial
amount of the country’s food supplies as well as cotton for exchange earnings. The project had two components: modeling how
climate change could affect production of cereal and cash crops in southern Mali; and conducting a stakeholder-driven vulnerability
and adaptation assessment to identify potential options for addressing current and projected risks to agriculture from climate
change. Projected changes in crop yields were based on a previous analysis that was extended for the purposes of this study.
The projections suggested that the sensitivity of maize to changing weather conditions is relatively small (generally less
than 10% change) under both dry and wet scenarios in 2030 and 2060. White (Irish) potatoes, the primary cash crop, are the
most sensitive to changing weather conditions, with yields decreasing under both dry and wet conditions; yields could decrease
by about 25% by 2060. Stakeholder workshops, field interviews, and an expert analysis were used to assess current and future
climate-related vulnerability and to identify potential adaptation options. The main focus of the assessment was farmers in
a village of about 3,000 people in the Sikasso region that practiced a rice-potato rotation system typical to the region.
The farmers emphasized adaptation measures that require outside financial and technical assistance, for example installation
of a water gate that would retain more water in the inland valley and increase the water table to flood rice fields during
the rainy season and for furrow irrigation of potatoes during the dry season. Adaptations emphasized by both the farmers and
representatives of regional technical services were crop diversification and germplasm improvement; soil and water management;
access to equipment (plows, carts, oxen, and improved stoves); credit stockage villageois (CSV); and fertilizer. 相似文献