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41.
Application and verification of fuzzy algebraic operators to landslide susceptibility mapping 总被引:4,自引:2,他引:4
Saro Lee 《Environmental Geology》2007,52(4):615-623
The aim of this study was to apply and to verify the use of fuzzy logic to landslide susceptibility mapping in the Gangneung
area, Korea, using a geographic information system (GIS). For this aim, in the study, a data-derived model (frequency ratio)
and a knowledge-derived model (fuzzy operator) were combined. Landslide locations were identified by changing the detection
technique of KOMPSAT-1 images and checked by field studies. For landslide susceptibility mapping, maps of the topography,
lineaments, soil, forest, and land cover were extracted from the spatial data sets, and the eight factors influencing landslide
occurrence were obtained from the database. Using the factors and the identified landslide, the fuzzy membership values were
calculated. Then fuzzy algebraic operators were applied to the fuzzy membership values for landslide susceptibility mapping.
Finally, the produced map was verified by comparing with existing landslide locations for calculating prediction accuracy.
Among the fuzzy operators, in the case in which the gamma operator (λ = 0.975) showed the best accuracy (84.68%) while the
case in which the fuzzy or operator was applied showed the worst accuracy (66.50%). 相似文献
42.
43.
Miki Chiba 《Natural Hazards》2011,56(2):499-507
On July 19, 2006, several sediment-related disasters (debris flows and landslides) occurred in Okaya and Suwa, Nagano Prefecture,
Japan. In Okaya, neither the municipal government nor the residents had expected such a disaster, and they were unprepared.
No evacuation of the population took place prior to the disaster, and two debris flows killed eight people. Another debris
flow struck a retirement home. Fortunately, the first-floor residents could be evacuated to the second floor. In contrast,
the nearby town of Suwa was evacuated voluntarily before the debris flow struck, and no fatalities occurred. This paper describes
the situation at the time of the disaster, the evacuations in Okaya and in Suwa, and their consequences from the point of
view of disaster-prevention personnel and retirement-home staff. Factors that should be considered in formulating warning
and evacuation systems in response to sediment-related disasters are discussed. 相似文献
44.
45.
Tim R. Orr 《Bulletin of Volcanology》2011,73(3):335-346
Shatter rings are circular to elliptical volcanic features, typically tens of meters in diameter, which form over active lava
tubes. They are typified by an upraised rim of blocky rubble and a central depression. Prior to this study, shatter rings
had not been observed forming, and, thus, were interpreted in many ways. This paper describes the process of formation for
shatter rings observed at Kīlauea Volcano during November 2005–July 2006. During this period, tilt data, time-lapse images,
and field observations showed that episodic tilt changes at the nearby Pu‘u ‘Ō‘ō cone, the shallow magmatic source reservoir,
were directly related to fluctuations in the level of lava in the active lava tube, with periods of deflation at Pu‘u ‘Ō‘ō
correlating with increases in the level of the lava stream surface. Increases in lava level are interpreted as increases in
lava flux, and were coincident with lava breakouts from shatter rings constructed over the lava tube. The repetitive behavior
of the lava flux changes, inferred from the nearly continuous tilt oscillations, suggests that shatter rings form from the
repeated rise and fall of a portion of a lava tube roof. The locations of shatter rings along the active lava tube suggest
that they form where there is an abrupt decrease in flow velocity through the tube, e.g., large increase in tube width, abrupt
decrease in tube slope, and (or) sudden change in tube direction. To conserve volume, this necessitates an abrupt increase
in lava stream depth and causes over-pressurization of the tube. More than a hundred shatter rings have been identified on
volcanoes on Hawai‘i and Maui, and dozens have been reported from basaltic lava fields in Iceland, Australia, Italy, Samoa,
and the mainland United States. A quick study of other basaltic lava fields worldwide, using freely available satellite imagery,
suggests that they might be even more common than previously thought. If so, this confirms that episodic fluctuation in lava
effusion rate is a relatively common process at basaltic volcanoes, and that the presence of shatter rings in prehistoric
lava flow fields can be used as evidence that such fluctuations have occurred. 相似文献
46.
The distribution and abundance of euphausiid larvae and salps was studied from samples collected in 2002 and 2006 from Prydz Bay, Antarctica.Larvae of Thysanoessa macrura and Euphausia superba were mainly distributed in the north of the continental shelf. T. macrura was more abundant and had a relatively wider distribution. In 2006, with ice having retreated and higher seawater temperatures and chlorophyll a levels, E. superba and T. macrura occurred in higher abundances and at more mature developmental stages. Euphausia crystallorophias was mainly distributed in the neritic region. In 2002, with severe ice conditions in the neritic region, abundance of E. crystallorophias was consisted of metanauplius (MN) and calyptopis I (CI). Salps, mostly Salpa thompsoni, had a low abundance in Prydz Bay. In 2002, S. thompsoni was only m)-3. In 2006, S. thompsoni was found at three stations located near the contimental factors, such as the timing of ice melt, polynya formation and food concentration appear to have a marked effect on the distribution and abundance of euphausiid larvae and salps. 相似文献
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