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51.
During the 1990 Luzon earthquake (Ms 7.8), the central part of Luzon Island, Philippines suffered much from liquefaction-related processes. Examination of inventories
shows that the affected areas lie on certain geological environments that are characteristically vulnerable to liquefaction.
Based on this local experience and the findings of earlier workers correlating geological setting with liquefaction susceptibility,
a first-level map of liquefaction hazard for Laoag City, Northern Philippines, was produced. Distinct micro-geomorphological
units were identified within the mainly fluvio-deltaic setting of the study area. The liquefaction susceptibility of each
unit was then ranked as high, moderate, low or non-liquefiable, taking also the geomorphological evolution of the area into
account. The geomorphological model of the fluvio-deltaic basin was tested against the results of the georesistivity survey
carried out in this study. Moreover, compatibility of the liquefaction susceptibility map with historical liquefaction records
supported the validity of the proposed ranking. The study showed that microzonation based on geomorphological criteria is
indeed very useful in less-developed countries like the Philippines, where funds for a more rigorous determination of liquefaction
potential are limited and not always available. 相似文献
52.
山区地质灾害易发性评价对城镇地质灾害风险管理具有重要意义。本文以康定市为例,以斜坡单元为最小评价单元,选取高程、坡度、坡向、曲率、工程地质岩组、距道路距离、距断裂距离、距水系距离和斜坡结构等9个滑坡影响因子,根据各因子滑坡面积比曲线与证据权值曲线的突变点,划分滑坡影响因子二级状态,并对各影响因子进行相关性分析,剔除相关性较高的距道路距离因子,在此基础上,采用证据权模型进行滑坡易发性评价。对已有治理工程的斜坡单元,本文尝试利用折减系数法对其易发性进行进一步评价。结合现场调查,将研究区滑坡易发性程度划分为:极高易发、高易发、中等易发、低易发。评价结果表明,自然工况下极高易发区主要位于康定市炉城镇以及研究区北侧二道桥村一带,高易发区主要位于雅拉河、折多河与瓦斯沟河谷两侧,对治理工程所在的斜坡单元进行折减后,极高易发区面积由11.21%降至8.42%,滑坡比率由4.03降低至2.3,研究结果符合实际情况,模型精度达77.8%。评价结果较好地反映了康定市区的滑坡易发性分布情况,可为城镇精细化评价提供一定的参考依据。 相似文献
53.
讨论了考古标本中所含矿物的磁学性质与古代地球磁场强度测定数据可靠性之间的关系,进行了岩石磁学实验,包括高温、低温磁化率测定、居里温度测定、磁滞回线各参数的测定等.结果表明,文中所用各类标本(陶片、砖、烧土等)的主要载磁矿物为磁铁矿,采用这些标本用Thellier方法进行逐步热退磁实验所测定的古强度数据较为可靠. 相似文献
54.
55.
56.
《Marine Policy》2015
Ecosystem Based Fisheries Management (EBFM) requires the consideration of potential impacts of a commercial fishery on all components of the ecosystem. Assessment of the impact of commercial fishing on marine mammals generally focuses on species at known risk from bycatch. For cetaceans in particular, inclusion under the Threatened, Endangered and Protected (TEP) species component of Ecological Risk Assessment for the Effects of Fishing (ERAEF) can seem redundant if a species is already known to be at risk or is not thought to interact with the fishery with consequences for its conservation. A spatially and temporally explicit Productivity Susceptibility Analysis (PSA) procedure was developed for inclusion under ERAEF to allow cetacean species to be screened for risk. The technique is demonstrated by assessing the potential risk to harbour porpoise and minke whales from a number of static gear fisheries. The results demonstrate that although a fishery might pose high risk to a species, low or moderate risk areas can exist within the range of the fishery, enabling management measures to focus on areas of greatest risk. Designed to complement and support existing methods of bycatch assessment, this approach is a repeatable and standardised assessment, the outputs of which can be used to systematically document the level of risk posed to different species in a transparent way to aid the inclusion of cetaceans in ERAEF and EBFM both now and in the future. 相似文献
57.
An assessment of the susceptibility to rock slope failure by means of a back-propagation network is proposed for the eastern
portion of the Southern Cross-Island Highway in Taiwan. The model was developed on the basis of six influence parameters of
rock slope instability, which include the rock type, slope aspect, slope angle, joint set number, joint spacing and bedding–slope
relationship. The values of these influence parameters were used as inputs for the network and were classified as nominal
scales in terms of binary numbers, while the state of failure/non-failure of a given slope was assumed to be the output variable.
Data on a total of 170 slopes along the highway was fed into the network for learning. According to the outputs of the network,
the susceptibility to rock slope failure is categorized into four levels, namely low, medium–low, medium and high, which are
mapped along the highway. Three highly susceptible regions are found, which can be viewed as hazardous sections requiring
cautionary measures. Moreover, the proposed model can be used as a tool for determining the possible state of an unfamiliar
rock slope in the context of devising management strategies to be applied to the investigated portion of the highway. 相似文献
58.
GIS-based landslide susceptibility mapping for a problematic segment of the natural gas pipeline,Hendek (Turkey) 总被引:26,自引:0,他引:26
A segment of natural gas pipeline was damaged due to landsliding near Hendek. Re-routing of the pipeline is planned, but it requires the preparation of a landslide susceptibility map. In this study, the statistical index (Wi) and weighting factor (Wf) methods have been used with GIS to prepare a landslide susceptibility map of the problematic segment of the pipeline. For this purpose, thematic layers including landslide inventory, lithology, slope, aspect, elevation, land use/land cover, distance to stream, and drainage density were used. In the study area, landslides occur in the unconsolidated to semi-consolidated clayey unit and regolith. The Wf method gives better results than the Wi method. Lithology is found to be the most important aspect in the study area. Based on the findings obtained in this study, the unconsolidated to semi-consolidated clayey unit and alluvium should be avoided during re-routing. Agricultural activities should not be allowed in the close vicinity of the pipeline. 相似文献
59.
Structural and geomorphological aspects of the Kat landslides (Tokat—Turkey) and susceptibility mapping by means of GIS 总被引:3,自引:0,他引:3
Kat County, which is located in a slope of hilly region and constructed in the side of a mountain along the North Anatolian Fault Zone, is frequently subject to landslides. The slides occur during periods of heavy rainfall, and these events cause destruction to property, roads, agricultural lands and buildings. In the last few decades, a lot of houses and buildings have been damaged and destroyed. Settlement areas have remained evacuated for a long time. The slope instabilities in the study area are a complex landslide extending from north to south containing a lot of landslides. Field investigations, interpretation of aerial photography, analyses of geological data and laboratory tests suggest that some factors have acted together on the slopes to cause the sliding. In the wet season, the slopes became saturated. As the saturation of the earth material on the slope causesa rise in water pressure, the shear strength (resisting forces) decreases and the weight (driving forces) increases; thus, the net effect was to lower the safety factor. Previous failures have affected the rock mass, leading to the presence of already sheared surfaces at residual strengths. The relation between the joint planes and the instability of the slope in the study area was discussed and it was found that the potential slope instabilities are mainly in the directions of NW–SE, NE–SW and N–S. The landslide susceptibility map obtained by using the geographical information system showed that a large area is susceptible and prone to landslides in the northern part of the study area.An erratum to this article can be found at 相似文献
60.
Soil liquefaction susceptibility and hazard mapping in the residential area of Kütahya (Turkey) 总被引:2,自引:0,他引:2
This study presents the results of both field and laboratory tests that have been undertaken to assess liquefaction susceptibilities
of the soils in Kütahya city, located in the well-known seismically active fault zone. Liquefaction potentials of the sub-surface
materials at Kütahya city were estimated by using the geological aspect and geotechnical methods such as SPT method of field
testing. And, the data obtained have been mapped according to susceptibility and hazard. The susceptibility map indicated
“liquefable” and “marginally liquefable” areas in alluvium, and “non-liquefable” areas in Neogene unit for the magnitude of
earthquake of M=6.5; whereas, liquefaction hazard map produced by using of liquefaction potential index showed the severity categories from
“very low” to “high.” However, a large area in the study area is prone to liquefy according to liquefaction susceptibility
map; the large parts of the liquefable horizon are mapped as “low” class of severity by the use of the liquefaction potential
index. It can be said that hazard mapping of liquefaction for a given site is crucial than producing liquefaction susceptibility
map for estimating the severity. Both the susceptibility and hazard maps should be produced and correlated with each other
for planning in an engineering point of view. 相似文献