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131.
汶川8.0级地震前区域应力场动态研究 总被引:1,自引:0,他引:1
利用成都、昆明遥测数字地震波形记录资料,研究大量小震震源机制解和视应力值,分析了区域应力场动态和视应力值的时-空分布.给出川青地块平均应力场方位的时间变化.川青地块平均主应力场的方位在汶川8.0级地震前出现明显扰动,同时,地块力轴张量的倾角变化也很明显.得出2006~2007年川青块体逆冲型地震比例偏高,汶川8.0级地震前区域中小地震震源错动类型发生变化的结果,与区域地形变的分析结果是一致的.根据地震波形全波段计算辐射能量,求得的视应力σapp值揭示区域视应力值的微动态起伏过程与区域主压应力场方位的转折类似,可用于地块蕴震物理过程的探索.从汶川8.0级地震前的中短期视应力σapp值的空间分布看,震中所在的龙门山断裂带是低应力分布区,而相对高视应力则分布在外围地区.这些图像可能揭示了汶川8.0级地震前中短期发震构造附近呈现的闭锁现象. 相似文献
132.
In this paper, we use the 12 May 2008 Wenchuan Earthquake as a background event for analyzing and applying the principles of site selection of emergency shelters for a disastrous earthquake. Based on field investigations and analyses of remote sensing imagery, we identified the distribution of active faults and the locations of co-seismic surface rupture zones—areas in which buildings are at risk of intensive damage. It is important that emergency shelters are located outside of such vulnerable areas. One of the lessons learned from the Wenchuan Earthquake is that high fatality rates occur in areas without life-saving shelters. The principles that underlie the selection of emergency shelter sites are as follows: (1) keep far away from active fault zones, with the distance depending on the characteristics of the fault, including the nature of hangingwall and footwall structures; (2) disaster-mitigation strategies should be developed as a multi-dimensional system for the management of natural hazards, human activities, and urban expansion, involving keeping away from vulnerable slopes and establishing an early-warning system; (3) the accessibility of mountainous regions must be considered, including establishing small emergency shelters that house large numbers of people and covering regions with an uneven distribution of villages; and (4) government and law-making agencies in China must establish new earthquake design codes for buildings, emphasizing the importance of public facilities (including schools, collective welfare institutions, and medical facilities) as emergency shelters during disastrous earthquakes. The site-selection process requires an interdisciplinary approach involving seismologists, engineers, environmental and social scientists, emergency management personnel, and government officials. The parameters upon which the above principles are based can be qualitatively determined, thereby providing a valuable initial database for further quantitative analysis. The preliminary results and knowledge gained in the present paper can be used as a decision-making tool to support the government in earthquake-recovery and reconstruction programs. We also discuss practical examples of site evaluation in regions that suffered heavy damage during the Wenchuan Earthquake. 相似文献
134.
Yang Yang Ruan Shaoqin Wu Shifan Chu Jian Unluer Cise Liu Hanlong Cheng Liang 《Acta Geotechnica》2021,16(4):1113-1125
Acta Geotechnica - This paper presents a new microbial technique for soil improvement through microbially induced carbonate precipitation (MICP) incorporating with reactive magnesia cement (RMC).... 相似文献
135.
Quality Control and Evaluation of the Observed Daily Data in the North American Soil Moisture Database 总被引:1,自引:0,他引:1
Weilin LIAO Dagang WANG Guiling WANG Youlong XIA Xiaoping LIU 《Journal of Meteorological Research》2019,(3):501-518
The North American Soil Moisture Database (NASMD) was initiated in 2011 to assemble and homogenize in situ soil moisture measurements from 32 observational networks in the United States and Canada encompassing more than 1800 stations. Although statistical quality control (QC) procedures have been applied in the NASMD, the soil moisture content tends to be systematically underestimated by in situ sensors in frozen soils, and using a single maximum threshold (i.e., 0.6 m3 m-3) may not be sufficient for robust QC because of the diverse soil textures in North America. In this study, based on the in situ soil porosity and North American Land Data Assimilation System phase 2 (NLDAS-2) Noah soil temperature, the simple automated QC method is revised to supplement the existing QC approach. This revised QC method is first validated based on the assessment at 78 of the Soil Climate Analysis Network (SCAN) stations where the manually checked data are available, and is then applied to all stations in the NASMD to produce a more strict quality-controlled dataset. The results show that the revised automated QC procedure can flag the spurious and erroneous soil moisture measurements for the SCAN stations, especially for those located in high altitudes and latitudes. Relative to station measurements in the original NASMD, the quality-controlled data show a slightly better agreement with the manually checked soil moisture content. It should be noted that this quality-controlled dataset may be over-flagged for some valid soil moisture measurements due to potential errors of the soil temperature and soil porosity data, and validation in this study is limited by the availability of benchmark soil moisture data. The updated QC and additional validation will be desirable to boost confidence in the product when high-quality data become available in the future. 相似文献
136.
137.
内蒙古二连盆地、鄂尔多斯盆地典型含铀碳酸型盐湖水、岩两相234U/238U综合分析表明,碳酸型盐湖铀来源于大气降水和潜水对盐湖盆地周围中生代到现代富铀沉积物的溶滤、浸出,具有快速、近源物质来源特点。盐湖卤水和对应沉积物234U/238U值一般为0.8~1.2,湖卤水和潜卤水(晶间卤水)-岩两相中的铀处于沉积平衡状态。早白垩世~上新世含膏盐地层对比研究证实了富铀岩层234U/238U值随铀含量增大而减小,并趋近于1。室内盐湖水蒸发模拟实验发现残余卤水、沉积物234U/238U具有随蒸发程度增大逐渐减小的变化特征。盐湖现代沉积物物相研究发现铀主要以碳酸铀酰和吸附形式赋存在富含有机物和碎屑成分的含盐粘土沉积中,铀在盐类晶体中含量极少,仅存在于封闭水和结晶水中。卤水和沉积物ARu值是盐湖铀源及铀含量水平的指示标志之一。 相似文献
138.
Qian Yuan Xiaofeng Cao Xinbiao Lü Xiangdong Wang Enlin Yang Yuegao Liu Banxiao Ruan Hong Liu Mohammed Abdalla Adama Munir 《中国地球化学学报》2014,33(3):207-220
Kuruqtagh block is the best area for Precambrian geology in Xinjiang Autonomous Region, NW China, since it exposed complete Precambrian lithology units. The study of this ancient base will deepen the understanding of the Precambrian evolution of the Tarim Basin. In this paper, we studied the petrology, geochemistry, zircon LA-ICPMS U-Pb chronology and zircon Hf isotope of Daxigou anorthosite (DA) which is located at the northem margin of Tarim craton and discussed the rock formation, tectonic and geological significance. Zircons from the intrusions display oscillatory zoning and high Th/U ratios (0.39-1.35), implying their magmatic origin. Zircon LA-ICP-MS U-Pb dating results indicate that they formed during the Paleoproterozoic age with the weighted 2~6pb/238U average age of 1818~9 Ma, which is significantly different from former's Neoproterozoic age, and is co- incidentally identical with its associated syenite granite age within the error range. Studies on petrogeochemistry suggest that DA belongs to medium-sodium peraluminous alkaline type, rich in Pb, La, Th and LILE, and poor in HFSE (Gd, Nd, and Ta). The chondrite-normalized REE pattern is slightly to the right form. The average Y~REE is 317.2~ 10-6; HREE show moderate fractionation [average LREE/HREE is 14.71, average (La/Yb)N is 24.77; average (LaJSm)N is 3.85, and average (Gd/Yb)y is 3.46]; and the 6Eu and 8Ce are not obvious. Their initial Hf isotope ratios and Hf two-stage model ages range from -6.6 to -4.43 and 2.63 to 2.74 Ga, respectively. Taken together, it is sug- gested that Daxigou anorthosite is a typical volcanic anorthosite and its primary magma could be contaminated by the partial melt Neoarchaean crust and mainly formed in the arc environment, which recoded the tectonic-magma activities response of the Tarim refers to the amalgamation of the supercontinent Columbia. 相似文献
139.
YANG Yibo FANG Xiaomin LI Minghui APPEL Erwin ZHANG Weilin LIU Xiaoming 《《地质学报》英文版》2014,88(Z1):168-169
正Uranium(U)provides especially useful information for reconstructing paleoredox conditions due to its unique geochemical properties and behavior in supergene environments.The proxy potential under suboxic-oxic 相似文献
140.
This paper extends a previously developed three-part wedge method for the seismic stability analysis of the landfill with a triangular berm using pseudo-static method, and moreover, the translation failure condition of the landfill along under bottom of the berm is only presented. In the seismic impact zone, it is necessary to consider the impact of the seismic force on the stability of the landfill. Generally, apart from the horizontal seismic force, the landfill is also subjected to both upward and downward vertical seismic forces. The downward vertical seismic force has a positive impact on the seismic stability of the landfill, while the upward vertical seismic force is just opposite. Therefore, simply ignoring vertical seismic force, the seismic stability of the landfill will be overestimated or underestimated in the seismic condition. Besides, the seismic yield coefficient is calculated by assuming FSV = 2FS and the ratio of vertical seismic coefficient to horizontal seismic coefficient is equal to 2/3. 相似文献