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改革开放25年,中国城镇化迅速发展,每隔十年经济社会发生一次大变化。第一个十年是上个世纪的80年代,以农村土地家庭承包为动力,推动经济发展上了一个大的台阶。第二个十年是上个世纪的90年代,小平同志南巡讲话以后,中国经济社会以外向型经济发展为重要的动力源, 相似文献
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容量维D0、信息维D1、算法复杂性C(n)与b值的相关性研究x,auto,auto,415px);} hf=httprztl.com >business week launch 总被引:4,自引:1,他引:3 下载免费PDF全文
1问题与思路“八五”地震短临预报攻关号召大家在“新”和“实”字上下功夫,尤其是80年代末、90年代初,适逢地震界兴起非线性热,于是,引进、开发了许多地震学地震预报新指标和新方法,促进了地震预报研究的发展.可是,地震预报的实际水平并未因此发生质的飞跃.... 相似文献
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地层年代确定是地质学研究领域的重要课题,地质类定年方法具有各种不利因素.本文选择地球物理方法确定地层年代,以中国大陆沉积盆地为研究区,通过对盆地中实测速度、深度和年代三者间关系的深入研究,应用统计、拟合和扫描的方法,建立了中国大陆沉积盆地中速度、深度和年代之间的定量关系,此关系式为测定年代提供了一种新的方法.利用此关系式计算了沉积盆地基底的年代范围,并与同位素实测的年龄作了比较,表明该方法可以粗略确定稳定基底年代.计算基底年龄和实测数据之间存在误差,其原因主要是本文把中国大陆沉积盆地看作一个构造单元所致. 相似文献
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从上世纪90年代开始,中国就成为世界上最大的稀土开采国,稀土行业取得了快速发展,占据了国际市场的垄断地位。然而,稀土开发也带来了严重的生态环境破坏。近年来,随着中国稀土产业的转型和国家环保战略地位的确立,如何在稀土行业的发展中保护环境,已成为摆在我们面前的重要课题。 相似文献
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从大陆地震震源的观测研究、震源力学的理论研究和震源物理实验三个方面,评述了90年代以来中国震源物理研究的进展.这些进展包括:大陆地震的震源参数测定;利用数字地震资料进行的“现代”震源参数的反演;地震断裂力学的应用和发展;非线性物理学在震源研究中的应用;岩石破裂实验的发展;地震前兆的物理机制的实验研究等.指出了新技术的发展和现代物理科学的发展对90年代以来震源物理研究的重要影响.展望了跨世纪的我国震源物理研究的发展方向,指出震源物理研究的进展必将在大陆地震预测和减轻地震灾害方面发挥积极的作用. 相似文献
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大地电磁测深是研究地壳和上地幔构造的一种重要的地球物理探测方法,当前国家正在实施深部探测专项SinoProbe等项目,故需要借助于长周期大地电磁测深仪器.我国没有自己生产的长周期大地电磁测深仪器,只能依靠从乌克兰进口的LEMI-417进行深部探测.在LEMI-417使用中,我们从该仪器提供的数据文件Final.asc中发现它的电场信号测量分辨率为0.01 mV/km,磁场信号测量分辨率为0.01 nT,相对较低,此外,该仪器在无GPS信号时会出现记录紊乱等现象,故需要设计适合课题组需要的长周期大地电磁测深仪器.由于大地电磁测深仪器需要采集的电场、磁场信号为微弱信号,容易淹没于噪声之中,故选用了低噪声、极小总谐波失真率的CS3301作为运算放大器.CS3301提供了4种可选择的信号输入模式和7种可选增益,经分析与测试,测量电场信号时,CS3301设置为输入模式1及×64增益,当极距100 M时,测量精度可达0.001 mV/km,高于LEMI-417的0.01 mV/km;测量磁场信号时,将反馈理论用于测量电路,CS3301设置为输入模式3及×64增益,只对信号的可变部分进行放大,精度可达0.006 nT,高于LEMI-417的0.01 nT.该系统在华南的9005、1005等多个测点以及东北的1600、5105等多个测点进行了测试,并与LEMI-417进行了对比试验,测量结果表明它们的时间序列曲线比较一致,数据处理后,在同一测点得到的大地电磁测深曲线也较一致,说明设计的仪器达到了预期目标. 相似文献
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Anne Pommier 《Surveys in Geophysics》2014,35(1):41-84
Magnetotelluric (MT) surveying is a remote sensing technique of the crust and mantle based on electrical conductivity that provides constraints to our knowledge of the structure and composition of the Earth’s interior. This paper presents a review of electrical measurements in the laboratory applied to the understanding of MT profiles. In particular, the purpose of such a review is to make the laboratory technique accessible to geophysicists by pointing out the main caveats regarding a careful use of laboratory data to interpret electromagnetic profiles. First, this paper addresses the main issues of cross-spatial-scale comparisons. For brevity, these issues are restricted to reproducing in the laboratory the texture, structure of the sample as well as conditions prevailing in the Earth’s interior (pressure, temperature, redox conditions, time). Second, some critical scientific questions that have motivated laboratory-based interpretation of electromagnetic profiles are presented. This section will focus on the characterization of the presence and distribution of hydrogen in the Earth’s crust and mantle, the investigation of electrical anisotropy in the asthenosphere and the interpretation of highly conductive field anomalies. In a last section, the current and future challenges to improve quantitative interpretation of MT profiles are discussed. These challenges correspond to technical improvements in the laboratory and the field as well as the integration of other disciplines, such as petrology, rheology and seismology. 相似文献
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回顾与展望——21世纪的固体地球物理 总被引:3,自引:13,他引:3
回顾了20世纪固体地球物理学的发展历程和对地球科学发展的贡献,阐述了地球物理学在社会发展中的先导作用和地位,并以中国反射地震方法取得巨大成功的实例,说明国民经济建设的巨大需求,是地球物理学发的重要动力。最后,给出了21世纪地球物理学的发展方向和研究重点,强调地球物理学科要与时俱进,改革创新。 相似文献
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分析了近百年来中国大陆强震的时间与空间分布。强震活动具有在时间上的起伏特征与空间上集中分布于主体地区的特征。综合考虑时间、空间的分布特征的动态变化 ,进一步阐明了微动态期划分的意义 ,并且与活动 -平静期进行了对比。中国及其邻区大陆强震的个体行为具有丛集性。近百年来存在一种大约 13a的阶段 ,反映了大范围的地震能量积累的起伏发展过程。与时间轴上的相对高潮期相对应 ,各期存在 1个地震活动主体地区与另 1个次活动区 ,2个大震活动区的相对位置往往分别处于青藏高原的两侧。相当部分的强震孕育是在原有孕震区继续进行的 ,而多数强震的孕育是在原有区域外进行的。活跃期与平静期的划分对理解时间分布的不均匀性是有意义的 ,然而活动期的长短不一 ,强度不同 ,活动期内也有起伏。从强震活动的孕育过程看 ,微动态期的划分更有利于对强震空间分布的预测 相似文献
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本文从大地电磁扬的色散关系出发,阐述了进行大地电磁资料一维联合反演的物理意义。论证了对于以色散关系相联系的一对大地电磁响应函数,特别是阻抗实部和虚部视电阻率进行联合反演的必要性和可能的应用前景。对比研究了大地电磁阻抗各单参量及其联合反演的效果。结果表明,在加快反演迭代速度,限定反演解的非唯一性、保证反演迭代的稳定进行等方面,联合反演比单参量反演具有明显的优越性;在大多数情况下,阻抗实部视电阻率和阻抗虚部视电阻率联合反演的效果要比通常所采用的常规视电阻率和阻抗相位的联合反演效果好。实际大地电磁资料的试验表明,各种不同平均阻抗的利用和综合反演解释将有助于获得更为可靠的结果。 相似文献
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作为地震探测的有效补充,电磁法在海洋油气资源勘探中发挥着越来越重要的作用.本文针对海洋电磁法中极低时钟误差、大动态范围采集等要求,提出使用GPS和高精度原子钟解决低时钟漂移问题;采集电路中设计增益可调的放大电路,MCU通过对采集到的信号进行实时分析,实现增益动态调整,解决海洋电磁信号大动态范围采集问题;研制的海洋电磁信号数据记录单元每天时间误差小于0.3 ms、电场通道动态范围可以达到160 dB、磁场通道动态范围可以达到134 dB.通过在室内指标测试、室外试验,表明设计的数据记录单元能够稳定可靠工作.为证明数据纪录单元的有效性,将数据记录单元和国外商用MT仪器进行野外一致性对比实验,数据记录单元与商用仪器结果基本一致;在水深100 m海域进行了海底MT信号采集,得到了有效的结果.该研究为海洋电磁信号低时钟漂移、大动态范围采集提供了一种有效解决方案. 相似文献
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《中国科学:地球科学(英文版)》2017,(11)
Fourteen countries share about 22000 km land border with China, but not much is known about the variation in vegetation in such a large diverse area. By employing the remotely-sensed vegetation indices the vegetation greenness along the border was discussed. Our results show that since the early 21 st century, similar trends in vegetation greenness have occurred along most of China's border, but differences occurred on either side of the border. Along the border with North Korea and South Asian nations, greater increasing trend in vegetation greenness occurred inside China's border, suggesting that China's vegetation protection programs have been successful. Spatial and temporal variations in vegetation greenness trends were observed along China's border with Russia, Mongolia, and Central Asian nations. Vegetation variation was lower inside China, along the Russian border, and China's eastern border with Mongolia. Along most borders with Central Asian nations, rates of vegetation change inside China's border during the growing season were higher than the rates outside the border. The results suggest that social customs, resource exploitation patterns, and national environmental conservation programs may profoundly affect vegetation greenness. 相似文献
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Ümİt Avşar Erşan Türkoğlu Martyn Unsworth İlyas Çağlar Bülent Kaypak 《Pure and Applied Geophysics》2013,170(3):409-431
The collision between the Arabian and Eurasian plates in eastern Turkey causes the Anatolian block to move westward. The North Anatolian Fault (NAF) is a major strike-slip fault that forms the northern boundary of the Anatolian block, and the Erzincan Basin is the largest sedimentary basin on the NAF. In the last century, two large earthquakes have ruptured the NAF within the Erzincan Basin and caused major damage (M s = 8.0 in 1939 and M s = 6.8 in 1992). The seismic hazard in Erzincan from future earthquakes on the NAF is significant because the unconsolidated sedimentary basin can amplify the ground motion during an earthquake. The amount of amplification depends on the thickness and geometry of the basin. Geophysical constraints can be used to image basin depth and predict the amount of seismic amplification. In this study, the basin geometry and fault zone structure were investigated using broadband magnetotelluric (MT) data collected on two profiles crossing the Erzincan Basin. A total of 24 broadband MT stations were acquired with 1–2 km spacing in 2005. Inversion of the MT data with 1D, 2D and 3D algorithms showed that the maximum thickness of the unconsolidated sediments is ~3 km in the Erzincan Basin. The MT resistivity models show that the northern flanks of the basin have a steeper dip than the southern flanks, and the basin deepens towards the east where it has a depth of 3.5 km. The MT models also show that the structure of the NAF may vary from east to west along the Erzincan Basin. 相似文献
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Magnetotelluric (MT) studies represent the structure of crust and mantle in terms of conductivity anomalies, while geodynamic modelling predicts the deformation and evolution of crust and mantle subject to plate tectonic processes. Here, we review the first attempts to link MT models with geodynamic models. An integration of MT with geodynamic modelling requires the use of relationships between conductivity and rheological parameters such as viscosity and melt fraction, which are provided by laboratory measurements of rock properties. Owing to present limitations in our understanding of these relationships, and in interpreting the trade-off between scale and magnitude of conductivity anomalies from MT inversions, most studies linking MT and geodynamic models are qualitative rather than providing hard constraints. Some recent examples attempt a more quantitative comparison, such as a study from the Himalayan continental collision zone, where rheological parameters have been calculated from a resistivity model and compared to predictions from geodynamic modelling. We conclude by demonstrating the potential in combining MT results and geodynamic modelling with examples that directly use MT results as constraints within geodynamic models of ore bodies and studies of an active volcano-tectonic rift. 相似文献