库玛断裂带强震活动与地震空区研究   总被引：12，自引：0，他引：12  

陈玉华  马文静 《地震》2002,22(2):81-87

库玛断裂带作为青藏高原内部的一条强地震活动带, 1900年以来发生过3次7级地震,其中2次7级大震前均出现5级以上地震的背景空区,表明背景空区对该带大震具有中长期预报意义。最近一次背景空区业已形成,并出现与之配套的孕震空区,其演化图像符合强震孕育模式。研究发现,库玛断裂带中段M_L 3以上地震空区,对共和7级强震及周边200 km的强震有前兆意义。  相似文献   

基于间隙参数模型的盾构隧道周围土体位移分析   总被引：8，自引：3，他引：5  

杨冠天  项彦勇  张峰 《岩土力学》2005,26(10):1602-1606

基于一种盾构加载模型并引进间隙参数的概念,对盾构隧道周围土体位移的机理及预测方法进行了总结。盾构相对于设计轴线的偏移是影响土体变形的主要原因之一。确定间隙参数是应用解析方法的关键步骤,提出了一个半经验、半解析方法,并针对一个工程实例把现场测量值和理论计算值进行了对比分析。  相似文献   

A multi‐source precipitation estimation approach to fill gaps over a radar precipitation field: a case study in the Colorado River Basin          下载免费PDF全文

Kibrewossen B. Tesfagiorgis  Shayesteh E. Mahani 《水文研究》2015,29(1):29-42

The present work develops an approach to seamlessly blend satellite, available radar, climatological and gauge precipitation products to fill gaps in ground‐based radar precipitation field. To mix different precipitation products, the error of any of the products relative to each other should be removed. For bias correction, the study uses an ensemble‐based method that aims to estimate spatially varying multiplicative biases in SPEs using a radar precipitation product. A weighted successive correction method (SCM) is used to make the merging between error corrected satellite and radar precipitation estimates. In addition to SCM, we use a combination of SCM and Bayesian spatial model for merging the rain gauges (RGs) and climatological precipitation sources with radar and SPEs. We demonstrated the method using a satellite‐based hydro‐estimator; a radar‐based, stage‐II; a climatological product, Parameter‐elevation Regressions on Independent Slopes Model and a RG dataset for several rain events from 2006 to 2008 over an artificial gap in Oklahoma and a real radar gap in the Colorado River basin. Results show that: the SCM method in combination with the Bayesian spatial model produced a precipitation product in good agreement with independent measurements. The study implies that using the available radar pixels surrounding the gap area, RG, Parameter‐elevation Regressions on Independent Slopes Model and satellite products, a radar‐like product is achievable over radar gap areas that benefit the operational meteorology and hydrology community. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Spatiotemporal changes and correlation of the new urbanization and urban-rural income gap in Sichuan Province北大核心CSCD     

李靖  廖和平  刘愿理  张杰 《地理科学进展》2023,(4):657-669

新型城镇化作为健全区域协调发展体制机制的重要举措,对破解城乡及地区间发展不平衡问题、促进经济高质量发展有重要意义。论文以四川省为研究对象,运用空间自相关分析方法、空间计量模型、门限面板模型,分析2009—2019年新型城镇化和城乡收入差距的时空演化情况,揭示二者的关联关系,检验分析城乡收入差距的其他影响因素。结果显示：(1) 2009—2019年,四川省新型城镇化水平逐年上升,城乡收入差距逐年缩小,各年度城乡收入差距均具有显著的空间关联性,其低值区域主要集聚在成渝经济走廊上,其高值区域主要集聚在川西及东北部秦巴山区。(2)新型城镇化对城乡收入差距存在非线性影响,呈倒“U”型关系,主要原因是新型城镇化与农业现代化的不协调、不同步,当农业现代化水平跨越门槛值后,新型城镇化才会由扩大转为抑制城乡收入差距。(3)地区经济不平衡程度、科技创新水平和人力资本水平也是城乡收入差距的显著影响因素。研究结果可为积极稳妥推动新型城镇化、有效缩小城乡收入差距提供理论依据。  相似文献   

北祁连山-河西走廊大震危险区预测          下载免费PDF全文

邵延秀  袁道阳  曹娜  梁明剑 《地震地质》2011,(4):865-876

以青藏块体北部的北祁连山-河西走廊地震构造带为研究对象,在系统收集整理该区主干活动断裂新活动性特征、断裂滑动速率、历史地震及古地震资料的基础上,结合现今地震活动性,采用地震空区、空段识别方法和地震活动b值空间图像扫描方法,分析了研究区内历史地震及b值的分布特征.结果显示,该区的榆木山北缘断裂离逝时间较长,应力积累程度较...  相似文献   

Community Development Finance Institutions (CDFIs): Geographies of financial inclusion in the US and UK     

Lindsey Appleyard 《Geoforum》2011,42(2):250-258

The financial exclusion of enterprise is a concept that has been largely neglected by economic geographers. This is surprising given the attention dedicated to personal financial exclusion and alternative sources of finance. This paper compares financial inclusion policies in deprived areas of the United States (US) and United Kingdom (UK) through the example of Community Development Finance Institutions (CDFIs). CDFIs help overcome financial exclusion by providing local sources of loan finance to micro, small-and-medium-sized enterprises and social enterprises. Drawing upon interviews with key actors within the CDFI sector in the US and UK respectively, the paper aims to compare the CDFI landscape across the US and UK through the provision of finance for enterprise. This is in order to understand the geographies of finance that are being created by such alternative financial institutions thereby contributing to financial inclusion debates. The research concludes that although CDFIs do provide an important source of finance to excluded enterprises, policy initiatives have created uneven geographical coverage and market gaps leaving marked spaces of financial exclusion.  相似文献   

Prediction of wave-induced scour depth under submarine pipelines using machine learning approach     

A. Etemad-Shahidi  R. YasaM.H. Kazeminezhad 《Applied Ocean Research》2011,33(1):54-59

The scour around submarine pipelines may influence their stability; therefore scour prediction is a very important issue in submarine pipeline design. Several investigations have been conducted to develop a relationship between wave-induced scour depth under pipelines and the governing parameters. However, existing formulas do not always yield accurate results due to the complexity of the scour phenomenon. Recently, machine learning approaches such as Artificial Neural Networks (ANNs) have been used to increase the accuracy of the scour depth prediction. Nevertheless, they are not as transparent and easy to use as conventional formulas. In this study, the wave-induced scour was studied in both clear water and live bed conditions using the M5’ model tree as a novel soft computing method. The M5’ model is more transparent and can provide understandable formulas. To develop the models, several dimensionless parameter, such as gap to diameter ratio, Keulegan-Carpenter number and Shields number were used. The results show that the M5’ models increase the accuracy of the scour prediction and that the Shields number is very important in the clear water condition. Overall, the results illustrate that the developed formulas could serve as a valuable tool for the prediction of wave-induced scour depth under both live bed and clear water conditions.  相似文献   

海气通量涡相关法计算中的时间尺度分析     

黄艳松  宋金宝  范聪慧 《海洋科学》2011,35(11):114-119

基于黄海上连续14 d 的浮标观测资料, 采用多尺度分解法确定了海气通量涡相关法计算中的截断时间尺度, 并分析了该截断时间尺度的特征及其对感热通量计算的影响。研究结果是： 由多尺度分解法获得的湍通量截断时间尺度可将总通量中湍通量和中尺度通量分离开来, 截断时间尺度随着湍流强度或水平风速的增加而增加, 且感热通量的截断时...  相似文献   

Monazite–xenotime miscibility gap thermometry. I. An empirical calibration     

W. HEINRICH  G. REHS  & G. FRANZ 《Journal of Metamorphic Geology》1997,15(1):3-16

Rare earth element (REE) and yttrium concentrations of coexisting monazite and xenotime were determined from a suite of seven metapelites from the Variscan fold belt in NE Bavaria, Germany. The metapelites include a continuous prograde, mainly low-P (3–5 kbar) metamorphic profile from greenschist (c. 400 °C) to lower granulite facies conditions (c. 700 °C). The LREE (La–Sm) are incorporated preferentially in monoclinic monazite (REO₉ polyhedron), whereas the HREE plus Y are concentrated in tetragonal xenotime (REO₈ polyhedron). The major element concentrations of both phases in all rocks are very similar and do not depend on metamorphic grade. Monazite consists mainly of La, Ce and Nd (La_0.20–0.23, Ce_0.41–0.45, Nd_0.15–0.18)PO₄, all other elements are below 6 mol%. Likewise, xenotime consists mainly of YPO₄ with some Dy and Gd solid solutions (Y_0.76–0.80, Dy_0.05–0.07, Gd_0.04–0.06). In contrast, the minor HREE concentrations in monazite increase strongly with increasing metamorphic grade: Y, Dy and Gd increase by a factor of 3–5 from greenschist to granulite facies rocks. Monazite crystals often show zonation with cores low in HREE and rims high in HREE that is interpreted as growth zonation attained during prograde metamorphism. Similarly, Sm and Nd in xenotimes increase by a factor of 3–4 with increasing metamorphic grade. Prograde zonation in single crystals of xenotime was not observed. The X_HREE+Y in monazite and X_LREE in xenotime of the seven rocks define two limbs along the strongly asymmetric miscibility gap from c. 400 °C to 700 °C. The empirical calibration of the monazite miscibility gap limb coexisting with xenotime is appropriate for geothermometry. Due to its contents of U and Th, monazite has often been used for U–Pb age determination. The combination of our empirical thermometer on prograde zoned monazite along with possible age determination of zoned single crystals may provide information about prograde branches of temperature–time paths.  相似文献   

A polarimetric spectral imager using acousto-optic tunable filters     

WM. Hayden Smith  K. M. Smith 《Experimental Astronomy》1990,1(5):329-343

We report laboratory and telescopic observations with a polarimetric spectral imager based on an acousto-optic tunable filter (AOTF) where we demonstrate simultaneous acquisition of orthogonally polarized images at a spectral resolving power on the order of 103 and at a Rayleigh criterion spatial resolution of 100 line pairs per mm. This matches the spatial resolution of most digital arrays. An AOTF is shown to be usable as a fast shutter with a contrast of over 10⁴ on a sub-millisecond time scale while providing an high transmittance of about 75% (both polarizations summed) when illuminated by white light. The polarization contrast between the orthogonally polarized images exceeds 10⁴ across the field of view, permitting accurate measurement of the polarization parameters of incident light. These characteristics are now being used in a program of high spatial resolution imaging in narrow spectral bands. Some peculiarities and limitations of AOTFs are indicated.This research was supported by NASA under Grant NAGW-122 and under contract with the Jet Propulsion Laboratory under NASA grant NAS 7-918.Visiting Astronomer, Mauna Kea Observatory.  相似文献