基于Love波相速度反演南北地震带地壳上地幔结构   总被引：5，自引：3，他引：2       下载免费PDF全文

徐小明  丁志峰  叶庆东  吕苗苗 《地球物理学报》2015,58(11):3928-3940

收集了南北地震带区域地震台网中292个地震台站2008年1月至2011年3月期间的地震波形数据,由频时分析方法提取了Love波相速度频散曲线,经过反演得到了研究区内的Love波相速度分布.根据Love波纯路径频散,采用线性反演方法对0.25°×0.25°的网格点进行了一维S波速度结构反演,利用线性插值获取了南北地震带地区的三维S波速度结构.结果显示了松潘—甘孜地体和川滇菱形块体地区的下地壳具有明显的S波低速层分布,该异常分布特征支持解释青藏高原隆升及其地壳物质运移的下地壳流模型.在100至120km深度上,川滇菱形块体西北部呈现较强的S波高速异常,这可能是印度岩石圈板块沿喜马拉雅东构造结下插至该区域所致,该区域下地壳的低速软弱物质与上地幔的高速强硬物质形成了鲜明对比,暗示了地壳和上地幔可能具有不同的构造运动和变形方式,这为该区域的壳幔动力学解耦提供了条件.  相似文献   

Evaluation of the "time factor" and "light factor" methods for estimating daily phytoplankton production at the sea surface     

《African Journal of Marine Science》2013,35(1):139-143

Daily phytoplankton production was estimated at the sea surface in the southern Benguela Current during January, March, April and October 1978 by different methods of calculation. Actual daily production (P_{24 meas}) was obtained from a series of short-term (3—4 h) incubations spanning 24 hours. Daily production was also extrapolated from single measurements during daylight by the "time factor" and "light factor" methods of calculation. These estimates (P_{24 calc}) vary considerably from P_{24 meas}, but on average they underestimate daily production. Estimates by the "light factor" method are generally lower and more variable than those from the "time factor" method. Differences in amplitude and timing of fluctuations in the rate of net production during daylight make it impossible to calculate reliable factors for correcting diel variations in photosynthesis when estimating daily production from short-term measurements. It is suggested that the effects of diel variation in production are likely to be less significant in the euphotic zone as a whole than at the sea surface alone.  相似文献   

基于三角模糊数随机模拟的地下水环境系统综合风险评价模型   总被引：3，自引：1，他引：2  

金菊良  刘丽  汪明武  李如忠  周玉良 《地理科学》2011,31(2):143-147

采用随机模拟方法模拟三角模糊数,把三角模糊数及函数间运算简化为普通的实数之间运算,建立基于三角模糊数随机模拟的地下水环境系统综合风险评价模型(ARA-SSTFN)。结果说明:以置信区间形式表示的ARA-SSTFN评价结果,比现有常规方法结果提供评价结果可靠性方面更多信息,能反映受多种不确定性因素综合影响的地下水环境系统综合风险评价客观实际情况;ARA-SSTFN在流域水资源、水环境和水旱灾害等有随机性、模糊性和数据资料不精确等多种不确定性因素综合作用的各种资源环境系统综合风险评价问题中有推广应用价值。  相似文献   

Applying local Green's functions to study the influence of the crustal structure on hydrological loading displacements     

《Journal of Geodynamics》2015

The influence of the elastic Earth properties on seasonal or shorter periodic surface deformations due to atmospheric surface pressure and terrestrial water storage variations is usually modeled by applying a local half-space model or an one dimensional spherical Earth model like PREM from which a unique set of elastic load Love numbers, or alternatively, elastic Green's functions are derived. The first model is valid only if load and observer almost coincide, the second model considers only the response of an average Earth structure. However, for surface loads with horizontal scales less than 2500 km², as for instance, for strong localized hydrological signals associated with heavy precipitation events and river floods, the Earth elastic response becomes very sensitive to inhomogeneities in the Earth crustal structure.We derive a set of local Green's functions defined globally on a 1° × 1° grid for the 3-layer crustal structure TEA12. Local Green's functions show standard deviations of ±12% in the vertical and ±21% in the horizontal directions for distances in the range from 0.1° to 0.5°. By means of Green's function scatter plots, we analyze the dependence of the load response to various crustal rocks and layer thicknesses. The application of local Green's functions instead of a mean global Green's function introduces a variability of 0.5–1.0 mm into the hydrological loading displacements, both in vertical and in horizontal directions. Maximum changes due to the local crustal structures are from −25% to +26% in the vertical and −91% to +55% in the horizontal displacements. In addition, the horizontal displacement can change its direction significantly. The lateral deviations in surface deformation due to local crustal elastic properties are found to be much larger than the differences between various commonly used one-dimensional Earth models.  相似文献   

Love wave tomography in Italy from seismic ambient noise          下载免费PDF全文

Hongyi Li  Fabrizio Bernardi  Alberto Michelini 《地震科学（英文版）》2010,23(5):487-495

We estimate Love wave empirical Green's functions from cross-correlations of ambient seismic noise to study the crust and uppermost mantle structure in Italy.Transverse-component ambient noise data from October 2005 through March 2007 recorded at 114 seismic stations from the Istituto Nazionale di Geofisica e Vulcanologia (INGV) national broadband network,the Mediterranean Very Broadband Seismographic Network (MedNet) and the Austrian Central Institute for Meteorology and Geodynamics (ZAMG) yield more than 2 000 Love wave group velocity measurements using the multiple-filter analysis technique.In the short period band (5-20 s),the cross-correlations show clearly one-sided asymmetric feature due to non-uniform noise distribution and high local activities,and in the long period band (20 s) this feature becomes weak owing to more diffusive noise distribution.Based on these measurements,Love wave group velocity dispersion maps in the 8-34 s period band are constructed,then the SH wave velocity structures from the Love wave dispersions are inverted.The final results obtained from Love wave data are overall in good agreement with those from Rayleigh waves.Both Love and Rayleigh wave inversions all reveal that the Po plain basin is resolved with low velocity at shallow depth,and the Tyrrhenian sea is characterized with higher velocity below 8 km due to its thin oceanic crust.  相似文献   

Zn上的k次不可约多项式与k阶Carmichael数     

覃仕霞 《成都信息工程学院学报》2010,25(5):557-560

设n是合数,如果对一切f（x）∈Zn[x]都满足f（x）nk≡f（x）mod（n,r（x））,那么就称n是模r（x）的k阶Carmichael数,这里r（x）是Zn[x]上的k次首一不可约多项式,用Ck,r（x）表示所有这种数的集合,并且定义Ck=Ur（x）Ck,r（x）.k阶Carmichael数,当k=4时,已证明了n=pq,p,q是不同的奇素数,p2-1,q3-1均整除n4-1,则n∈C4.主要目的是将k=4时得出的结论推广到k≥4的一般情形,利用孙子定理,通过构造Zn上的首一k次不可约多项式f（x）的方法,得出：在k≥4时,设n=pq,如果k=2m,m≥2,pm-1,q2m-1-1均整除nk-1,则n∈Ck;如果k=2m＋1,m≥2,pm-1,pm＋1-1,q2m-1均整除nk-1,则n∈Ck.  相似文献   

基于卫星服务中断的GPS在中国服务区可用性分析     

李国重  李军正  李建文  归庆明 《测绘学院学报》2011,(1)

由于导航卫星硬件失效和轨道维持等原因,会引起卫星服务的暂时中断。卫星服务中断又会导致导航星座可用性下降。以GPS卫星4类中断的平均间隔时间、平均恢复时间为参数,建立了导航卫星的平均可用性及导航星座平均可用性数学模型。仿真分析了卫星服务中断的情况下GPS在我国服务区的可用性。仿真结果对于我国目前进行的区域卫星导航系统建设(北斗卫星导航系统建设的第2步)以及参与GPS市场竞争均具有重要作用。  相似文献   

f_oF₂月中值太阳循环变化及单站谱模型研究   总被引：1，自引：0，他引：1       下载免费PDF全文

徐彤  吴振森  吴健  黄朝军  冯健 《地球物理学报》2008,51(5):1296-1303

利用我国9个电离层观测站第21和22太阳周大约20年的f_oF₂月中值数据,分析太阳活动和地磁活动对电离层f_oF₂的影响,结果显示白天和夏季夜间f_oF₂和太阳黑子数R之间存在着明显非线性关系,并且随着纬度的降低逐渐增强．当回归分析加入地磁Ap指数时,多重回归模型与实测值误差进一步减小,说明同时考虑太阳活动和地磁活动的非线性影响能够更好地描述f_oF₂的变化．基于f_oF₂太阳黑子数R及地磁指数Ap之间的非线性统计关系,利用Fourier 级数建立9个单站谱模型,并与国际参考电离层IRI进行了比较,精度有一定提高．  相似文献   

利用地脉动台阵记录反演场地浅层Vs结构     

董连成  陶夏新  师黎静  李广影 《岩土力学》2008,29(2):553-556

比较了影响Love波相速度频散曲线的主要因素,通过虚拟反演,说明了利用Love波相速度反演浅层剪切波速度结构的可行性,以地脉动台阵3分量观测记录提取的Love波相速度频散曲线为目标函数,利用遗传算法与单纯形法混合算法,分两种情况反演了某实际工程场地的浅层剪切波速度结构。结果表明,利用从地脉动台阵3分量观测资料中提取的Love波相速度反演工程场地浅层的剪切波速度Vs结构是一种很有前景的技术方法。  相似文献   

Love Numbers And Elastic Energy Of Deformation For Venus     

Xia  Y.F.  Xiao  N.Y. 《Earth, Moon, and Planets》2000,88(2):75-87

Love numbers of second order of Venus are calculated with resolving fundamental differential equations of elastic body according to the parameters of the density and the elasticity of material by means of the PVM94-01 Venus model. Meanwhile, the elastic energy of deformation of second order due to the tidal perturbation of the Sun and that due to rotational centrifugal potential are also calculated. The values of Love number provide a basis for model of internal structure of Venus. The numerical calculation of the elastic energy of deformation gives a magnitude evaluation of the perturbation terms to the Hamiltonian expressions in the study of dynamics of the elastic Venus. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献