Point Cumulative Semivariogram for Identification of Heterogeneities in Regional Seismicity of Turkey     

Zekai en 《Mathematical Geology》1998,30(7):767-787

Geological events are neither isotropic nor homogeneous in their occurrences. These two properties present difficulties for spatial modeling of regionalized variables. This paper presents a point cumulative semivariogram (PCSV) technique for quantifying the heterogeneity characteristics of the phenomenon concerned. The basis of the methodology is to obtain experimental PCSVs for each measurement point which led to estimation of radius of influence around each site. In addition, the experimental PCSVs provide basic information about the heterogeneity of the geological variable in the region, and furthermore many useful interpretations can be made concerning the regional variability of the variable. It provides the measure of cumulative similarity of a regional variable around any measurement site. Because PCSV is a means of measuring total similarity, maps at fixed similarity levels are provided in order to document the regional heterogeneity. Identification of heterogeneities depends on the comparison of fixed PCSV values at a multitude of irregularly scattered sites. The PCSV methodology has been applied to the regional seismic data of Turkey.  相似文献   

Numerical Method for Conditional Simulation of Levy Random Fields   总被引：2，自引：0，他引：2  

Scott Painter 《Mathematical Geology》1998,30(2):163-179

Stochastic simulations of subsurface heterogeneity require accurate statistical models for spatial fluctuations. Incremental values in subsurface properties were shown previously to be approximated accurately by Levy distributions in the center and in the start of the tails of the distribution. New simulation methods utilizing these observations have been developed. Multivariate Levy distributions are used to model the multipoint joint probability density. Explicit bounds on the simulated variables prevent nonphysical extreme values and introduce a cutoff in the tails of the distribution of increments. Long-range spatial dependence is introduced through off-diagonal terms in the Levy association matrix, which is decomposed to yield a maximum likelihood type estimate at unobserved locations. This procedure reduces to a known interpolation formula developed for Gaussian fractal fields in the situation of two control points. The conditional density is not univariate Levy and is not available in closed form, but can be constructed numerically. Sequential simulation algorithms utilizing the numerically constructed conditional density successfully reproduce the desired statistical properties in simulations.  相似文献   

Three-dimensional waveform sensitivity kernels   总被引：2，自引：0，他引：2  

Henk Marquering  Guust Nolet  & F.A. Dahlen 《Geophysical Journal International》1998,132(3):521-534

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Sensitivity of frequency-dependent traveltimes to laterally heterogeneous, anisotropic Earth structure     

Li Zhao  & Thomas H. Jordan 《Geophysical Journal International》1998,133(3):683-704

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Polarization anomaly of Love waves caused by lateral heterogeneity   总被引：1，自引：0，他引：1  

Reiji Kobayashi 《Geophysical Journal International》1998,135(3):893-897

We calculate surface waves propagating in a laterally heterogeneous structure beneath the Kuril trench, where significant Love-wave polarization anomalies, called quasi-Love waves, are generated. Since 3-D wave propagation in the two-dimensionally heterogeneous structure can be assumed, we apply the 2.5-D finite difference method to the surface-wave calculations. The calculations show that a velocity contrast of 7 per cent at depths of less than 210 km beneath the Kuril trench cannot generate quasi-Love waves, and that an unlikely contrast of 20 per cent is required to generate clear quasi-Love waves. The possible cause of the quasi-Love waves inferred from previous studies on coupled free oscillations is a lateral variation in azimuthal anisotropy. The lateral variation in azimuthal anisotropy beneath the Kuril trench suggests a change in the mantle flow induced by the subducting slab.  相似文献   

Water source characterization through spatiotemporal patterns of major,minor and trace element stream concentrations in a complex,mesoscale German catchment     

Holger L. Fröhlich  Lutz Breuer  Hans‐Georg Frede  Johan A. Huisman  Kellie B. Vaché 《水文研究》2008,22(12):2028-2043

The link between spatiotemporal patterns of stream water chemistry and catchment characteristics for the mesoscale Dill catchment (692 km²) in Germany is explored to assess the catchment scale controls on water quality and to characterize water sources. In order to record the spatiotemporal pattern, ‘snapshot sampling’ was applied during low, mean and high flow, including 73 nested sites throughout the catchment. Water samples were analysed for the elements Li, B, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Ba, Pb and U using inductively‐coupled‐plasma mass spectrometry, and for electric conductivity and pH. Principle component analysis and hierarchical cluster analysis were used to find typical element associations and to group water samples according to their hydrochemical fingerprints. This revealed regional hydrochemical patterns of water quality which were subsequently related to catchment attributes to draw conclusions about the controls on stream chemistry. It was found that various lithologic signals and anthropogenic point source inputs controlled the base flow hydrochemistry. During increased flows, stream waters were diluted causing additional hydrochemical variability in response to heterogeneous precipitation inputs and differences in aquifer storage capacities. The hydrochemical patterns further displayed in‐stream mixing of waters. This implied, that stream waters could be apportioned to the identified water sources throughout the catchment. The basin‐wide hydrochemical variability has the potential to outrange the tracer signatures typically inferred in studies at the hillslope scale and is able to strongly influence the complexity of the catchment output. Both have to be considered for further catchment scale tracer and modelling work. Despite the likelihood of non‐conservative behaviour, the minor and trace elements enhanced the rather qualitative discrimination of the various groundwater types, as the major cations were strongly masked by point source inputs. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Recovery of aspherical earth structure from observations of normal mode amplitudes     

F. F. Pollitz 《Geophysical Journal International》1990,102(2):313-339

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城市海量手机用户停留时空分异分析——以深圳市为例   总被引：1，自引：0，他引：1  

徐金垒  方志祥  萧世伦  尹淩 《地球信息科学学报》2015,(2):197-205

识别海量手机数据中蕴含的行为模式,是地理学的一个研究热点与难点。目前,较多研究针对手机用户移动特征开展,而对停留及其模式的研究则相对较少;其时空分异规律对理解城市人群动态,甚至优化城市系统至关重要。本文根据人们日常时空约束条件定义了手机用户停留,提出了基于海量手机位置数据的手机用户停留模式的提取方法,以深圳市约790万个匿名手机用户一天的海量手机位置数据为例,识别出了覆盖约98%用户的典型停留模式,并结合该城市土地利用的空间分布与分异特征,剖析不同停留模式的手机用户空间分异特征和城市不同区域停留次数的时段分异特征。研究发现:(1)15种停留模式可覆盖约98%的手机用户,而且其一天不同的停留位置数量不超过4个;(2)15种停留模式手机用户在城市区域空间上的分布存在分异现象,严重受制于土地利用的空间分布;(3)城市不同区域停留次数的时段分异特征与该区域常住人口、人口密度,以及区域主要职能和性质存在较强的相关性。研究结论对理解城市手机用户行为模式的群体特征有积极的意义,对城市土地利用的科学决策和城市交通规划与预测有重要参考价值。  相似文献   

地形因子与小微地震相关度的空间异质性分析     

黄泽纯  刘子璞  于东雷  张倩宁 《测绘与空间地理信息》2021,44(4):1-4

针对传统最小二乘回归未能顾及数据的空间特性,且无法度量模型自变量与因变量相关性的空间变异特性的问题,本文提出利用地理加权回归方法分析小微地震频次与地形因子相关度的空间异质性。以四川地区的地震监测资料、DEM为实验数据,选取地形复杂度、坡度变率、坡向变率和地面曲率为自变量,地震发生频次为因变量,构建地理加权回归模型,并进行回归系数的空间变异分析。实验分析发现,地震频次与地形因子具有一定的相关性:地形复杂度与地震频次相关性最强;坡度变率、沟壑密度、剖面曲率与地震频次的相关性依次减弱;不同空间位置的地形因子和地震频次的相关性具有较明显的空间异质性。实验结果表明,地理加权回归可以有效地度量分析地震频次与地形因子相关度的空间异质性,研究结果可为地震及次生灾害的分析与预报提供辅助决策参考。  相似文献   

陆面过程模型中垂直非均匀土壤的水分传输及相变的模拟   总被引：1，自引：0，他引：1  

李倩  孙菽芬 《大气科学》2015,39(4):827-838

土壤湿度在陆气相互作用中的重要性体现在它既能影响陆地和大气之间水循环的速率, 又能改变地表的能量分配。本文针对陆面过程模型中描述土壤湿度变化的方程进行了理论分析, 指出在非均匀土壤和冻土中采用土壤水势梯度描述垂直非均匀土壤水分流动的合理性。基于描述土壤内部水热传输的统一土壤模型, 并利用推广的表征土壤水分特征的Clapp-Hornberger关系式, 研究了非冻结和冻结的土壤湿度对于垂直非均匀土壤的敏感性。结果表明, 由土壤质地决定的土壤水势和导水率对土壤湿度的模拟有重要的影响。具体地, 在决定土壤性质的Clapp-Hornberger关系式中, 与土壤质地有关的饱和水势、饱和导水率以及土壤孔隙大小分布指数B, 对土壤湿度的模拟起到了关键作用。参数B的重要性尤为突出, 它的增加会引起导水率的大大下降, 从而对水分在土壤中的垂直分布产生重要影响。饱和水势的绝对值和参数B的增加会使得土壤水势绝对值增加明显, 使土壤的结冰(融化)过程延迟, 土壤温度因为没有结冰(融化)释放(吸收)的潜热加热(冷却)而持续下降(上升), 因此在冻融时期土壤温度会比观测值振幅偏大。上述结果揭示了考虑土壤垂直非均匀性并采用有效的土壤特性参数对于陆面过程模型的重要性。  相似文献