Coseismic deformation and slip distribution of the 1997 7.5 Manyi, Tibet, earthquake from InSAR measurements     

Hua Wang  Caijun Xu  Linlin Ge 《Journal of Geodynamics》2007,44(3-5):200-212

We use interferometric synthetic aperture radar (InSAR) observations to investigate the coseismic deformation and slip distribution of the 1997 M_w7.5 Manyi earthquake, a left-lateral strike-slip earthquake occurred on the west portion of the Kunlun fault in the northern Tibet, China. The fault trace is constrained by the combination of interferometric coherence image and azimuth offset image. The total length of the identified fault is about 170 km. We estimate the source parameters using a seven-segment fault model in a homogeneous elastic half-space. We first use a uniform slip model to estimate the slip, width, dip and rake for each segment, resulting in a maximum slip of 5.5 m with a depth of 11 km on the fourth segment. The average dip of the uniform slip model is about 93° northward and the average rake is about −2°. We then use a distributed slip model to estimate the pure strike-slip and oblique slip distribution, respectively. In the distributed slip model, the fault plane is discretized into 225 patches, each of them 4 km × 4 km. We fix the optimal geometric parameters and solve for the slip distribution using a bounded variable least-squares (BVLS) method. We find a geodetic moment of 1.91 × 10²⁰ Nm (M_w7.5), of which almost 68% released in the uppermost 8 km and 82% in the uppermost 12 km. For all the models used in this study, the synthetic profiles along strike show asymmetric displacements on the opposite sides of the fault, which are in agreement with the observations. This suggests that a linear elastic model with variable and non-vertical dips is also reasonable for the mechanism of the Manyi earthquake.  相似文献   

近50年庐山气温和降水变化趋势分析     

刘文英  王保生 《气象与减灾研究》2007,30(4):43-46,F0002

利用庐山气象站逐月观测资料,对1956—2005年庐山气温和降水的变化趋势进行了分析。结果表明,近50 a庐山年平均气温上升了0.8℃,其中冬季上升最明显,为1.5℃;夏季呈下降趋势,为0.2℃。20世纪60年代庐山年平均气温、夏季最高气温下降最为明显,1996年以后上升最为明显。年降水量自1996年起明显下降。庐山的年最高气温、年最低气温、秋季平均气温、秋季最高气温、春季最高气温、春季最低气温在1998年发生了均值突变,冬季最低气温则在1992年前后出现了均值突变;夏季降水在1995年出现均值突变。  相似文献   

一种基于知识的航空影像中道路半自动提取方法     

马永刚  张占睦 《测绘科学技术学报》2000,17(1):34-37

利用线特征算子和多种线状地物跟踪方法建立了一种基于知识的航空影像中道路半自动提取方法。该算法计算量小,判断速度快,准确率较高,并且有较好的适应性。试验表明这是一种良好的道路提取方法。  相似文献   

Baroclinic Instability in the Generalized Phillips' Model Part Ⅱ:Three-layer Model     

李扬 《大气科学进展》2000,(3)

1.IntroductionBaroclinicinstabilityistheprocessbywhichtheavailablepotentialenergyofarotatingstratifiedfluidmaybeconvertedintothekineticenergyofagrowingdisturbance.Throughthegenerationofeddiesandthesubsequentinteractionbetweentheseeddiesandthemeanflow,baroclinicinstabilityisanimportantfeatureofthedynamicsoflarge-scalegeophysicalsystems.Thefirstcompletetheoreticalexplanationsofthephenomenonweregivenindepen-dentlybyCharney(l947)andEady(l949),whousedsimplemodelstoexplainthelarge-scalewavesobserve…  相似文献   

地震层析成像反演中解的定量评价及其应用   总被引：11，自引：4，他引：7       下载免费PDF全文

刘伊克  常旭 《地球物理学报》2000,43(2):251-256

对地震层析成像非线性问题线性化处理之后,各种反演算法归纳成为对不适定方 程的求解．地震层析成像反演算法的解的物理意义是给出地质结构,因此对于解的可靠性及 分辨率研究非常重要．然而许多反演算法不能给出解的评价方法,因而对解的可信度产生怀 疑．本研究根据解估计的分辨率矩阵的原理,提出ＬＳＱＲ（Ｌｅａｓｔ Ｓｑｕａｒｅ ＱＲ）算法解协方差矩 阵的评价算法,用相关分析可以为那些在求解过程中得不到分辨率矩阵的反演方法提供解的 定量评价．并用本文提出的解的定量评价方法试评了一个实际地壳模型的地震层析成像的 速度重建结果．  相似文献   

Regionality in Norwegian farmland abandonment: Inferences from production data     

《Applied geography (Sevenoaks, England)》2014

Economic subsidies continue to be in focus as potentially important drivers of agricultural change. Their exact functioning as drivers in very complex systems are not all that well analysed or documented however, and their effect e.g. in terms of environmental output are currently being questioned. In the work reported here, we focus on how the regionality of the farming system may influence the potential effect of agricultural subsidies, also in terms of farmland abandonment. We do this through using multiple linear regressions (MLR) and geographically weighted regression (GWR) on the Norwegian database on agricultural production data, combined with farm location data. Our findings demonstrate how the outcome of certain support systems may differ between regions, and how a region may dominate national statistic. We conclude that as subsidies continue to be a key tool in achieving agricultural policy aims, we need a better understanding of how the subsidy systems work. To understand the impact of a change in subsidy it is necessary to consider the local context in which it operates, e.g. demographics, bio-physical resources and feasibility of land rental. Spatial data and techniques such as spatial MLR and GWR are increasingly accessible to policy makers and should be used to provide insight into the local impacts of current policy. However this understanding must also emphasize farmer motivation and decision making and these investigations must be regionally based.  相似文献   

蒙自地区蒸发折算系数分析     

郑皎  王继红  李华伟 《辽宁气象》2011,(1):45-47

利用始于1953年的蒙自气候站小型蒸发器和始于1986年的E-601B型蒸发器蒸发量观测资料,计算两种蒸发器蒸发量折算系数,并与相关分析及线性拟合的结果进行对比分析。结果表明：蒙自站小型蒸发器与E-601B型蒸发器蒸发量的时程分配基本一致,两者之间具有较好的相关关系,线性拟合的线性系数与折算系数较为一致,且检验结果较为接近,推算出该地区两种仪器年蒸发量的折算系数为0.65。研究结果可用于本区气候评价、水量平衡分析和水资源调查等。  相似文献   

The effect of dispersion on the stability of density-driven flows in saturated homogeneous porous media     

Jude L. Musuuza  Florin A. Radu  Sabine Attinger 《Advances in water resources》2011,34(3):417-432

This work is a continuation of Musuuza et al. [37] in which a stability criterion for density-driven flow in a saturated homogeneous medium was derived. The criterion predicted the stability of a system as a function of the density and viscosity contrasts, the magnitude of the flow velocity and the concentration gradients for flow aligned orthogonal to gravity. It could not accurately predict stability transition with increasing velocity, a failure we attributed to dispersion effects that were not included. Small-scale dispersion and molecular diffusion, the main stabilising mechanisms in homogeneous media can stabilise flow if the instability wavelengths are below a certain cutoff. The width of the mixing zone is also central in controlling the range of wavelengths that persist into fingers. We propose a method of quantifying the cutoff wavelength and the width of the mixing zone, which are incorporated into the earlier criterion as constituents of the dispersive part. The earlier criterion is reformulated in terms of the Rayleigh number and with the dispersive part added, we attempt to predict the number of fingers formed which is directly related to the physical stability of the system. The inclusion of the Rayleigh number and dispersion into a single stability criterion provides new insight in the way dispersion affects vertical flow systems. Stability numbers computed with the new criterion are in reasonable agreement with numerical simulations for a range of physical variables. The numerical computations are performed with the software package d³f, which uses the cell-centred finite volume and the implicit Euler methods for the spatial and temporal discretisations, respectively. The admission of the density and dispersivities as inputs into the criterion makes it usable in practical problems.  相似文献   

The stability of density-driven flows in saturated heterogeneous porous media     

Jude L. Musuuza  Florin A. Radu  Sabine Attinger 《Advances in water resources》2011,34(11):1464-1482

This work concludes the investigations into the stability of haline flows in saturated porous media. In the first part [33] a stability criterion for density-driven flow in a saturated homogeneous medium was derived excluding dispersion. In the second part [34], the effects of dispersion were included. The latter criterion made reasonable predictions of the stability regimes (indicated by the number of fingers present) as a function of density and dispersivity variations. We found out that destabilising variables caused an increase in the number of fingers and vice versa. The investigation is extended here for the effects of the medium heterogeneity. The cell problem derived via homogenization theory [20] is solved and its solution used to evaluate the elements of the macrodispersion tensor as functions of time for flow aligned parallel to gravity. The longitudinal coefficient exhibits asymptotic behaviour for favourable and moderately unfavourable density contrasts while it grows indefinitely for higher density contrasts. The range of densities stabilised by medium heterogeneities can thus be estimated from the behaviour of the coefficient. The d³f software program is used for the numerical simulations. The code uses the cell-centred finite volume and the implicit Euler techniques for the spatial and temporal discretisations respectively.  相似文献   

Adsorption Kinetic Modeling of Safranin onto Rice Husk Biomatrix Using Pseudo‐first‐ and Pseudo‐second‐order Kinetic Models: Comparison of Linear and Non‐linear Methods     

Shamik Chowdhury  Papita Saha 《洁净——土壤、空气、水》2011,39(3):274-282

Batch kinetic studies were carried out for the removal of safranin from aqueous solution using a biomatrix prepared from rice husk. The adsorption kinetic data were modeled using the pseudo‐first‐order and pseudo‐second‐order kinetic equations. The linear and non‐linear forms of these two widely used kinetic models were compared in this study. In order to determine the best‐fitting equation, the coefficient of determination (r²), the sum of the squares of the errors (SSE), sum of the absolute errors (SAE), average relative error (ARE), hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), and the Chi‐squared test (χ²) were used as error analysis methods. Results showed that the non‐linear forms of pseudo‐first‐order and pseudo‐second‐order models were more suitable than the linear forms for fitting the experimental data. Non‐linear method is thus more appropriate for estimating the kinetic parameters and should primarily be used to describe adsorption kinetics.  相似文献