Moment tensor of the 1999 Dead Sea calibration shot: limitations in the isotropic source retrieval without a detailed earth model     

J. Sileny  R. Hofstetter 《Tectonophysics》2002,356(1-3)

Records of the November 11, 1999, M_L=3.9 calibration shot observed at three broad-band (BB) stations at a distance range from 35 to 63 km from the epicenter were inverted with a simple 1-D model. Complexity due to the water–solid bedrock interface near the hypocenter effectively masks the explosive mechanism in first-motion polarities. Reverberation in the water and scattering in the crust result in the long duration of the source process if estimated with a simple structure model. Only the part with a significant non-zero isotropic (ISO) component should be considered. We selected this part on the basis of the estimate of error due to inexact modeling of the crust constructed by perturbing the thickness and velocities in individual layers by 5% of their current values. Within this interval, the isotropic process of explosive characteristics is detected. However, if we do not check the significance of the isotropic part in the formally reconstructed source process, then we might miss the information about the explosion and arrive with a spurious nearly double-couple source.  相似文献   

FY-1C遥感器可见近红外各通道在轨辐射定标   总被引：13，自引：0，他引：13  

张玉香  张广顺  黄意玢  邱康睦  胡秀清  戎志国  王维和  刘志权  张立军  朱舜斌  王永宽  李昌宝  夏青  陈秀莲  方宗义 《气象学报》2002,60(6):740-747

文中通过 1999年 7月利用敦煌辐射定标场和反射率基法对FY -1C气象卫星遥感器可见 -近红外通道进行的第一次在轨辐射定标试验 ,研究和试验了卫星遥感器的在轨辐射定标方法、同步观测方法和辐射传输计算算法及其软件开发 ,有 7个通道的绝对辐射定标系数 (或称为增益和偏离量 )被获得。经过误差分析 ,认为本次定标的不确定度小于 7%。定标获得的 7个通道定标系数与该卫星发射前定标结果比较 ,其中 5个通道 (通道 1,2 ,7,8,10 )结果比较接近 ,另两个通道 (通道 6,9)由于发射前定标误差较大致使二者有一定差别。另外 ,通过 2 0 0 0年 9月份对FY -1C卫星进行的第二次辐射定标试验 ,使该卫星在轨 1a多来的运行状态得到了定量监测 ,本次定标与1999年 7月的定标结果比较 ,发现可见 -近红外各通道性能均有程度不同的衰减 ,尤其是通道 1,7,8性能衰减分别为 35% ,2 8% ,2 2 % ,而通道 2 ,6,9,10性能衰减较小 (为 10 %左右 )。  相似文献   

A hybrid genetic—instance based learning algorithm for CE-QUAL-W2 calibration     

Avi Ostfeld  Shani Salomons   《Journal of Hydrology》2005,310(1-4):122-142

This paper presents a calibration model for CE-QUAL-W2. CE-QUAL-W2 is a two-dimensional (2D) longitudinal/vertical hydrodynamic and water quality model for surface water bodies, modeling eutrophication processes such as temperature–nutrient–algae–dissolved oxygen–organic matter and sediment relationships. The proposed methodology is a combination of a ‘hurdle-race’ and a hybrid Genetic-k-Nearest Neighbor algorithm (GA-kNN). The ‘hurdle race’ is formulated for accepting–rejecting a proposed set of parameters during a CE-QUAL-W2 simulation; the k-Nearest Neighbor algorithm (kNN)—for approximating the objective function response surface; and the Genetic Algorithm (GA)—for linking both. The proposed methodology overcomes the high, non-applicable, computational efforts required if a conventional calibration search technique was used, while retaining the quality of the final calibration results. Base runs and sensitivity analysis are demonstrated on two example applications: a synthetic hypothetical example calibrated for temperature, serving for tuning the GA-kNN parameters; and the Lower Columbia Slough case study in Oregon US calibrated for temperature and dissolved oxygen. The GA-kNN algorithm was found to be robust and reliable, producing similar results to those of a pure GA, while reducing running times and computational efforts significantly, and adding additional insights and flexibilities to the calibration process.  相似文献   

山西测震台网地震计工作状态检测及故障原因分析     

刘林飞  宫卓宏  梁向军  殷伟伟  高云峰 《山西地震》2021,(1):38-41

以山西省测震台网部分台站使用的地震计为研究对象,选取一段时间的脉冲标定波形数据进行计算,根据脉冲标定处理结果分析得出地震计工作周期和阻尼变化的特点及原因,结合测震台网运行与维护实际工作经验,提出了检测地震计工作状态的思路和方法。实践证明,采用定期检测地震记周期和阻尼的变化可以在一定程度上反映出测震台站地震计运行的工作状态。  相似文献   

用标定方法检测地震计的异常状态     

张明  俞铁宏  刘洋君  李俊 《山西地震》2014,(3):34-37

以浙江省测震台网部分台站地震计为研究对象,选取一定时间窗口对阶跃标定波形进行计算,得出地震计在该时段内的周期和阻尼变化情况。结合台网台站运行维护工作,经过统计分析,表明利用此方法能够在一定程度上反映出台站地震计运行的异常状态。  相似文献   

Constraining water table depth simulations in a land surface model using estimated baseflow     

Min-Hui Lo  Pat J.-F. Yeh  J.S. Famiglietti   《Advances in water resources》2008,31(12):1552-1564

Several recent studies have shown the significance of representing groundwater in land surface hydrologic simulations. However, optimal methods for model parameter calibration in order to realistically simulate baseflow and groundwater depth have received little attention. Most studies still use globally constant groundwater parameters due to the lack of available datasets for calibration. Moreover, when models are calibrated, various parameter combinations are found to exhibit equifinality in simulated total runoff due to model parameter interactions. In this study, a simple lumped groundwater model is incorporated into the Community Land Model (CLM), in which the water table is interactively coupled to soil moisture through the groundwater recharge fluxes. The coupled model (CLMGW) is successfully validated in Illinois using a 22-year (1984–2005) monthly observational dataset. Baseflow estimates from the digital recursive filter technique are used to calibrate the CLMGW parameters. The advantage obtained from incorporating baseflow calibration in addition to traditional calibration based on measured streamflow alone is demonstrated by a Monte Carlo-type simulation analysis. Using the optimal parameter sets identified from baseflow calibration, flow partitioning and water table depth simulations using CLMGW are improved, and the equifinality problem is alleviated. For other regions that lack observations of water table depth, the baseflow calibration approach can be used to enhance parameter estimation and constrain water table depth simulations.  相似文献   

Calibration of subsurface batch and reactive-transport models involving complex biogeochemical processes     

L. Shawn Matott  Alan J. Rabideau 《Advances in water resources》2008

In this study, the calibration of subsurface batch and reactive-transport models involving complex biogeochemical processes was systematically evaluated. Two hypothetical nitrate biodegradation scenarios were developed and simulated in numerical experiments to evaluate the performance of three calibration search procedures: a multi-start non-linear regression algorithm (i.e. multi-start Levenberg–Marquardt), a global search heuristic (i.e. particle swarm optimization), and a hybrid algorithm that combines the particle swarm procedure with a regression-based “polishing” step. Graphical analysis of the selected calibration problems revealed heterogeneous regions of extreme parameter sensitivity and insensitivity along with abundant numbers of local minima. These characteristics hindered the performance of the multi-start non-linear regression technique, which was generally the least effective of the considered algorithms. In most cases, the global search and hybrid methods were capable of producing improved model fits at comparable computational expense. In other cases, the multi-start and hybrid calibration algorithms yielded comparable fitness values but markedly differing parameter estimates and associated uncertainty measures.  相似文献   

Incorporating multiple observations for distributed hydrologic model calibration: An approach using a multi-objective evolutionary algorithm and clustering     

Soon-Thiam Khu  Henrik Madsen  Francesco di Pierro 《Advances in water resources》2008

The use of distributed data for model calibration is becoming more popular in the advent of the availability of spatially distributed observations. Hydrological model calibration has traditionally been carried out using single objective optimisation and only recently has been extended to a multi-objective optimisation domain. By formulating the calibration problem with several objectives, each objective relating to a set of observations, the parameter sets can be constrained more effectively. However, many previous multi-objective calibration studies do not consider individual observations or catchment responses separately, but instead utilises some form of aggregation of objectives. This paper proposes a multi-objective calibration approach that can efficiently handle many objectives using both clustering and preference ordered ranking. The algorithm is applied to calibrate the MIKE SHE distributed hydrologic model and tested on the Karup catchment in Denmark. The results indicate that the preferred solutions selected using the proposed algorithm are good compromise solutions and the parameter values are well defined. Clustering with Kohonen mapping was able to reduce the number of objective functions from 18 to 5. Calibration using the standard deviation of groundwater level residuals enabled us to identify a group of wells that may not be simulated properly, thus highlighting potential problems with the model parameterisation.  相似文献   

Numerical modelling of the suspended sediment transport in Torres Strait     

N. Margvelashvili  F. Saint-Cast  S. Condie 《Continental Shelf Research》2008

One-dimensional vertical and three-dimensional fine-resolution numerical models of sediment transport have been developed and applied to the Torres Strait region of northern Australia. The one-dimensional model, driven by measured waves and currents, was calibrated against measured suspended sediment concentrations using a sequential data assimilation algorithm. The algorithm produced a good match between model and data, but this was achieved only by allowing some temporal variability in parameter values, suggesting that there were underlying uncertainties in the model structure and forcing data. Implications of the assimilation results to the accuracy of the numerical modelling are discussed and the need for observational programmes having an extensive spatial and temporal coverage is highlighted. The three-dimensional sediment model, driven by modelled waves and currents, simulates sediment transport over the shelf during the monsoon and trade-wind seasons covering 1997–2000. The model predicts strong seasonal variability of the sediment transport on the shelf attributed to seasonally varying hydrodynamics, and illustrates significant inter-annual variability of the sediment fluxes driven by extreme events. The developed model provides a platform for testing scientific hypothesis. With additional calibration, including uncertainty analysis, it can also be used in a management context.  相似文献   

A method for spatial calibration of wave hindcast data bases     

Antonio Tomas  Fernando J. Mendez  Inigo J. Losada 《Continental Shelf Research》2008

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