The K Method for Estimating Earthquake Activity Parameters and Effect of the Boundary Uncertainty of the Source Region:Discussion on the Seismic Zoning Method

Two aspects of a new method,which can be used for seismic zoning,are introduced in this paper.On the one hand,the approach to estimate b value and annual activity rate proposed by Kijko and Sellevoll needs to use the earthquake catalogue.The existing earthquake catalogue contains both historical and recent instrumental data sets and it is inadequate to use only one part.Combining the large number of historical events with recent complete records and taking the magnitude uncertainty into account,Kijko’s method gives the maximum likelihood estimation of b value and annual activity rate,which might be more realistic.On the other hand,this method considers the source zone boundary uncertainty in seismic hazard analysis,which means the earthquake activity rate across a boundary of a source zone changes smoothly instead of abruptly and avoids too large a gradient in the calculated results.

Parameter regionalization of the FLEX-Global hydrological model

Global hydrological models(GHMs) are important tools for addressing worldwide change-related water resource problems from a global perspective. However, the development of these models has long been hindered by their low accuracy. In order to improve the streamflow simulation accuracy of GHMs, we developed a GHM—the FLEX-Global—based on the regionalization of hydrological model parameters. The FLEX-Global model is primarily based on the framework of the FLEX hydrological model coupled with the HAND-based Storage Capacity curve(HSC) runoff generation module to calculate net rainfall, and uses the global river-routing Ca Ma-Flood model to calculate river network routing. This new model allows for streamflow simulation at a spatial resolution of 0.5°×0.5° and a temporal resolution of 1 day in global catchments. To validate FLEX-Global accuracy, the FLEX-Global-simulated streamflow of 26 major rivers distributed in five different climate zones was compared with the observed data from the Global Runoff Data Center(GRDC). Next, the model performance of FLEXGlobal was further verified by comparing it with that of seven existing GHMs with varying accuracy in the five climate zones.Multi-metric evaluation indicated that the streamflow simulation accuracy was improved by the FLEX-Global model with regionalized parameters, especially in the tropical and dry climate zones. This newly-developed GHM with regionalized parameters can provide scientific support for the assessment of climate change impact, optimization of global water resource mangement, simulation of Earth's multi-sphere coupling, and implementation of the Inter-Sectoral Impact Model Intercomparison Project(ISIMIP).

Comparison of three regionalization techniques for predicting streamflow in ungaged watersheds in Nebraska,USA using SWAT model

This study compared three approaches,regional averaging,nearest neighbor,and donor techniques,to regionalize parameters in the Soil and Water Assessment Tool(SWAT)on eleven watersheds located in the Dissected Plains,Plains,and Rolling Hills Landforms in the eastern portion of the State of Nebraska,USA.Within the Rolling Hills Landform,three watersheds were randomly selected as calibration watersheds while two were randomly selected as validation watersheds.Two watersheds were randomly selected as calibration watersheds while one was randomly selected as a validation watershed within each of the Dissected Plains and Plains Landforms.The seven calibration watersheds were used to provide the necessary calibrated parameter sets to execute each of the regional approaches,while the four validation watersheds were used to assess the impact of applying each of these approaches to an uncalibrated watershed.Percent Bias(PBIAS)and the Nash Sutcliffe Coefficient of Efficiency(NSE)were used to assess model performance.Test results of this study show that all three methods performed poorly,since the majority of watersheds among each method tested exhibited PBIAS values greater than ±25% and/or NSE values less than 0.50,which were considered to be unsatisfactory in terms of model performance.The average regionalization,nearest neighbor and donor methods resulted in only four(two calibration and two validation),zero and one satisfactory set of simulated watershed results,respectively.The findings from this study indicate that although each watershed was successfully calibrated with NSE values ranging from 0.51 to 0.84,none of the three regionalization methods provided suitable calibration data sets to define parameter values for performing satisfactory simulations on ungaged watersheds across the eastern Nebraska landscape.