Evaluation of Liquefaction Potential Index Along Western Coast of South Korea Using SPT and CPT

For South Korea, liquefaction potential along the western coast has not been widely assessed because South Korea is considered to be a low seismic hazard. However, recent earthquake events and historical records indicate that the seismic hazard of South Korea should not be ignored. Moreover, as artificial fills are extensively used along the western coast for development, liquefaction evaluation of the soils in this area is necessary. In this paper, we present: (1) the seismic characteristics of the study area; (2) procedures for evaluating liquefaction potential, focusing on the liquefaction potential index (LPI) approach; and (3) LPI distributions at several representative locations along the western coast of South Korea under various seismic scenarios. The liquefaction potential index represents the liquefaction potential over the upper 20 m of a boring or sounding. Using cone penetration test (CPT) and standard penetration test (SPT) data from two coastal sites, we compare and discuss CPT-based and SPT-based LPI values, particularly values computed in nonplastic, silt-rich soils. In these soils, it appears that the CPT yields lower liquefaction resistance, resulting in large LPI values. Finally, discussion and suggestions are provided for CPT- and SPT-based liquefaction assessment of low plasticity and high fines content soils.     

Estimation of non-CO2 GHGs emissions by analyzing burn severity in the Samcheok fire, South Korea

This study was performed to estimate the emission of non-CO 2 greenhouse gases(GHGs) from biomass burning at a large fire area.The extended methodology adopted the IPCC Guidelines(2003) equation for use on data from the Samcheok forest fire gathered using 30 m resolution Landsat TM satellite imagery,digital forest type maps,and growing stock information per hectare by forest type in 1999.Normalized burn ratio(NBR) technique was employed to analyze the area and severity of the Samcheok forest fire that occurred in 2000.The differences between NBR from pre-and post-fire datasets are examined to determine the extent and degree of change detected from burning.The results of burn severity analysis by dNBR of the Samcheok forest fire area revealed that a total of 16,200 ha of forest were burned.The proportion of the area characterized by a ’Low’ burn severity(dNBR below 152) was 35%,with ’Moderate’(dNBR 153-190) and ’High’(dNBR 191-255) areas were at 33% and 32%,respectively.The combustion efficiency for burn severity was calculated as 0.43 for crown fire where burn severity was ’High’,as 0.40 for ’Moderate’ severity,and 0.15 for ’Low’ severity surface fire.The emission factors for estimating non-CO 2 GHGs were separately applied to CO 130,CH 4 9,NO x 0.7 and N 2 O 0.11.Non-CO 2 GHGs emissions from biomass burning in the Samcheok forest fire area were estimated to be CO 44.100,CH 4 3.053,NO x 0.238 and N 2 O 0.038 Gg.     

Understanding of the Common Land Model performance for water and energy fluxes in a farmland during the growing season in Korea

The Common Land Model (CLM) is one of the most widely used land surface models (LSMs) due to the practicality of its simple parameterization scheme and its versatility in embracing a variety of field datasets. The improved assessment of land surface water and energy fluxes using CLM can be an alternative approach for understanding the complex land–atmosphere interactions in data‐limited regions. The understanding of water and energy cycles in a farmland is crucial because it is a dominant land feature in Korea and Asia. However, the applications of CLM to farmland in Korea are in paucity. The simulations of water and energy fluxes by CLM were conducted against those from the tower‐based measurements during the growing season of 2006 at the Haenam site (a farmland site) in Korea without optimization. According to the International Geosphere–Biosphere Programme (IGBP) land cover classification, a homogeneous cropland was selected initially for this study. Although the simulated soil moisture had a similar pattern to that of the observed, the former was relatively drier (at 0·1 m³ m^?3) than the latter. The simulated net radiation showed good agreement with the observed, with a root mean squared error (RMSE) of 41 W m^?2, whereas relatively large discrepancies between the simulation and observation were found in sensible (RMSE of 66 W m^?2) and latent (RMSE of 60 W m^?2) heat fluxes. On the basis of the sensitivity analysis, soil moisture was more receptive to land cover and soil texture parameterizations when compared to soil temperature and turbulent fluxes. Despite the uncertainty in the predictive capability of CLM employed without optimization, the initial performance of CLM suggests usefulness in a data‐limited heterogeneous farmland in Korea. Further studies are required to identify the controls on water and energy fluxes with an improved parameterization. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of the inter-annual variability of rainfall statistics on stochastically generated rainfall time series: part 2. Impact on watershed response variables

This study analyzes how the stochastically generated rainfall time series accounting for the inter-annual variability of rainfall statistics can improve the prediction of watershed response variables such as peak flow and runoff depth. The modified Bartlett–Lewis rectangular pulse (MBLRP) rainfall generation model was improved such that it can account for the inter-annual variability of the observed rainfall statistics. Then, the synthetic rainfall time series was generated using the MBLRP model, which was used as input rainfall data for SCS hydrologic models to produce runoff depth and peak flow in a virtual watershed. These values were compared to the ones derived from the synthetic rainfall time series that is generated from the traditional MBLRP rainfall modeling. The result of the comparison indicates that the rainfall time series reflecting the inter-annual variability of rainfall statistics reduces the biasness residing in the predicted peak flow values derived from the synthetic rainfall time series generated using the traditional MBLRP approach by 26–47 %. In addition, it was observed that the overall variability of the peak flow and run off depth distribution was better represented when the inter-annual variability of rainfall statistics are considered.     

Verification and validation of a seismic response analysis code for framed structures using the ASI‐Gauss technique

In this report, the capabilities of the adaptively shifted integration (ASI)‐Gauss code in the analysis of the seismic responses of framed structures are verified and validated by comparing the results with detailed numerical simulations performed by the parallel finite element analysis code, E‐Simulator, and with experimental results obtained by E‐Defense. The numerical results obtained by both codes showed good agreement with the experimental results obtained by E‐Defense. Furthermore, seismic waves with unnaturally large magnitudes are applied to a high‐rise building model to demonstrate the ability of the ASI‐Gauss code to analyze the collapse behaviors of building frames. Copyright © 2013 John Wiley & Sons, Ltd.     

Ensemble-based landslide susceptibility maps in Jinbu area, Korea

Ensemble techniques were developed, applied and validated for the analysis of landslide susceptibility in Jinbu area, Korea using the geographic information system (GIS). Landslide-occurrence areas were detected in the study by interpreting aerial photographs and field survey data. Landslide locations were randomly selected in a 70/30 ratio for training and validation of the models, respectively. Topography, geology, soil and forest databases were also constructed. Maps relevant to landslide occurrence were assembled in a spatial database. Using the constructed spatial database, 17 landslide-related factors were extracted. The relationships between the detected landslide locations and the factors were identified and quantified by frequency ratio, weight of evidence, logistic regression and artificial neural network models and their ensemble models. The relationships were used as factor ratings in the overlay analysis to create landslide susceptibility indexes and maps. Then, the four landslide susceptibility maps were used as new input factors and integrated using the frequency ratio, weight of evidence, logistic regression and artificial neural network models as ensemble methods to make better susceptibility maps. All of the susceptibility maps were validated by comparison with known landslide locations that were not used directly in the analysis. As the result, the ensemble-based landslide susceptibility map that used the new landslide-related input factor maps showed better accuracy (87.11% in frequency ratio, 83.14% in weight of evidence, 87.79% in logistic regression and 84.54% in artificial neural network) than the individual landslide susceptibility maps (84.94% in frequency ratio, 82.82% in weight of evidence, 87.72% in logistic regression and 81.44% in artificial neural network). All accuracy assessments showed overall satisfactory agreement of more than 80%. The ensemble model was found to be more effective in terms of prediction accuracy than the individual model.     

The twentieth century contiguous US temperature changes indicated by daily data and higher statistical moments

The daily surface air temperature data are used to assess the climate changes of the contiguous United States during the period of 1901 to 2000. The assessment is made through the first four statistical moments of the daily maximum, minimum, and mean temperature anomalies, the linear trends of the moments, and the changes of the anomalies?? probability density functions. The results on the first moment, i.e., the mean, are compared with the existing ones in terms of intra-annual means and their linear trends. Our first moment results agree with known ones and demonstrate a decrease from the 1930s to the 1960s and an increase from the 1970s to 2000. The temperature fluctuation is the smallest in the 1960s among the decades from 1931 to 2000. The trends of the higher (second-, third- and fourth-order) moments of the mean, maximum, and minimum surface air temperatures are calculated for the periods 1901?C2000, 1910?C1945, 1946?C1975, and 1976?C2000. The results show a decreasing trend of the second- and third-order moments of all the temperatures. The fourth-order moments of the mean and maximum surface air temperatures have increasing trends, but that of the minimum surface air temperature has a decreasing trend. The seasonal histograms of the mean, maximum, and minimum surface air temperatures are calculated for the three periods 1910?C1945, 1946?C1975, and 1976?C2000 for the stations which have the largest trend of maximum daily surface air temperature. An obvious change has been identified in the probability density functions. Among the changes of statistical parameters, the ones for the minimum temperature are larger than those for the maximum and mean temperatures.     

Possible linkage between East Asian summer drought and North Pacific Oscillation

The May North Pacific Oscillation Index and the summer (May and June?CJuly?CAugust??JJA) Effective Drought Index have a strong negative correlation in the East Asian region, particularly in northern China, Korea, and the southwestern regions of Japan (here termed ??Northeast Asia??); this signifies an intensification of the summer drought during positive North Pacific Index (NPI) phase in this region, and the presence of such a phenomenon has been observed in this study. The low-south/high-north anomalous pressure pattern forming in all layers of the troposphere in Northeast Asian region has been a cause of drought. This unusual pressure pattern gives rise to a cold northeasterly and intensifies downward flow and reduces relative humidity. In addition, this cold northeasterly hinders the northward movement of the western North Pacific high and reduces the frequency of tropical cyclones passing through this region, thereby further intensifying drought.     

Ecological significance of alkaline phosphatase activity and phosphatase-hydrolyzed phosphorus in the northern part of Gamak Bay, Korea

We investigated the ecological significance of alkaline phsophatase (APase) and alkaline phosphatase-hydrolyzable phosphorus (APHP) in the northern part of Gamak Bay, Korea. APase activity was detectable throughout the year, and dissolved inorganic phosphorus (DIP) concentration and APase activity are highly correlated and can be regarded as an indicator of DIP-limiting conditions. Also, a strong linear positive correlation between APase activity and Chl a concentration indicated that the major part of APase activity may have been induced by phytoplanktons. The APHP proportion in dissolved organic phosphorus (DOP) was above ca. 30% from winter to spring and below ca. 15% from summer to autumn due to freshwater discharge and uptake by phytoplankton. APHP may play an important role in species competition in coastal area such as northern part of Gamak Bay where DIP is limiting. Thus, APase induction by phytoplanktons may be ecologically significant, allowing dominance by these organisms under DIP-limiting conditions.