Effect of spatial variation characteristics on contouring of design storm depth

The ordinary kriging method, a geostatistical interpolation technique, was applied for developing contour maps of design storm depth in northern Taiwan using intensity–duration–frequency (IDF) data. Results of variogram modelling on design storm depths indicate that the design storms can be categorized into two distinct storm types: (i) storms of short duration and high spatial variation and (ii) storms of long duration and less spatial variation. For storms of the first category, the influence range of rainfall depth decreases when the recurrence interval increases, owing to the increasing degree of their spatial independence. However, for storms of the second category, the influence range of rainfall depth does not change significantly and has an average of approximately 72 km. For very extreme events, such as events of short duration and long recurrence interval, we do not recommend usage of the established design storm contours, because most of the interstation distances exceed the influence ranges. Our study concludes that the influence range of the design storm depth is dependent on the design duration and recurrence interval and is a key factor in developing design storm contours. Copyright © 2003 John Wiley & Sons, Ltd.     

Validation of Landslide Susceptibility Maps; Examples and Applications from a Case Study in Northern Spain

A procedure for validating landslide susceptibility maps wasapplied in a study area in northern Spain and the results obtained compared. Validationwas used to carry out sensitivity analysis for individual variables and combinationsof variables. The validity of different map-making methods was tested, as well as theutility of different types of Favourability Functions. The results obtained show thatvalidation is essential to determine the predictive value of susceptibility maps. Italso helps to better select the most suitable function and significant variables, thus improving the efficiency of the mapping process. Validation based on a temporal strategy makes it possible to derive hazard maps from susceptibility maps.     

On the observations of Mount St Helens volcanic emissions: Research note

Abstract

The envelopes of dust clouds from the May 18, 1980 eruption of Mount St Helens in Washington State, U.S.A. were plotted as they traversed the northern United States and southern Canada. Visibility observations at many meteorological stations indicated the presence of volcanic ash and smoke and verified trajectory calculations. In addition, sulphur dioxide released by the volcano was detected as it passed over Toronto, Ontario, while satellite photographs showed dust clouds in the upper atmosphere.     

Logistic regression model for sinkhole susceptibility due to damaged sewer pipes

The occurrence of anthropogenic sinkholes in urban areas can lead to severe socioeconomic losses. A damaged underground sewer pipe is regarded as one of the primary causes of such a phenomenon. This study adopted the best subsets regression method to produce a logistic regression model that evaluates the susceptibility for sinkholes induced by damaged sewer pipes. The model was developed by analyzing the sewer pipe network as well as cases of sinkholes in Seoul, South Korea. Among numerous sewer pipe characteristics tested as explanatory variables, the length, age, elevation, burial depth, size, slope, and materials of the sewer pipe were found to influence the occurrence of sinkhole. The proposed model reasonably estimated the sinkhole susceptibility in the area studied, with an area value under the receiver-operating characteristics curve of 0.753. The proposed methodology will serve as a useful tool that can help local governments to choose a cavity inspection regime, and to prevent sinkholes induced by damaged sewer pipes.     

Is Prediction of Future Landslides Possible with a GIS?

This contribution explores a strategy for landslide hazard zonation inwhich layers of spatial data are used to represent typical settings inwhich given dynamic types of landslides are likely to occur. Theconcepts of assessment and prediction are defined to focus on therepresentation of future hazardous events and in particular on themyths that often provide obstacles in the application of quantitativemethods. The prediction rate curves for different applications describethe support provided by the different data layers in experiments inwhich the typical setting of hazardous events is approximated bystatistically integrating the spatial information.     

40Ar/39Ar dating of the Jiali and Gaoligong shear zones: Implications for crustal deformation around the Eastern Himalayan Syntaxis

We conducted a comprehensive ⁴⁰Ar/³⁹Ar geochronological study of the Jiali and Gaoligong shear zones to obtain a better understanding of crustal deformation and tectonic evolution around the Eastern Himalayan Syntaxis (EHS). The new age data reveal that the main phase of deformation in the Jiali and Gaoligong shear zones occurred from 22 to 11 Ma and from 18 to 13 Ma, respectively. Structural data collected during this study indicate that the Jiali shear zone underwent a change in shear sense from sinistral to dextral during its movement history. Based on a comparison with the deformation histories of other major shear zones in the region, we argue that the initial sinistral motion recorded by the Jiali shear zone was coincident with that of the Ailao Shan–Red River shear zone, which marked the northern boundary of the southeastward extrusion of the Indochina block during the Early Miocene. From the Middle Miocene (～18 Ma), the Jiali shear zone changed to dextral displacement, becoming linked with the dextral Gaoligong shear zone that developed as a consequence of continued northward indentation of the Indian continent into Asia. Since this time, the Jiali and Gaoligong shear zones have been united, defining the southwestern boundary of the EHS during clockwise rotation of the eastward-extruding Tibetan block, as revealed by recent GPS data. The temporal change in regional deformation pattern from southeastward block extrusion to clockwise rotation of crustal fragments may have played an important role in the development of the eastern Himalayan drainage system around the EHS.     

Development and application of a GIS-based tool for earthquake-induced hazard prediction

An integrated GIS-based tool (GTIS) was constructed to estimate site effects related to the earthquake hazards in the Gyeongju area of Korea. To build the GTIS for the study area, intensive site investigations and geotechnical data collections were performed and a walk-over site survey was additionally carried out to acquire surface geo-knowledge data in accordance with the procedure developed to build the GTIS. For practical applications of the GTIS used to estimate the site effects associated with the amplification of ground motion, seismic microzoning maps of the characteristic site period and the mean shear wave velocity to a depth of 30 m were created and presented as a regional synthetic strategy addressing earthquake-induced hazards. Additionally, based on one-dimensional site response analyses, various seismic microzoning maps for short- and mid-period amplification potentials were created for the study area. Case studies of seismic microzonations in the Gyeongju area verified the usefulness of the GTIS for predicting seismic hazards in the region.     

Grain size trend and hydrodynamic condition of tirumalairajan River estuary,east coast of India

The estuary can be considered as environments characterized by high productivity and uncommensurable ecological value. However, marine ecosystems are also subjected to high human pressures that increase their vulnerability. The aim of this work is to analyze grain size trend of sediment due to the action of the main hydrodynamic condition. The spatial distribution patterns of sediments were monitored according to season. The grain-size trend of surficial sediments revealed a dominant sediment transport trend towards the eastern and south eastern part of study area. This study shows that there is an agreement among sediments path ways, hydrodynamic condition and the sediment spatial distribution in the estuarine environment. The agitation by waves is an important sorting mechanism in the study area. The findings are based on the grain size trend and also corroborated by short term observations of the estuarine sediment dynamics and transport during the monsoon, postmonsoon, summer and premonson seasons in Tirumalairajan River estuary.     

Estimating areal production of intertidal microphytobenthos based on spatio-temporal community dynamics and laboratory measurements

In situ Microphytobenthic community dynamics were combined with laboratory measurement of predominant species by fluorescence methods to estimate the areal primary production. Field investigation of community dynamics of microphytobenthos (MPB) was conducted from August 2006 to August 2007 in intertidal flats of the Nakdong River estuary, Korea. MPB Biomass varied between 0.47 and 16.58 μg cm^?3 in the surface 1 cm sediment, with two dominant diatom species, Amphora coffeaeformis and Navicula sp., occupying average 77.2 ± 14.9% of total number of MPB cells. The biomass was higher in the slightly muddy sand sites than that in the sand site, and showed different pattern of seasonal variation. The profile of vertical distribution of biomass was an exponential decrease trend with depth in sediments. The biomass proportions in the uppermost 3 mm were 57.6% and 37.8% with and without the presence of biofilm, respectively. The two dominant species were cultured in laboratory, and their photosynthetic parameters, rETR_max (relative maximum electron transport rate), α (light utilization coefficient) and E _k (light saturation parameter) were derived from rETR (relative ETR)-irradiance curves by Imaging- PAM (pulse amplitude modulated) fluorometry. The rETR-irradiance curves showed no significant difference of photosynthetic activities between the two species. The areal potential production ranged from 0.74 to 2.22 g C m^?2 d^?1.