IGU commission on the world political map

The International Geographical Union Reports

IGU commission on the world political map     

Carbonatite occurrences of the world: map and database, by A. R. Woolley and B. A. Kjarsgaard.

Labour of love For those of us who do not have the genes needed for sorting,cataloguing, and pigeon-holing, we need those who do. This open-filereport (5796) from the Geological Survey of Canada entitledCarbonatite occurrences of the world: map and database includesa CD brimming, perhaps overflowing, with information about carbonatites.Woolley started listing alkaline rocks and carbonatites alongwith their ages, spatial distribution, and associated rockstypes in his volume on the carbonatites of North and South Americathat appeared in 1987. Since then, other volumes have appearedwith Woolley acting as the main     

Variation in pyrite size, form, and microlithotype association in the springfield (no. 9) and herrin (no. 11) coals, Western Kentucky

Channel samples of the Springfield (No. 9) and Herrin (No. 11) (Pennsylvanian, Desmoinesian/Westphalian D) coals were acquired in three mines each in the Western Kentucky coal field. Pyrite was characterized petrographically in terms of its size, form, and microlithotype association. Within each coal seam significant variations in the amount of pyrite of certain forms occurred between the sites. Pyritic sulfur as determined chemically did not exhibit significant variation between the seams or between the sites. The variation in dendritic pyrite in vitrite plus clarite between seams and between sites was highly significant and the variation in framboidal pyrite in vitrite plus clarite between sites was also highly significant.     

Site effects modelling applied to the slope affected by the Suusamyr earthquake (Kyrgyzstan, 1992)

In 1992, a large magnitude earthquake (Ms = 7.3) hit the northern part of the Kyrgyz Tien Shan range where it triggered rockslides and many debris slides or flows. One of these mass movements occurred on the Chet–Korumdy ridge located in the Suusamyr Basin. It consists of a multi-rotational debris slump in its upper part that turned into a debris flow in its lower part. Involving arenitic material overlying silty clays, it has a volume of about 0.5 to 1.10⁶ m³, a maximum thickness of 40 m and a run-out of 200 m. The field observations and measurements carried out on this slope suggest that local amplification effects could have contributed to the initiation of the seismic failure. To test this hypothesis in the lack of instrumental evidence of local ground-motion recordings, we conducted a sensitivity study of site effects based on a numerical analysis in the visco-elastic domain with a two-dimensional finite difference code. Varying the topography and the geology of the investigated slope, topographic site effects are found to be less important than geological site effects which are controlled by the contrast of impedance between the surface materials and the bedrock. The geometry of the low-velocity surface layer has also an influence on site effects, which is often difficult to be distinguished from pure topographic effects. Considering all modelling results, we conclude that site amplifications alone cannot have triggered the Suusamyr landslide during the 1992 earthquake. The static slope stability analyses done in previous studies revealed that the Suusamyr failure neither can have a purely static origin. Even if the water table is very high within the arenite layer, only a minor failure develops in the lower part of the slope. Therefore, we believe that the triggering of the Suusamyr landslide is a consequence of pore pressure build up in areas characterized by significant ground-motion amplifications.     

Liquefaction during the June 27, 1998 Adana-Ceyhan (Turkey) Earthquake

On June 27, 1998, a moderate earthquake measuring 5.9 on the Richter scale struck the alluvial plains of Cukurova in the Adana-Ceyhan region of Turkey. The earthquake resulted in 145 deaths, about a thousand injuries and significant damage to more than ten thousand structures. The coincidence of the projected location of the release of energy along the earthquake fault with a very vulnerable geological surface formation (the thick alluvial deposits of Ceyhan River containing loose sand layers) resulted in liquefied sediments of substantial thickness and extensive areal distribution. Liquefaction associated ground deformations such as lateral spreading, flow failures, ground fissures and subsidence, sand boils, and slope failures were observed. This paper presents and analyses the geotechnical aspects of this earthquake with the main emphasis on the observed liquefaction and associated ground deformations, together with the earthquake characteristics. The observed liquefaction mechanisms provide valuable information on the seismic response of the alluvial soils covering most of the Cukurova plains, an area of industrial and agricultural importance with more than 2 million inhabitants. The observations from this earthquake also provide us with an opportunity to further improve our understanding of the observed phenomena and their effects that can be expected during other future earthquake events around the world.