Geo-risk management for developing countries—vulnerability to mass wasting in the Jemma River Basin,Ethiopia

A progress report of the M141 IPL project is presented. Conceptual and applied analyses bearing on engineering geological, hydrogeological mapping, and zoning of vulnerability to mass wasting were conducted for nearly a 16,000-km² area of the Jemma River basin, central Ethiopian highlands. Work was aimed at the specific modification of current methodology and its practical field testing, user-oriented information dissemination, and training of Ethiopian staff in geo-hazard assessment. Also, environmental protection studies and water resources management to improve food and sanitary security were provided. An alternative, conceptual energy-process and land unit-oriented and satellite images implementing method was developed to substitute for the inadequacy of information by regular field check and regular inventory of risky phenomena. It is necessary to implement a novel, complex systems paradigm to tackle vulnerability and risks in couplings of nature and human systems. This is discussed together with emphasis on user-oriented communication and building of geo-risk warning and management systems based on bottom-up, contextual approach.     

Hunting for Geochemical Associations of Elements: Factor Analysis and Self-Organising Maps

Two approaches, factor analysis (FA) and self-organising maps (SOM), have been used for the determination of geochemical associations in the two case studies evaluated here. In both case studies, different associations of elements, derived from different anthropogenic sources (smelters, ironworks, and chemical industry), are presented, together with natural associations of elements, all representing different geological environments. FA and SOM give similar results, despite some differences. Most similarities were achieved with the group of elements affected by strong pollution caused by smelting activities. The biggest difference between the two is that SOM can combine different groups into one, especially in the case of associations of elements connected with mild pollution (ironworking, chemical industry). The biggest advantage of SOM as opposed to FA is that SOM allow us to process variables, which are not normally distributed, or even of attributive nature. The use of such variables in SOM classification to prove the origins of associations of elements is also demonstrated here.     

Spheroidal Integral Equations for Geodetic Inversion of Geopotential Gradients

The static Earth’s gravitational field has traditionally been described in geodesy and geophysics by the gravitational potential (geopotential for short), a scalar function of 3-D position. Although not directly observable, geopotential functionals such as its first- and second-order gradients are routinely measured by ground, airborne and/or satellite sensors. In geodesy, these observables are often used for recovery of the static geopotential at some simple reference surface approximating the actual Earth’s surface. A generalized mathematical model is represented by a surface integral equation which originates in solving Dirichlet’s boundary-value problem of the potential theory defined for the harmonic geopotential, spheroidal boundary and globally distributed gradient data. The mathematical model can be used for combining various geopotential gradients without necessity of their re-sampling or prior continuation in space. The model extends the apparatus of integral equations which results from solving boundary-value problems of the potential theory to all geopotential gradients observed by current ground, airborne and satellite sensors. Differences between spherical and spheroidal formulations of integral kernel functions of Green’s kind are investigated. Estimated differences reach relative values at the level of 3% which demonstrates the significance of spheroidal approximation for flattened bodies such as the Earth. The observation model can be used for combined inversion of currently available geopotential gradients while exploring their spectral and stochastic characteristics. The model would be even more relevant to gravitational field modelling of other bodies in space with more pronounced spheroidal geometry than that of the Earth.