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Abstract: Pleistocene to present evaporitic lacustrine sediments in Lake Magadi, East African Rift Valley, Kenya were studied and mapped using spectral remote sensing methods. This approach incorporated surface mineral mapping using space-borne hyperspectral Hyperion imagery together with laboratory analysis, including visible, near-infrared diffuse reflectance spectroscopy (VNIR) measurements and X-ray diffraction for selected rock and soil samples of the study area. The spectral signatures of Magadiite and Kenyaite, which have not been previously reported, were established and the spectral signatures of trona, chert series, volcanic tuff and the High Magadi bed were also analyzed. Image processing techniques, MNF (Minimum Noise Fraction) and MTMF (Mixture Tuned Matched Filtering) using a stratified approach (image analysis with and without the lake area), were used to enhance the mapping of evaporates. High Magadi beds, chert series and volcanic tuff were identified from the Hyperion image with an overall mapping accuracy of 84.3%. Even though, the spatial distribution of evaporites and sediments in Lake Magadi area change in response to climate variations, the mineralogy of this area has not been mapped recently. The results of this study shows the usefulness of the hypersspectral remote sensing to map the surface geology of this kind of environment and to locate promising sites for industrial open-pit trona mining in a qualitative and quantitative manner. [Copyright &y& Elsevier]

Abstract: Geologists have used remote sensing data since the advent of the technology for regional mapping, structural interpretation and to aid in prospecting for ores and hydrocarbons. This paper provides a review of multispectral and hyperspectral remote sensing data, products and applications in geology. During the early days of Landsat Multispectral scanner and Thematic Mapper, geologists developed band ratio techniques and selective principal component analysis to produce iron oxide and hydroxyl images that could be related to hydrothermal alteration. The advent of the Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) with six channels in the shortwave infrared and five channels in the thermal region allowed to produce qualitative surface mineral maps of clay minerals (kaolinite, illite), sulfate minerals (alunite), carbonate minerals (calcite, dolomite), iron oxides (hematite, goethite), and silica (quartz) which allowed to map alteration facies (propylitic, argillic etc.). The step toward quantitative and validated (subpixel) surface mineralogic mapping was made with the advent of high spectral resolution hyperspectral remote sensing. This led to a wealth of techniques to match image pixel spectra to library and field spectra and to unravel mixed pixel spectra to pure endmember spectra to derive subpixel surface compositional information. These products have found their way to the mining industry and are to a lesser extent taken up by the oil and gas sector. The main threat for geologic remote sensing lies in the lack of (satellite) data continuity. There is however a unique opportunity to develop standardized protocols leading to validated and reproducible products from satellite remote sensing for the geology community. By focusing on geologic mapping products such as mineral and lithologic maps, geochemistry, P-T paths, fluid pathways etc. the geologic remote sensing community can bridge the gap with the geosciences community. Increasingly workflows should be multidisciplinary and remote sensing data should be integrated with field observations and subsurface geophysical data to monitor and understand geologic processes. [Copyright &y& Elsevier]

Abstract: Surface deformations in L’Aquila (centre of Italy) caused by the April 6th, 2009 earthquake were studied from space geodesy and remote sensing points of view using Synthetic Aperture Radar Interferometry (InSAR) and Sub-pixel Correlation Technique (SCT). InSAR was used to measure ground surface deformation in the satellite line of sight (LOS) direction and the deformation was determined using two separate interferometric pairs of ENVISAT ASAR and ALOS PALSAR data sets. Furthermore, SCT was employed to investigate the horizontal displacements in the area. Two separate pairs of ENVISAT ASAR and ASTER optical image data sets were employed, and horizontal displacements in Range/Azimuth and in west–east/south–north directions were investigated, respectively. Maximum 28.1cm subsidence in LOS direction was observed on the descending interferogram of the ENVISAT ASAR data set, to the north-west of Onna village. The initial coseismic surface deformation started from the north of the main event epicentre. Most of the post-seismic relaxation occurred after April 7th, toward the south and south-east of the main shock epicentre, and results from SCT showed that the horizontal displacement was not significant on the surface (not more than a few centimetres). [Copyright &y& Elsevier]

Abstract: This paper is a response to the comments raised by Marco et al. referring to the work of on “Surface deformation caused by the April 6th 2009 earthquake in L’Aquila (Italy): A comparative analysis from ENVISAT ASAR, ALOS PALSAR and ASTER”. While some of the issues raised by them are relevant and appropriate, the authors believe that some of their comments arose from misunderstanding and needs some elaboration. In this paper, we address their comments and clarify the ambiguities. [Copyright &y& Elsevier]

A correction to the article "Using satellite remote sensing to assess evapotranspiration: Case study of the upper Ewaso Ng'iro North Basin, Kenya," by Jennifer Kinoti Mutiga and colleagues that was published in issue number 12 (S1) (2010) S100-S108 is presented.

A correction to the article "Estimation of spatial-temporal rainfall distribution using remote sensing techniques: A case study of Makanya catchment, Tanzania," by Jennifer Kinoti and colleagues that was published in issue number 12S1 (2009) S90-S99 is presented.