In this article, we propose a technique for the precise cleaning of the gravity anomaly database based on the cross validation approach. The terrestrial gravity anomalies were compared versus a global geopotential model and take into account the effect of topography in this comparison. The efficiency of the cross-validation technique is illustrated in outlier detection as well as in choosing the proper gridding technique as a case study in construction of the Iranian new gravity database. In order to reduce the effect of topography and the discretisation error, a special interpolation scheme is used for gridding of the free-air gravity anomalies. The final grid file was created based on the Kriging method with 80″ × 90″ block resolution. The overall accuracy for the new Iranian gravity database is estimated in the order of 10 mGal.
Authors:Andrea Del Bon, Chiara Sbarbati, Elio Brunetti, Valentina Carucci, Alessandro Lacchini, Valentina Marinelli and Marco Petitta
Although the Acque Albule Basin has been studied since the middle of the 19th century, a comprehensive geologic conceptual model of the area has not yet been developed. The natural setting has been heavily modified by anthropic activities. Rapid evolution during the last 25 years has caused many interferences, which have led to a drastic increase of the hazards and linked risks, mainly related to water resource overexploitation and subsidence.
The implementation of an exhaustive framework has become mandatory for environmental and management purposes. Starting from a critical review of previous studies, hydrogeologic and hydrogeochemical surveys and related numerical modeling have been carried out in order to achieve a quantitative understanding of the active phenomena and processes.
Several hydrogeologic issues have been addressed concerning aquifer recharge areas and the different flowpaths of groundwater in respect to their division into a shallow and a deep circuit. Account has been taken of the groundwater chemistry as a function of water—rock interactions and mixing processes with uprising fluids. Different scenarios of groundwater flow in the Acque Albule aquifer have been built, using previously available piezometric measurements and the hydrodynamic parameters determined by in situ tests. These results led to the formulation of an updated hydrogeologic conceptual model to be further implemented, in which past, present and future anthropic instances and the potential of natural resources of the area have been included and taken into account. A sound conceptual model must rely on the design and development of a logical geo-database in which information is stored, updated and processed. This operational framework can result in a useful tool for land management, surveys planning and design, hazard and risk evaluation, identification of best practices and economic development of the area.
Authors:N. H. Singh, J. Mathai, V. N. Neelakandan, D. Shankar and V. P. Singh
A series of unusual geological incidents have occurred throughout the Kerala State (southwest Peninsular India) during the year 2001 mainly in two active phases i.e. February to March, and June to November 2001. In the beginning during February-March 2001, oscillations and rise in water levels, wavy formations and spouting up of water in the open wells, cracks in the buildings, perceptible ground fissures, shaking of trees/bushes and enhanced microearthquake activity have occurred. Collapse of shallow open wells, draining of water, lowering of water level, land subsidence, ground fissures etc., and further increased microearthquake activity were the dominant incidents in various parts of the State during June to November 2001. Interestingly, no such incidents had occurred in the past in this region. The frequency of all the above incidents, including microearthquakes activity, reduced drastically to background level beyond November 2001 except a few earthquakes during 2002 and 2003. The incidents are distributed in a vast area irrespective of geology and topography right from coastal stretch to hinterlands in the Western Ghats of India. This chain of incidents was preceded by two moderate size earthquakes of M ~ 5 on 12 December 2000 and 7 January 2001 which were not capable to trigger such widespread incidents in the region. The temporal patterns of these incidents clearly indicate the phenomenon of rapid ground vibrations at several occasions possibly due to movement of crustal block along certain active fault. This geological process perhaps lead to uplift and tilt of the ground giving rise to several underground water related anomalies and incidents of land deformations. The temporal patterns of individual incident also did not show any clear inter-relationships indicating that all these incidents were caused by a single internal geological process possibly due to converging trend of tectonic stress through the process of redistribution. It is inferred that these incidents constitute a well defined patterns of precursory sequence to a future large seismic activity in the southwest part of Peninsular India. The existence of the present chain of events can be explained by dilatancy diffusion model. Using the spatial distribution of these incidents including microearthquake activity and past significant earthquakes, an east-west trending potential area (10.7-10.9°N; 76.0-76.8°E) is delineated in the central Kerala region as the preparatory zone for the location of future earthquake.
( Milota et al. 1995 ).
Depth of oil–water contact data of oil field reservoirs and related oil density data were collected from the database of the Hungarian Mineral Resource Inventory. The data from 769 reservoirs of 142 oil fields were available
Authors:Nikolett Bodnár, József Kovács and Ákos Török
Miocene siltstone with variable sand content and bentonitic clay is the most abundant sediments encountered at the metro construction site at Rákóczi Square (Budapest). Core logs, drilling reports and records of laboratory analyses were studied to better understand the local geology and to prepare a database on engineering geologic properties of the materials. Using this database, geologic sections were prepared and geomathematical methods were used to obtain a better correlation of the strata in the area and a reconstruction of the geologic evolution of the area. The samples were divided into five groups based on physical properties. These five parameters allowed the use of multivariate statistical methods as cluster and discriminant analysis. As a result it was possible to identify several types of lithotypes, including two bentonitic clays with substantially different properties, one fat clay, one medium clay and one sandy, lean clay and siltstone group.
Authors:Éva Hartai, Tibor Sasvári, Anna Seres and László Kuti
The Bodrogköz is predominantly a flat area surrounded by the rivers Tisza, Bodrog and Latorica. The Hungarian-Slovakian border cuts it into two parts; consequently, the geologic data in the two countries are different in terms of scale and in approach. The authors harmonized the different data on the two sides and created a unified geologic database for the entire area. The Bodrogköz is part of the depression at the northeastern part of the Great Hungarian Plain. It is covered mostly by Quaternary formations but in the Slovakian part there are smaller outcrops of Permian formations and Miocene volcanics.
Compet-Terra is carrying out QA (Quality Assurance) services for the Hungarian Agriculture and Regional Development Agency. Quality control of the LPIS is one of the important QA duties. The LPIS data set is updated yearly according to the cycles of agricultural subsidies. Compet-Terra elaborated an Open Source Software based checking method that could be adopted by the client without the financial expense of software.
QuantumGIS (as the primary tool), gvSIG, and LibreOffice were used for the quality control of the LPIS. Four primary quality types were checked: (1) the land parcel attributes, (2) the areas of the polygons, (3) the completeness of the content and (4) the topological quality. For these investigations topological GIS functions and database management functions were used. The most important functions were topological difference calculation, polygon area calculation and geometry validity check. Complex procedures were also carried out with proprietary tools to compare the results and the run-time performances.
The result of the adoption of OSS GIS tools for LPIS checking was positive. All the planned procedures could be implemented using OSS GIS. OSS tools proved to be robust, reliable, userfriendly and performed well.