Geodetic Engineering
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Proceedings of the 11th WSEAS International Conference on Sustainability in Science Engineering Geodetic engineering – important tool for Romanian seismicity study CARMEN GRECEA Department of Land Measurements and Cadastre POLITEHNICA University of Timisoara 300006 Timisoara, P-ta Victoriei no. 2 ROMANIA [email protected] http://www.upt.ro Abstract: - Geodesy provides facilities to investigate the Earth’s crust movements and shares these data with other disciplines. With the rapid developments of geodetic techniques and the accuracy and reliability in geodetic measurements, the surveying methods have gained importance for monitoring crustal deformation on earthquake researches. The main purpose of the paper is to offer an overview of the situation existing in Romania, mainly in Banat county, regarding crustal deformation and propose solutions for future monitoring from geodetic points of view. Key- words: crustalmovements, monitoring, seismogenic, GPS, processing, seismic hazard, mapping 1 Introduction (M=7.2) were the largestin this century. Itis believed thatthe greatearthquake of 1802 may have reached Medium- to short term earthquake prediction is M=7.7. The upper limit of magnitudes for Vrancea becoming ever more essential for safeguarding man, earthquakes is in the region of M=8.0. Other source but until now there is no method for reliable zones (in the Fagaras Mountains and Banat) are earthquake prediction developed. Having one of the crustal, and generate lower magnitudes - seldom most seismically active area in Europe, Romania exceeding M=6.0. presents a relatively high potential of seismic risk Seismological information for Vrancea earthquakes is mainly due to the subcrustal earthquakes located in the plentiful, primarily due to their high frequency of Southeastern Carpathians. occurrence. Assuming that the data are complete for Seismic activity in Romania is due to Vrancea large magnitudes for the last 600 years, this time intermediate-depth subcrustal source(focal depth interval shows 3 earthquakes / century with Mw > 7.2 between 60 and 170km), and to severalshallow crustal and 6 events/century with Mw > 6.8. source(Banat, Fagaras, etc). Vrancea source dominates In Romania there are several significant areas of seismic hazard not only in Romania but also in seismicity with earthquakes at normal depths (less Republic of Moldova and affects large areas in than 60 km). The most active zones are in the western Bulgaria and Ukraine. partof Romania near the city of Timisoara (Banat and Romania is a moderate to high seismic area and its Danube Seismogenic Zones), in the central part near history reminds of frequent disasters caused by Sibiu (FC) and in the north western part at Baia Mare. earthquakes. Of all its seismic zones, the most important and well known is the Vrancea zone, in the Carpathians Arc Bend. This area is characterized by intermediate deep and crustal earthquakes, seismic high rate (4 to 5 destructive earthquakes per century) and intensive looses on large areas, surpassing Romanian borders. For the Vrancea seismogenic Region (VSR) the historical records of subcrustal earthquake occurrences are fairly more than a millennium. The earliest event in those catalogues is an earthquake occurred during the year 984. During this time period at least 37 strong events, thatis with Fig.1, Seismicity in Romania (www.infp.ro) maximum intensity VIII (MSK) or more are gathered into file. In factthatintensity is the level/threshold at The developmentof seismic monitoring in Romania is which the tremors are damage. The earthquakes of 10 a major contribution to research evolution in this November 1940 (M=7.4), and of 4 March 1977 domain, creating the premises for a better ISSN: 1790-2769 102 ISBN: 978-960-474-080-2 Proceedings of the 11th WSEAS International Conference on Sustainability in Science Engineering understanding and modeling of earthquake ground Fusion of satellite, GPSand field data in the evaluated motion, site effects and building response. area can provide a better monitoring of different geophysicalparameters and long term deformation in relation with earthquake activity. Multispectral and multitemporal satellite images covering the last 30 years have been analyzed for recognizing the continuity and regional relationships of active faults as well as for geological and seismic hazard mapping. Permanent GPS Romanian network data revealed a displacement of about 5-6 millimeters/year in horizontal direction relative motion, and also a few millimeters/year in vertical direction[8]. Fig.2, Tectonic overview map of the Carpathian region Deformation monitoring is conducted for the purpose of detecting and interpreting small changes in the geometric status of the earth. With the rapid developments of modern geodesy, and with the unprecedented accuracy achievable in geodetic measurements using advanced techniques, the geodetic methods have gained world-wide acceptance for monitoring crustaldynamics for earthquake studies. It Fig.3, The National Network of PermanentGNSS is important to measure both the long-term rate of Stations in Romania deformation and the shortterm deformation associated with the seismic activity along individual faults. The During recent years remote sensing and geospatial first type of measurement requires accurate information tools and technique, including numerical topographic maps to quantify the cumulative modeling, have advanced considerably. These tools displacement of surfaces. The second type of offer a greater understanding of the Earth as a complex measurements requires the capacity of estimating system of geophysical phenomena, including where displacements of the ground at millimeter level of and when hazards may occur, and what impact they precision over short time intervals. Contrary to the may have on the natural and built environment, and geologicalresearch, the studies of crustaldeformation society itself. are based on the analysis of repeated geodetic The information obtained from such systems is measurements, and their combination with results of beginning to be operational to decision makers for other geophysical investigations. Geodesy provides management in case of emergencies. facilities to investigate the Earth’s crust movements Satellite remote Sensing sensors gives a systematic and shares these data with other disciplines. framework for advancing scientific understanding of Using a growing network of instruments, methods and the Earth, as a complex system of geophysical information, scientists and engineers could be able to phenomena, that directly and through interacting suggest further improvements in order to help and processes, often lead to natural earthquake hazards. protect citizens from loss of life and property in future Space-based geodetic measurements of the solid Earth events. with GlobalPositioning System, combined with field Lately, due to the development of geodetic and seismological measurements provide the principal surveying techniques and methods, also the accuracy data for modeling lithospheric processes as well and reliability in geodetic measurements, this science as for accurately estimating the distribution of of terrestrial and spatial measurements has gained potentially damaging strong ground motions, importance for monitoring crustal deformation on critical for earthquake engineering applications. earthquake researches. ISSN: 1790-2769 103 ISBN: 978-960-474-080-2 Proceedings of the 11th WSEAS International Conference on Sustainability in Science Engineering 2. Contribution of Geodesy in aboutthe movements of the crust deformation, out of interdisciplinary studies for Earth’s which could have been computed the quantity of the potentialaccumulated energy between severalseries of crust movements measurements made into the determined limits. Thus, according to the theory of tectonic plates, which The study of the recent crustal movements could be confirms the fact that nothing is unflexible in the integrated in the ensemble of the scientific research whole nature, in time or space, ithas been enforced as with a fundamentalcharacter involving allgeosciences very necessary the introduction of the fourth that study the Earth dynamism, understanding the dimension (time) in processing of repeated geodetic description of all complex phenomena which are measurements. permanently taking place in the Earth’s crust and Identifying movements (including deformations) of much deeper. Combining the results obtained by the the upper side of the Earth’s crust, which are geology, geophysics, oceanographic sciences with the happening before, during or after the earthquake, by component of geodetic determinations, a multitude of geodetic methods, give them a fundamental research issues regarding the evolution of the changes from the character, and also a practical one, competing to the internalstructure and from the upper side of the Earth determination of stability degree of the ground in the crustcan be elucidated. populated areas or in the areas where important The participation of Geodesy in the studying programs industrial or edilitar objectives are about to be placed. of the crustal movements was determined and Classification of geodetic determinations of the developed with the agreement of the global tectonic Earth’s movements can be done: concept. The Geodesy provide accurate information • REGARDING THE REFERENCE SYSTEM Absolute determinations Relative determinations of vertical, horizontal and three- dimensionalmovements • REGARDING THE AMPLITUDE