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: crustal movements, monitoring, seismogenic, GPS, processing, seismic hazard, mapping 1 Introduction (M=7.2) were the largest in this century. It is believed that the great earthquake 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 several shallow 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. part of 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, that is with Fig.1, Seismicity in Romania (www.infp.ro) maximum intensity VIII (MSK) or more are gathered into file. In fact that intensity is the level/threshold at The development of 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, GPS and field data in the evaluated motion, site effects and building response. area can provide a better monitoring of different geophysical parameters 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 crustal dynamics for earthquake studies. It Fig.3, The National Network of Permanent GNSS is important to measure both the long term rate of Stations in Romania deformation and the short term 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 geological research, the studies of crustal deformation 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 Global Positioning 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 about the movements of the crust deformation, out of interdisciplinary studies for Earth’s which could have been computed the quantity of the potential accumulated energy between several series 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, it has been enforced as with a fundamental character involving all geosciences 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 internal structure and from the upper side of the Earth determination of stability degree of the ground in the crust can 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 dimensional movements • REGARDING THE AMPLITUDE OF RECENT MOVEMENTS DETERMINATIONS OF THE EARTH’S CRUST global determinations regional determinations local determinations • REGARDING THE GEODETIC DETERMINATION PRECISION • REGARDING THE RESULTS OBTAINED BY PROCESSING • REGARDING THE FINAL RESULT OBTAINED BY REPEATED GEODETIC MEASUREMENTS vertical movements map horizontal gradients of vertical movements
• REGARDING THE PROCESSING METHODS OF REPEATED GEODETIC MEASUREMENTS
determination of processing models in a movements and of status concept mobile entirely deformations processing models in a quasi status, quasi cinematic concept
ISSN: 1790-2769 104 ISBN: 978-960-474-080-2 Proceedings of the 11th WSEAS International Conference on Sustainability in Science Engineering
3. Seismological characteristics of the Banat Region The earthquake potential of the known local The western and south western part of Romania, seismic sources has been confirmed either by the often called the Banat Seismic Region (BSR), lies on maximum intensities/magnitudes observed in the the complex tectonic contact area between i) the historical period (1443 1970): IMAX=8 degree on Carpathian orogen (South Carpathians and Apuseni European Macroseismic Scale (EMS) /Ms=5.7, and Mountains) and ii) the subsidence structures of the the frequency of occurrence of the earthquakes (over south eastern border of Pannonian Depression seven thousands events are catalogued between 1443 (grabens, intra mountains depressions)[7]. and 2007 in the region; since 1880 the events with I>6 Banat Seismic Region is the most important seismic EMS occurred with an annual average frequency of 0.4). The epicentre are scattered all over in the Banat region of Romania when we refer to the seismic hazard determined by crustal earthquakes sources Seismogenic Zone (Western Plain of Romania), but (focal depth smaller than 60 km). The seismicity they cluster into small source zones that form several studies accomplished for defining the seismic hazard groups of active areas: Arad Sinnicolau Mare, Vinga sources from BSR define two main seismogenic Varias, Masloc Buzias, Jimbolia Sinmihai, Sag Parta, zones: Banat Seismogenic Zone and Danube Mosnita Recas, Banloc Voiteg and small areas along Seismogenic Zone the border of Romania with Serbia and Hungary. (Radulian et al. 2000) that correspond to the main The maximum magnitude/intensity observed in the regional morphological units developed in the region, region is Ms=5.7/8EMS (Banloc Voiteg, 1991). the Western Plain of Romania and South Carpathians The focal depth of the local earthquakes do not exceed mountain ranges, respectively. 25 km. The last stong earthquakes occured in the The geology and tectonics of this zone is very Banloc Voiteg area. This seismic source prolongs to complex: two major grabens elongated in NW SE the NNE up to South South East of Timisoara and continues uncertain to the North of Buzias (the direction, prevail in the zone: Sinnicolau Mare, Caransebes. Between these structures an uplifted Banloc Recas Fault). Between 1915 and 1991 it tectonic block extends from Buzias to Hungary generated three strong earthquakes: 19.09.1915, Io=VII VIIIOMSK/Mw =5.4; (Battonya Buzias horst). In the South, the Caras 12.07.1991, Io=VIIIOMSK/Mw =5.6 and graben is developed[7]. 02.12.1991, Io=VIIIOMSK/Mw=5.5. The historical earthquake epicenters distribution The subsequent seismic activity on a complex system reveals a very good spatial with the principal faults of faults, triggered by the 1991 strong earthquakes, from the region. The current seismicity emphasizes lasted many years, the area being actually one of three clusters around Timisoara. The first one occurred the most active areas from the region. in October 199 about 15 km NNW from Timisoara and the fault plane solution of the main event show a The seismic activity level recorded during the last normal faulting on a NE oriented plane. The other years recommends this seismic source area for a cluster is located about 30 km NE from Timisoara. multidisciplinary study and monitoring to know and better understand the seismogenic processes in the region.
Fig.5, Banat seismogenic zone Fig.4, Sketch of maximum principal stress tensor
ISSN: 1790-2769 105 ISBN: 978-960-474-080-2 Proceedings of the 11th WSEAS International Conference on Sustainability in Science Engineering
Taking into consideration the history of the field In remote sensing field, synergy use of data provides movements in Banat area, causes, intensity, means to combine satellite multispectral and propagation, it would be interesting to establish a multitemporal data. GPS is a very important tool for permanent solution for their evaluation using accurate crustal displacements assessment and surface geodetic technologies. It is planned to obtain 3D kinematics occurring in response to active crust realistic models of seismic faults from Banat and also lithosphere dynamics of Banloc area. In figure 6 and 7 to estimate their seismogenic potential and improving is presented a sketch of the seismotectonic features the seismotectonic models. The faults should be that support the GPS network (consisting 4 permanent investigated also by complementary seismic stations: Baia Mare, Deva, Bucure ti, Oros – Ungaria measurements. It is anticipated the transfer and the and 4 points of the national network: Mo niŃa, Gomila applicability of the results for initiation of other Mare, Grăniceri, Parto ) draft proposed for projects about the natural precursory phenomena of monitoring the faults system developed in the Banloc the earthquakes. Voiteg seismogenic area. Such a project could be developed for a multidisciplinary and interdisciplinary research of Sketch of the seismotectonic area that support the GPS network earthquakes from the western part of Romania, several Baia Mare Reference Station groups of active areas being implied: Arad Sinnicolau -3 Reference Station of EUREF Mare, Vinga Varias, Masloc Buzias, Jimbolia Reference network: Oros-Hungary, Sinmihai, Sag Parta, Mosnita Recas, Banloc Voiteg Oros Reference Station- Baia Mare, Deva; Hungary and 1 Reference Station of National Network of Permanent GPS Stations and small areas along the border of Romania with Timisoara Deva Reference Station Serbia and Hungary. Reference Station Gomila Mare - 4 points of National Geodesic Mosnita Network: Gomila Mare, Mosnita, Graniceri Graniceri, Partos Partos Distance maxim: 48 km 4. Global Positioning Systems – tool for Distance minimum : 24 km crustal movements evaluation Bucharest Reference Station The key to understand the Earth’s dynamics and system complexity is to integrate satellite observations at local, regional and global scales, over a broad portion of the electromagnetic spectrum with Fig,6, GPS network increasingly refined spectral resolution, spatial resolution and over times scales that encompass phenomenological lifecycles with requisite sampling frequency. Recent advances in computational science and numerical simulations are allowing the study of correlated systems, recognition of subtle patterns in large data volumes, and are speeding up the time necessary to study long term processes using observational data for constraints and validation. Integrating remotely sensed data into predictive models requires measurements at resolutions substantially superior to those made in the past when the observational systems and the discipline of natural hazards research were less mature than they are today. Fig.7, GPS monitoring network of the Banloc Furthermore, assimilation of data and model outputs seismogenic area into decision support systems must meet operational requirements for accuracy, spatial coverage and The proposed area for monitoring the faults system in timeliness in order to have positive impact on disaster Banloc is approx. 500 km2 risk management. Global Positioning System measurements can be used The idea of the project consists of combining the as reference to satellite remote sensing results, being satellite information from EUREF permanent stations necessary to interpolate deformations between the with data collected periodically from proposed interest GPS points. By combining these data sets can be also points shown before. improved the temporal resolution of the deformation.
ISSN: 1790-2769 106 ISBN: 978-960-474-080-2 Proceedings of the 11th WSEAS International Conference on Sustainability in Science Engineering
It is also proposed the installation of a permanent station inside the yard of the seismologic observatory in Timisoara which, together with the other 4 points(Mosnita, Gomila Mare, Graniceri, Partos – all of the first order in the national geodetic network), will generate a control network for measurements in the Banloc area[4]. Starting from this control network it will be developed a secondary network of detail points on the direction of the estimated faults. Integration of these data with crustal seismicity, surface geology, and topography through a Fig.8, Map of National Seismic Network containing: Geographic Information System (GIS) approach analog telemetric stations, digital broadband stations places critical constraints on the geodynamic and strong motion accelerographs settings for identifying the distribution, geometry, and type of active crustal faults, for elucidating the spatial relationship between the crustal References structures and mantle seismicity. With GPS geodesy can be recognized times and [1] Neuner J, Sisteme de pozitionare globala, Ed. locate areas of increased geophysical activity by MatrixRom, Bucuresti, 2000 mapping crustal deformation, seismicity, and [2] Oros E, L.NiŃoiu, Activitatea seismică other factors. înregistrată în regiunea Banat în perioada 01.01.2000 31.12.2000, Raport INFP Iulie 2001, Bucure ti 4. Conclusions [3] Euler H.J., C.R.Keenan, B.E.Zebhauser, Natural disasters involve the intersection of G.Wubbena, Study of a Simplified Approach in society, the built environment and natural Utilizing Information from Permanent Reference processes. The hazard is inevitable because we Station Array, ION GPS Salt Lake City USA, 2001 don’t know when an earthquake will strike, or how severe it will be. [4] Grecea C. et.al., Studies and geodetic The permanent development and application of solutions for future evaluations and monitoring crustal broad spectrum of satellite remote sensing movements in banat county, Journal of Geodesy and cadastre, nr.8/2008, pp.47 55 systems and attendant data management 5 Oros E., Seismicity, faults and faulting infrastructure will contribute needed baseline and [ ] time series data, as part of an integrated global mechanisms in South Western region of Romania, Postdam 2004 observation strategy that includes airborne and in situ measurements of the solid Earth. Seismic [6] Grecea C. et.al.,, UPTimisoara, Complemente hazard modeling capabilities, will result in more de Masuratori Terestre, Ed.Politehnica, accurate forecasting and visualizations for Timisoara, 2006 improving the decision support tools and systems [7] Oros E., Macroseismic and instrumental used by the international disaster management seismicity of the Banat region and its significance on community. the seismic hazard and risk, Symposium “Thirty Years It is anticipated the transfer and the applicability from the Romania Earthquake of March 4, 1977” of the results for initiation of other projects about Bucuresti, 2007. the natural precursory phenomena of the [8] Zoran M, Mateciuc D, Data fusion technique earthquakes. for seismic risk assessment, Proceedings of the The experiment can be developed for an International Symposium on Seismic Risk Reduction, Bucharest, Romanian Academy, april.2007, Ed. interdisciplinary research of earthquakes from the Orizonturi Universitare, Timisoara 2007, pp.291 299 western part of Romania. [9] www.nasa.com
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