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50 330 345 Milne J 1886: Earthquakes and other earth movements. London, Kegan Paul, Trench and Co. Milne J

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Építés - Építészettudomány
Authors: Lajos Völgyesi, László Tóth, Erzsébet Győri, and Péter Mónus

A Budapest belvárosában található épületek döntő többsége a XIX–XX. században épült az akkori építészeti (főként klasszicista, illetve eklektikus) stílusoknak megfelelően, az adott technikai, építőmérnöki tudásnak és gyakorlatnak a lehetőségei és korlátai szerint. Mivel az emberek és a tervezők emlékeiben nem szerepeltek korábbi földrengések átélt tapasztalatai, nem gondoltak a szerkezetek tervezésekor a földrengésbiztonságra. Mai mérnökszeizmológiai ismereteink birtokában aggasztónak tűnik az épületek nagy részének helyzete egy esetleges, de egyáltalán nem kizárható budapesti vagy nagyobb Budapest közeli földrengés esetén. A tanulmányban áttekintjük az idősebb belvárosi téglaépületeket általánosan jellemző épületszerkezeti problémákat, foglalkozunk a belváros területének geológiai, talajmechanikai felépítésével, és a földrengéshullámok romboló hatását kedvezőtlenül befolyásoló talajviszonyokat is vizsgáljuk. Ehhez áttekintjük a Dunaharaszti közelében 1956-ban kipattant földrengés hatását Budapest területén, megvizsgáljuk, hogy a károk területi eloszlása milyen összefüggésben van az altalaj tulajdonságokkal. Az utóbbi időkben kipattant egyes földrengések (pl. L’Aquila, Emilia Romagna, Christchurch) során a keletkezett károk elemzése jó lehetőséget kínál megbecsülni a lehetséges károkozás nagyságrendjét egy itteni megfelelő méretű földrengés kipattanásakor, a hasonló szerkezetű budapesti épületek esetében.

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Abstract  

Immediately, after the July 9, 1997 earthquake (Ms = 6.8) in the state of Sucre, Venezuela, we began measuring radon in water to investigate the possible correlations with the seismic activity and to study the meteorological affects. Sampling periods were for 3–5 days with 4–8 weeks in between each. During the first two sampling periods, the seismic activity was high with several minor events (Mb4.0) and anomalous radon concentrations were measured and considered as possible precursors for the events. We have also shown that the radon activity was stable except for daily meteorological effects during periods of low seismic activity. The radon activity during the first year after the major event on July 9, 1997, at the beginning of the rainy season increased from about 50 pCi/l to about 350 pCi/l for all sampling points. Then abruptly dropped to 100 pci/l at the beginning of the next rainy season for points #1 and #2 in the Casanay river and stayed relativelystable during the second year. At the start of the third year, the values began to increase again, similarly to the first year. We concluded that this was caused by the heavy rainfall at the beginning of the rainy season. While at the sampling points at Hotel Cristal, thermal spring pool, it decreased slowly during the second year but increased again at the onset of the third year. Finally, we have concluded as other investigators, that monitoring radon activity alone is insufficient to predict minor earthquakes (Mb4.0), but in some cases it can be considered as a precursor.

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For a given earth model and hypocenter location, short-period local waveforms are inverted for the six unknown moment tensor rate functions (MTRFs) by a linear procedure. Subsequently, the MTRFs are decomposed into the source time function (STF) and the time independent moment tensor, fully describing the focal mechanism of the event. In case of short epicentral distances, routinely determined hypocenters are usually not accurate enough to be used in focal mechanism inversion. However, introducing hypocenter co-ordinates as unknown parameters leads to a nonlinear inversion problem. In order to solve this nonlinear problem, a probabilistic approach is applied in this study. The a priori probability density function (PDF) for the hypocenter location is given by a routinely used location algorithm. Assuming that all uncertainties can be described by Gaussian PDFs, measurement errors and theoretical errors are estimated. Then the results of the Bayesian approach are the posterior PDFs for both the hypocenter co-ordinates and the MTRFs. Decomposing the MTRFs, the PDFs for the STF and the moment tensor are also deduced. The estimated uncertainties in the moment tensor components are plotted on the focal sphere in such a way, that the significance of the double-couple, the CLVD, and the volumetric parts of the source can be assessed. The method is illustrated through the waveform inversion of a local event that occurred in the central part of the Pannonian Basin. The moment tensor solution for the selected event has negligible volumetric part, implying the tectonic nature of the event. The retrieved mechanism is in agreement with the available clear readings of first-arrival P-wave polarities. The principal axes of the resulting source mechanism also agrees well with the main stress pattern published for the epicentral region.

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building structures with identical stories subjected to earthquakes. International Journal of Solids and Structures 41 (5-6) (2004) 1411-1433. Approximate analysis of building structures with identical stories subjected to

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30 33 Tóth L, Mónus P, Zsíros T, Kiszely M, Czifra T 2005. Hungarian Earthquake Bulletin, 2004. GeoRisk, MTA GGKI, Budapest

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earthquake catalogue. Budapest, GGKI Seismicity and seismic risk of the Hungarian Basin: The Hungarian earthquake catalogue Tsuboi C 1956

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Sandi H 1985: In: Proc. 4th International Conf. on Structural Safety and Reliability (ICOSSAR ′85). Kobe Sandi H 1986: In: Proc. 8th European Conf. on Earthquake Engineering, Lisbon

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Ismail A 1960: Near and local earthquakes of Helwan (1903-1950). Helwan Observatory, Bull. No. 49. Near and local earthquakes of Helwan (1903-1950) Helwan Observatory, Bull

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Stamatovska S 1996: Empirical Non-Homogeneous Attenuation Acceleration Laws for Intermediate Earthquakes from Vrancea Subdustion Zone (doctoral thesis in Macedonian). Institute of Earthquake Engineering and Engineering Seismology, University “Ss. Cyril and

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