S06d/S06e Strong Ground Motion: Site Effects and Rotational Seismology

IASPEI (Seismology, Geophysics)



01-Jul-2015, 15:00 - 16:30


 
Abstract content:

Methodology for seismic microzonation of Budapest, Hungary

Seismicity of Budapest is moderate but somewhat higher than the average in Hungary. The largest well known historical earthquake (M5.6) that affected the city occurred in 1956 near the village of Dunaharaszti, 5-10 km distance from the southern boundary of the capital. Seismic activity is still observable in the area. The quake caused damages in Budapest that were surveyed in detail after the event. The intensity on the MSK scale reached 7 degrees in some places of south Budapest and some areas of more severe damages could be also observed inside the city.
Geological structure of Budapest is very complex. On the right bank of the Danube, older Triassic and Miocene formations outcrop to the surface while on the left bank Holocene and Pleistocene sediments cover the area.
Seismic microzonation of the city is in progress now. In the first step, applicability of topographic slope as a proxy for seismic site conditions has been studied. S wave velocity measurements have been collected and compared with the relations developed for active and passive tectonic regions. We have concluded that relation developed for active areas can be applied however numerous velocity values showed significant deviations.
Microseismic noise measurements were carried out on areas where occurrence of resonance is expected on the basis of geological maps. Besides, areas where larger damages were experienced during Dunaharaszti earthquake were also investigated. We have determined resonance frequencies and studied directivity of horizontal-to-vertical spectral ratios. We have performed MASW and ReMi measurements to determine the S wave velocities in the upper sedimentary layers and have studied the local applicability of noise cross correlation method.

 
Author(s):
E. Gyori1, Z. Gráczer1, G. Szanyi1, P. Tildy2, P. Mónus1, K. Gribovszki1, L. Tóth1, M. Kiszely1, T. Czifra1.
1MTA CSFK Geodetic and Geophysical Institute, Seismological Observatory, Budapest, Hungary.
2Geological and Geophysical Institute of Hungary, Department of Engineering Geophysics, Budapest, Hungary.

 

Keywords:
topographic slope     microseismic noise     resonance     directivity     active and passive seismic     noise cross correlation