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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-24 11:34 |
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Conference: Bucharest University Faculty of Physics 2021 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Investigations on the behavior of the sedimentary structure during earthquakes: the correlation between f0 and fpred
Authors:
Alina COMAN (1,2), Elena Florinela MANEA (2), Carmen Ortanza CIOFLAN (2), Mircea RADULIAN (2)
*
Affiliation:
1. University of Bucharest, Faculty of Physics, 077125, Magurele, Romania
2. National Institute for Earth Physics, PO BOX MG2, 077125, Magurele, Romania
E-mail
coman@infp.ro
Keywords:
predominant frequency of resonance, seismic site effects, Vrancea crustal seismic area, H/V spectral ratio
Abstract:
Seismic site effects evaluation has a substantial impact on the assessment of seismic risk and hazard and it is a crucial step for the mitigation of potentially high seismic risk in densely populated urban regions. In this study, the predominant frequency of resonance (fpred) of S-waves was identified, interpreted and mapped along the regions covered by the National Seismic Networks of Romania, Bulgaria and the Republic of Moldova, for the crustal event produced on November 22, 2014, with the magnitude of 5.7 ML, generated at a depth of 40 km in the Vrancea seismogenic area. The spectral ratio (H/V) technique was applied on the three – component single station measurements to investigate the local variability on each region. The predominant observed peaks coincide with the fundamental resonance frequency, f0, (calculated from the H/V technique applied to ambient vibration recordings) for some stations located on superficial sedimentary layers and reach values higher than f0 in the case of stations located on deep sedimentary basins. In case of the stations located along the Carpathian arc and in the intra - Carpathian area, the fpred are identified at almost all the stations as f0 from ambient vibration. In case of the stations located in the extra - Carpathian area, in the northern side of Danube river, fpred is matching the second peak or has a higher frequency indicating a complex seismic response of the Moesian Platform geological structure. A significant attenuation can be observed for the sites located outside of this area (i.e. Northern Bulgaria and Dobrogea), where fpred matches the fundamental one, the seismic energy generated by the crustal event is not able to excite superior vibration modes in the local structures. These new results increase our understanding of ground motion propagation by emphasizing the ground motion peculiarities in this area for Vrancea crustal events.
Acknowledgement:
The seismic networks cited are the Romanian Seismic Network (RSN, https://doi.org/10.7914/SN/RO), National Seismological Network of Bulgaria (BAS, https://doi.org/10.7914/SN/BS) and Moldova Digital Seismic Network (https://doi.org/10.7914/SN/MD).
The software suite Geopsy (www.geopsy.org) and ArcGis (www.esri.com/software/arcgis) has been used for this study.
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