Derivation of sediments iso-frequency map for the Litija Basin (Central Slovenia) by microtremor analysis and implications for soil-structure resonance

Title:

Derivation of sediments iso-frequency map for the Litija Basin (Central Slovenia) by microtremor analysis and implications for soil-structure resonance

Creator:

Gosar, Andrej

Identifier:

https://cdk.lib.cas.cz/client/handle/uuid:814897c3-8f2c-4e97-a8b3-c0b381f557d5
uuid:814897c3-8f2c-4e97-a8b3-c0b381f557d5
issn:1214-9705

Subject:

Geologie. Meteorologie. Klimatologie, seizmicita, seismicity, microtremors, ambient vibrations, Horizontal-to-Vertical Spectral Ratio method, seismic site effects, soil-structure resonance, 7, and 551

Type:

article, články, model:article, and TEXT

Format:

print, bez média, and svazek

Description:

a2_The town of Litija was hit by four damaging earthquakes in the last 120 years which reached a maximum intensity of VII-VIII MSK. The town is located in a shallow sedimentary basin filled with relatively soft Quaternary sediments in which seismic site amplification is expected. On the other hand no borehole or geophysical data are available to support quantitative assessment of site effects. As a contribution to the first seismic microzonation of the area, we performed a free-field study based on the microtremor HVSR method in order to assess the resonance frequency of th e sediments. In ge neral clear spectral peaks were obtained for 57 measuring points which show distribution of frequencies in a broad range between 4.4 an d 22.7 Hz. The iso-frequency map was prepared by using natural neighbour interpolation algorithm. For soil-structure resonance assessment we considered large building stock from different Slovenian towns, because the building typology is similar in wider area. Low-rise masonry family houses with two or three floors prev ail. By microtremor measurements inside 45 such buildings their fundamental longitudinal and transver se frequencies were determined and statistically analysed in a complementary study. To assess the possible occurrence of soil-structure resonance in general, the average fundamental frequency +/- one standard devia tion interval is obtained for these two building heights, which give s the range 5.6-11.1 Hz. The free-field microtremor data shows that this frequency range occupies 37% of the urban area in the Litija basin. This study has shown that soil-structure resonance issue for low-rise buildings is frequently overlooked, but should be considere d seriously in shallow sedimentary basins, characterized by relatively high free-field frequencies, because many towns are located in such geological environment., a2_Second application of the derived iso-frequency map is to support soil classification, because recent investigations have shown that fundamental frequency of sediments can be used together with the average shear velocity in the upper 30 m to improve classi fications according to di fferent seismic codes., Andrej Gosar., and Obsahuje bibliografické odkazy

Language:

English

Rights:

http://creativecommons.org/licenses/by-nc-sa/4.0/
policy:public

Source:

Acta geodynamica et geomaterialia : | 2012 Volume:9 | Number:2 (166)

Harvested from:

CDK

Metadata only:

false