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Title:A microtremor HVSR study of the seismic site effects in the area of the town of Brežice (SE Slovenia)
Authors:ID Gosar, Andrej (Author)
ID Fakulteta za gradbeništvo, prometno inženirstvo in arhitekturo Univerze v Mariboru (Copyright holder)
Files:.pdf Acta_geotechnica_Slovenica_2009_Gosar_A_microtremor_HVSR_study_of_the_seismic_site_effects_in_the_area_of_the_town_of_Brezice_(SE_Sloven.pdf (403,95 KB)
MD5: 3DCAF4D68249A1A5949DA21A5F004E7E
PID: 20.500.12556/dkum/f0795bb3-2624-447a-bb82-92710648c65e
 
URL http://fgserver3.fg.um.si/journal-ags/2009-2/article-3.asp
 
Language:English
Work type:Scientific work
Typology:1.01 - Original Scientific Article
Organization:FGPA - Faculty of Civil Engineering, Transportation Engineering and Architecture
Abstract:The wider region of Brežice is one of the most seismically active areas of Slovenia. The most damaging earthquake occurred in 1917, when Brežice was hit by an ML=5.7 earthquake that had an VIII MSK maximum intensity. Seismic site effects due to Quaternary sediments can be expected in the whole area of the town. Since there is a lack of boreholes and geophysical data to assess the site effects, the microtremor (ambient vibrations) horizontal-to-vertical spectral ratio (HVSR) method was applied at 113 free-field measuring points. In general, clear spectral peaks were obtained, but there were also examples of flat spectral ratios indicating a low impedance contrast between the sediments and the bedrock. A map of the sediment resonance frequency was drawn, which shows a frequency range of 1–15 Hz. In the southern part of the town higher frequencies correspond to the thin sediments (the Brežice terrace and the middle Sava terrace) and the high HVSR peak amplitudes indicate a great impedance contrast with the Sarmatian and Badenian bedrock. The northern part is characterized by very low frequencies, indicating thick sediments (Plio-Quaternary gravel) and a small impedance contrast with Pontian marl. The transition between the high and low frequencies is relatively steep. In addition, measurements were performed in 12 characteristic houses to assess the longitudinal and transverse building frequencies. The established building frequency range of 5–10 Hz indicates some areas in the southern part of the town where there is a potential danger of soil-structure resonance. Two buildings show direct evidence of a potential soil-structure resonance. According to this study, more pronounced seismic site effects are expected in the southern part of Brežice.
Keywords:ambient vibrations, microtremors, horizontal-to-vertical spectral ratio (HVSR), seismic site effects, soil-structure resonance
Publication status:Published
Publication version:Version of Record
Year of publishing:2009
Number of pages:str. 31-45
Numbering:Letn. 6, št. 2
PID:20.500.12556/DKUM-70691 New window
ISSN:1854-017
UDC:55
ISSN on article:1854-0171
COBISS.SI-ID:803934 New window
NUK URN:URN:SI:UM:DK:2ZHYZK1B
Copyright:Fakulteta za gradbeništvo, prometno inženirstvo in arhitekturo Univerze v Mariboru
Publication date in DKUM:06.06.2018
Views:1396
Downloads:245
Metadata:XML DC-XML DC-RDF
Categories:Misc.
:
GOSAR, Andrej, 2009, A microtremor HVSR study of the seismic site effects in the area of the town of Brežice (SE Slovenia). Acta geotechnica Slovenica [online]. 2009. Vol. 6, no. 2, p. 31–45. [Accessed 7 April 2025]. Retrieved from: https://dk.um.si/IzpisGradiva.php?lang=eng&id=70691
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Record is a part of a journal

Title:Acta geotechnica Slovenica
Shortened title:Acta geotech. Slov.
Publisher:Fakulteta za gradbeništvo, prometno inženirstvo in arhitekturo Univerze v Mariboru
ISSN:1854-0171
COBISS.SI-ID:215987712 New window

Secondary language

Language:Slovenian
Title:Raziskave seizmičnega vpliva lokalnih tal na območju Brežic z metodo mikrotremorjev
Abstract:Širše območje Brežic je eno potresno najbolj dejavnih v Sloveniji. Potres z ML=5.7, ki je najbolj prizadel Brežice, se je zgodil 1917 in je dosegel največjo intenziteto VIII MSK. Seizmične vplive lokalnih tal zaradi kvartarnih sedimentov lahko pričakujemo na celotnem območju mesta. Ker je za oceno vpliva lokalnih tal na voljo zelo malo podatkov vrtin in geofizikalnih raziskav, smo izvedli študijo z metodo spektralnega razmerja vodoravnih in navpične komponente (HVSR) mikrotremorjev v 113 merskih točkah na prostem površju. Na splošnem smo dobili jasne spektralne vrhove, nekaj pa je bilo tudi območij s sploščeno krivuljo spektralnega razmerja, ki kaže na majhen kontrast v akustični impedanci med sedimenti in skalno podlago. Izrisana karta resonančne frekvence sedimentov kaže frekvenčni razpon 1-15 Hz. V južnem delu mesta odražajo višje frekvence tanko plast sedimentov (Brežiška terasa in srednja Savska terasa). Visoke amplitude HVSR vrhov kažejo na velik impedančni kontrast s sarmatijsko ali badenijsko podlago. Za severni del so značilne nizke frekvence, ki kažejo na debelo plast plio-kvartarnih sedimentov in majhen impedančni kontrast s pontijskim laporjem. Prehod med območjem višjih in nižjih frekvenc je razmeroma strm. Dodatno smo izvedli meritve v dvanajstih značilnih hišah za določitev vzdolžne in prečne frekvence stavbe. Ugotovljeno frekvenčno območje 5-10 Hz kaže na nekaj območij v južnem delu mesta, kjer obstoja potencialna nevarnost za resonanco med tlemi in objekti. Za dve stavbi smo neposredno ugotovili možnost takšne resonance. Glede na opravljene raziskave lahko pričakujemo bolj izrazite lokalne seizmične učinke v južnem delu Brežic.
Keywords:vibracije tal, mikrotremorji, spektralno razmerje med vodoravnima in navpično komponento (HVSR), seizmični vpliv lokalnih tal, resonanca med tlemi in objektom


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