Naslov
Equivalent-linear site response analysis on the site of the historical Trakošćan Castle, Croatia using HVSR method

Autori
Stanko, Davor ; Markušić, Snježana ; Strelec, Stjepan ; Gazdek, Mario

Izvornik
Environmental Earth Sciences (1866-6280) 76 (2017); 642, 21

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Local site effects ; Seismic vulnerability ; Horizontal-to-Vertical Spectral Ratio ; Equivalent-Linear analysis ; Site response analysis ; Historical monuments

Sažetak
This paper presents a major extension of seismic vulnerability research project on the site of Trakošćan Castle based on the initial Horizontal- to-Vertical-Spectral-Ratio (HVSR) results from Stanko et al. (2016). The estimated HVSR site frequencies and HV amplification at Trakošćan Castle can only be used as an indication of the initial soil site frequency and amplification, so- called “natural soil model”, corresponding to the subsoil profile without the influence of an earthquake. The Equivalent-Linear (EQL) site response analysis has been carried out for different earthquake scenarios for a maximum input rock peak ground acceleration (PGAROCK) that corresponds to return periods of 95 (0.08 g), 475 (0.18 g) and 1000 years (0.31 g). The aim of the research is to evaluate structural seismic design responses and to determine type and degree of damage caused by local site effect, which is the results of an alluvial basin and topographic influences. The main objective of this research is the formation of local microseismic zones based on an EQL analysis: surface spectral acceleration and amplification maps at the predominant frequency. Based on the HVSR frequency response of the core structure of Trakošćan Castle and the Tower itself (fundamental and higher frequency modes), maps of surface spectral acceleration and soil amplification at different frequencies (3 Hz, 5 Hz and 10 Hz) are developed for different input PGAROCK levels (0.08 g, 0.18 g and 0.31 g) to evaluate seismic response of the Castle. Observed amplifications are correlated with ground motion polarization and directionality of the ground motion from the alluvial basin to the hilltop. Shortening of predominant frequencies (lengthening of the period), particularly in the alluvial basin, has been observed with higher input PGAROCK in the EQL analysis. This effect is not manifested in the Trakošćan hill and predominant frequencies match HVSR frequencies. The use of certain geophysical survey methods at historical sites is a big problem, because terrain features (e.g. steep hills, mountains, ridges, slopes, cliffs etc.) create lack of space and make it impossible to carry out a research. Microtremor measurements at historical sites can overcome this limitation and provide local seismic response and vulnerability behaviour of historical monuments without destroying their authenticity. Also, computational modelling can greately improve the results. The EQL site response analysis on the site of Trakošćan Castle has confirmed and improved the results of seismic response and vulnerability based on HVSR method.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Geofizika, Građevinarstvo, Rudarstvo, nafta i geološko inženjerstvo, Temeljne tehničke znanosti

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