Assessment of the Seismic Site Amplification in the City of Ivanec (NW Part of Croatia) Using the Microtremor HVSR Method and Equivalent-Linear Site Response Analysis

Abstract

The city of Ivanec is located between valley of the Bednja River and Mt. Ivanščica and this area can be prone to significant seismic site amplification due to local site characteristics. This study presents the first assessment of seismic site amplification for the city of Ivanec by the microtremor horizontal-to-vertical-spectral-ratio (HVSR) method and the equivalent-linear (EQL) site response analysis. Based on microtremor measurements and HVSR analysis, fundamental soil frequency and HVSR peak amplitude maps indicate potentially seismic danger zones. The 1-D EQL site response analysis was performed using multiple suites of earthquake ground motions scaled to the 95-and 475-year return periods of peak ground accelerations. Site amplification maps at the predominant peak frequency and ground surface indicate two microzones, one with high amplification in the central part of the city due to soft soil characteristics, and the other with small amplification in the transitional zone from alluvial basin towards the foothills of Mt. Ivanščica. HVSR peak amplitudes and site response peak amplifications showed similar spatial distributions with similar predominant peak frequencies but with different amplitude levels. Site amplification maps provided significant information about potential resonance effects for structures of certain heights that can be correlated with the local ground shaking characteristics.

Mapping the thickness of Quaternary sediments in the Iska alluvial fan (central Slovenia) using microtremor method

“…4, T115 and T154) it was still possible to derive the sediment frequency with the study of the MHVSR curve peak amplitude and by examining the Fourier (amplitude) spectra. Additionally, peak frequencies were compared to those of the surrounding measurements (Stanko et al, 2019). The main reasons for the failure of the above criteria were a high level of lowfrequency noise disturbances during the whole 20 min of acquisition or the presence of several peaks in the spectrum.…”

An overview of seismic ground response methods over the world and their applications in Vietnam

“…Many questions have been raised about the feasibility of the more than 50-year-old theory. In fact, this theory is still appropriate for earthquake response of horizontal layers in the modern analysis [Groholski et al, 2015[Groholski et al, , 2016Fiorentino et al, 2018;Yamin et al, 2018, Stanko et al, 2019. The reason is that due to the simplicity of the program , the input and output data are the text file or spreadsheet and more crucially the working time of program to get site response is quite fast (just in seconds).…”

“…The other methods either combine the numerical earthquake models and the observation [Chávez-García et al, 2000;Chávez-García , 2003 ] ; or compare the results from the hybrid modelling in the frequency domain with the results obtained from experimental data [Riepl et al, 2000]; or combine the finite element method with the boundary element method to solve problem of homogeneous and non-homogeneous topographic structures subjected to incident in-plane motions [Kamalian et al, 2006]; or use the stochastic method proposed by Boore [ 2003] ; or apply the analytical model proposed by Mavroeidis and Papageorgiou [2003] to study about the bed rock and ground surface acceleration of the considered region [ Ebrahimian, 2013 ] ; or estimate seismic site amplification using microtremor measurements and HVSR analysis combined with 1D equivalent-linear site response analysis for different peak ground accelerations [Stanko et al, 2019].…”

Ground vulnerability derived from the horizontal‐to‐vertical spectral ratio: Comparison with the damage distribution caused by the 2017 ML 5.4 Pohang earthquake, Korea

“…Previous studies suggest that the HVSR method is useful for identifying the peak frequencies of the site response (e.g., Lachet et al, 1996;Bonilla et al, 1997;Mucciarelli et al, 2003;Salinas et al, 2014;Mihaylov et al, 2016). However, there is less certainty regarding application of the method to assess amplification (e.g., Stanko et al, 2019). Although the theoretical basis of the method remains controversial, empirical evaluation demonstrates that the HVSR method provides a lower bound on the true amplification level (e.g., Haghshenas et al, 2008).…”